Indications : Asthma; Bronchitis, chronic; Emphysema
Pregnancy Category C
WHO Formulary Top 200 Drugs
FDA Approved 1979 Apr
DRUG CLASS : Antisthmatics
BRAND NAMES : Accurbron (US); Aerobin (Germany); Aerodyne Retard (Austria); Aerolate (US); Afonilum Mite (Germany); Afonilum Forte (Germany); Afonilum Retard (Germany); Almarion (Thailand); Aloefilina *; Amilex (Indonesia); Aminomal *; Aquaphyllin (US); Armophylline (France); Asmalix (US); Asmasalon (Philippines); Asperal *; Asperal-T (Belgium); Austyn (Australia, Korea); Bilordyl *; Bronchoretard (Germany); Bronkodyl (US); Bronsolvan (Indonesia); Bykofilin *; Constant-T (US); Cronasma (Germany); Diffumal (Bahrain, Cyprus, Egypt, Iran, Iraq, Jordan, Kuwait, Lebanon, Libya, Oman, Qatar, Republic-of-Yemen, Saudi-Arabia, Syria, United-Arab-Emirates); Elixicon (US); Elixofilina (Mexico, Peru); Elixomin (US); Elixophyllin (US); Euphyllin Retard (Benin, Burkina-Faso, Ethiopia, Gambia, Ghana, Guinea, Ivory-Coast, Kenya, Liberia, Malawi, Mali, Mauritania, Mauritius, Morocco, Niger, Nigeria, Senegal, Seychelles, Sierra-Leone, South-Africa, Sudan, Tanzania, Tunia, Uganda, Zambia, Zimbabwe); Euphylong (Bahrain, Cyprus, Egypt, Iran, Iraq, Jordan, Kuwait, Lebanon, Libya, Oman, Qatar, Republic-of-Yemen, Saudi-Arabia, Syria, United-Arab-Emirates, Hong-Kong); Euphylong Retardkaps (Germany); Euphylong SR (Philippines); Godafilin (Spain); Hydro-Spec (US); Labid (US); Lanophyllin (US); Lasma (Bahrain, Cyprus, Egypt, Iran, Iraq, Jordan, Kuwait, Lebanon, Libya, Oman, Qatar, Republic-of-Yemen, Saudi-Arabia, Syria, United-Arab-Emirates, England); Lixolin (US); Nefoben (Argentina); Neulin-SA *; Neulin-SR (Taiwan); Neulin SA (South-Africa); Nuelin (Australia, New-Zealand; Bahamas, Barbados, Belize, Bermuda, Curacao, Guyana, Jamaica, Netherland-Antilles, Surinam, Trinidad, Denmark, Finland, Norway, Costa-Rica, Dominican-Republic, El-Salvador, Honduras, Panama, Malaysia, Philippines); Nuelin SA (Benin, Burkina-Faso, Ethiopia, Gambia, Ghana, Guinea, Ivory-Coast, Kenya, Liberia, Malawi, Mali, Mauritania, Mauritius, Morocco, Niger, Nigeria, Senegal, Seychelles, Sierra-Leone, Sudan, Tanzania, Tunia, Uganda, Zambia, Zimbabwe; Bahrain, Cyprus, Egypt, Iran, Iraq, Jordan, Kuwait, Lebanon, Libya, Oman, Qatar, Republic-of-Yemen, Saudi-Arabia, Syria, United-Arab-Emirates, Costa-Rica, Dominican-Republic, El-Salvador, Guatemala, Honduras, Panama); Nuelin SR (Bahrain, Cyprus, Egypt, Iran, Iraq, Jordan, Kuwait, Lebanon, Libya, Oman, Qatar, Republic-of-Yemen, Saudi-Arabia, Syria, United-Arab-Emirates, Australia, Hong-Kong, Malaysia, Thailand); Pharphylline (Netherlands); Phyllocontin *; Phylobid (Benin, Burkina-Faso, Ethiopia, Gambia, Ghana, Guinea, Ivory-Coast, Kenya, Liberia, Malawi, Mali, Mauritania, Mauritius, Morocco, Niger, Nigeria, Senegal, Seychelles, Sierra-Leone, Sudan, Tanzania, Tunia, Uganda, Zambia, Zimbabwe, India); Provent *; Pulmidur (Austria, Germany); Pulmo *; Pulmo (US); Quibron T SR (Canada, Indonesia, Thailand); Respbid (US); Slo-Bid (US); Slo-Phyllin (US); Solosin (Germany); Solu-Phyllin (US); Somofillina (Italy); Somophyllin (US); Sustaire (US); T-Phyl (US); Talofren *; Talotren (Mexico); Teobid (Colombia); Teoclear (Korea); Teoclear LA (Argentina); Teofilina *; Teofilina Retard (Colombia); Teolixir (Spain); Teolong (Mexico); Teophyllin *; Teosona (Argentina); Theo-2 (Belgium); Theo-24 (US); Theo-Bros (Greece); Theo-Dur (US); Theo-Time (US); Theo PA (India); Theobid (US); Theochron (US); Theoclear (US); Theocontin (US); Theocot (US); Theolair (US); Theolair S (Peru); Theolair S.R. (Mexico); Theolan (Taiwan, Korea); Theomar (US); Theomax (Spain); Theon (Switzerland); Theophyl (US); theophylline Anhydrous (US); Theoplus (Bulgaria, Spain); Theoplus Retard (Austria, Greece); Theosol-80 (US); Theospan Sr (US); Theospirex Retard (Switzerland, Austria); Theostat LP (France); Theostat 80 (US); Theotard (Israel); Theotrim (Israel); Theovent (US); Theovent LA (Hong-Kong); Theo von CT (Germany); Theox (US); Tiodilax (Argentina); Truxophyllin (US); Unicontin-400 Continus (India); Uni-Dur (US); Unifyl *; Unifyl Retard (Switzerland); Uniphyl (US); Uniphyllin (Taiwan); Uniphyllin Continus (Benin, Burkina-Faso, Ethiopia, Gambia, Ghana, Guinea, Ivory-Coast, Kenya, Liberia, Malawi, Mali, Mauritania, Mauritius, Morocco, Niger, Nigeria, Senegal, Seychelles, Sierra-Leone, Sudan, Tanzania, Tunia, Uganda, Zambia, Zimbabwe); Xantivent (Switzerland);
(International brand names outside U.S. in italics)
* Indicates foreign drugs without region specification at time of publication.
COST OF THERAPY : $ 67.89 (Asthma; Tablet; 200 mg; 3/day; 365 days)
HCFA JCODES : J2810 per 40 mg IV
DESCRIPTION :
theophylline is structurally classified as a methylxanthine. It occurs as a white, odorless, crystalline powder with a bitter taste. Anhydrous theophylline has the chemical name 1H-Purine-2,6-dione,3,7-dihydro-1,3-dimethyl-.
The molecular formula of anhydrous theophylline is C7H8N4O2 with a molecular weight of 180.17. (For products containing theophylline monohydrate, substitute the following: The molecular formula of theophylline monohydrate is C7H8N4O2H2O with a molecular weight of 198.18.)
The molecular formula of oxtriphylline is C12H21N5O3 with a molecular weight of 283.33.
Immediate-Release Oral Forms : Slo-Phyllin tablets (theophylline tablets) are scored, dye-free tablets providing 100 mg or 200 mg of theophylline, anhydrous.
Slo-Phyllin 80 mg Syrup (theophylline, anhydrous) is a nonalcoholic, sugar-free solution containing per 15 ml theophylline, anhydrous 80 mg with sodium benzoate, 18 mg and methylparaben, 3 mg added as preservatives.
Both tablets and syrup are intended for oral administration. theophylline is a bronchodilator structurally classified as a xanthine derivative.
Syrup inactive ingredients are citric acid, flavors, glycerine, methylparaben, propylene glycol, saccharin sodium, sodium benzoate, sorbitol, purified water.
Tablets: 100 mg inactive ingredients are lactose, magnesium stearate, microcrystalline cellulose, sodium starch glycolate; 200 mg inactive ingredients are magnesium stearate, microcrystalline cellulose, sodium starch glycolate.
Sustained Action Capsules : Theo-Dur Sprinkle sustained action capsules contain 50 mg, 75 mg, 125 mg, or 200 mg anhydrous theophylline, a bronchodilator structurally classified as a xanthine derivative. The inactive ingredients for Theo-Dur Sprinkle are: Ethylcellulose, hydroxypropylcellulose, povidone, and sucrose. Theo-Dur Sprinkle takes the form of long-acting microencapsulated beads within a hard gelatin capsule for oral administration.
The theophylline has been microencapsulated in a proprietary coating of polymers to mask the bitter taste associated with the drug while providing a prolonged effect. The entire contents of a Theo-Dur Sprinkle capsule are intended to be sprinkled on a small amount of soft food immediately prior to ingestion, or it may be swallowed whole. SUBDIVIDING THE CONTENTS OF A CAPSULE IS NOT RECOMMENDED. Each capsule is oversized to allow ease of opening.
Anhydrous theophylline is a white, odorless, crystalline powder having a bitter taste.
theophylline has two distinct actions in the airways of patients with reversible obstruction; smooth muscle relaxation (i.e., bronchodilation) and suppression of the response of the airways to stimuli (i.e., non-bronchodilator prophylactic effects). While the mechanisms of action of theophylline are not known with certainty, studies in animals suggest that bronchodilatation is mediated by the inhibition of two isozymes of phosphodiesterase (PDE III and, to a lesser extent, PDE IV) while non-bronchodilator prophylactic actions are probably mediated through one or more different molecular mechanisms, that do not involve inhibition of PDE III or antagonism of adenosine receptors. Some of the adverse effects associated with theophylline appear to be mediated by inhibition of PDE III (e.g., hypotension, tachycardia, headache, and emesis) and adenosine receptor antagonism (e.g., alterations in cerebral blood flow).
theophylline increases the force of contraction of diaphragmatic muscles. This action appears to be due to enhancement of calcium uptake through an adenosine-mediated channel.
Serum Concentration-Effect Relationship : Bronchodilation occurs over the serum theophylline concentration range of 5-20 mcg/ml. Clinically important improvement in symptom control has been found in most studies to require peak serum theophylline concentrations > 10 mcg/ml, but patients with mild disease may benefit from lower concentrations. At serum theophylline concentrations > 20 mcg/ml, both the frequency and severity of adverse reactions increase. In general, maintaining peak serum theophylline concentrations between 10 and 15 mcg/ml will achieve most of the drug’s potential therapeutic benefit while minimizing the risk of serious adverse events.
Pharmacokinetics
Overview : theophylline is rapidly and completely absorbed after oral administration in solution or immediate-release solid oral dosage form. theophylline does not undergo any appreciable pre-systemic elimination, distributes freely into fat-free tissues and is extensively metabolized in the liver.
The pharmacokinetics of theophylline vary widely among similar patients and cannot be predicted by age, sex, body weight or other demographic characteristics. In addition, certain concurrent illnesses and alterations in normal physiology (see TABLE 1) and co-administration of other drugs (see TABLE 2A and TABLE 2B) can significantly alter the pharmacokinetic characteristics of theophylline. Within-subject variability in metabolism has also been reported in some studies, especially in acutely ill patients. It is, therefore, recommended that serum theophylline concentrations be measured frequently in acutely ill patients (e.g., at 24-hr intervals) and periodically in patients receiving long-term therapy, e.g., at 6-12 month intervals. More frequent measurements should be made in the presence of any condition that may significantly alter theophylline clearance (see PRECAUTIONS, Laboratory Tests).
Note : In addition to the factors listed above, theophylline clearance is increased and half-life decreased by low carbohydrate/high protein diets, parenteral nutrition, and daily consumption of charcoal-broiled beef. A high carbohydrate/low protein diet can decrease the clearance and prolong the half-life of theophylline.
Absorption : theophylline is rapidly and completely absorbed after oral administration in solution or immediate-release solid oral dosage form. After a single dose of 5 mg/kg in adults, a mean peak serum concentration of about 10 mcg/ml (range 5-15 mcg/ml) can be expected 1-2 hr after the dose. Co-administration of theophylline with food or antacids does not cause clinically significant changes in the absorption of theophylline from immediate-release dosage forms.
Distribution : Once theophylline enters the systemic circulation, about 40% is bound to plasma protein, primarily albumin. Unbound theophylline distributes throughout body water, but distributes poorly into body fat. The apparent volume of distribution of theophylline is approximately 0.45 L/kg (range 0.3-0.7 L/kg) based on ideal body weight. theophylline passes freely across the placenta, into breast milk and into the cerebrospinal fluid (CSF). Saliva theophylline concentrations approximate unbound serum concentrations, but are not reliable for routine or therapeutic monitoring unless special techniques are used. An increase in the volume of distribution of theophylline, primarily due to reduction in plasma protein binding, occurs in premature neonates, patients with hepatic cirrhosis, uncorrected acidemia, the elderly and in women during the third trimester of pregnancy. In such cases, the patient may show signs of toxicity at total (bound + unbound) serum concentrations of theophylline in the therapeutic range (10-20 mcg/ml) due to elevated concentrations of the pharmacologically active unbound drug. Similarly, a patient with decreased theophylline binding may have a sub-therapeutic total drug concentration while the pharmacologically active unbound concentration is in the therapeutic range. If only total serum theophylline concentration is measured, this may lead to an unnecessary and potentially dangerous dose increase. In patients with reduced protein binding, measurement of unbound serum theophylline concentration provides a more reliable means of dosage adjustment than measurement of total serum theophylline concentration. Generally, concentrations of unbound theophylline should be maintained in the range of 6-12 mcg/ml.
Metabolism : Following oral dosing, theophylline does not undergo any measurable first-pass elimination. In adults and children beyond one year of age, approximately 90% of the dose is metabolized in the liver. Biotransformation takes place through demethylation to 1-methylxanthine and 3-methylxanthine and hydroxylation to 1,3-dimethyluric acid. 1-methylxanthine is further hydroxylated, by xanthine oxidase, to 1-methyluric acid. About 6% of a theophylline dose is N-methylated to caffeine. theophylline demethylation to 3-methylxanthine is catalyzed by cytochrome P-450 1A2, while cytochromes P-450 2E1 and P-450 3A3 catalyze the hydroxylation to 1,3-dimethyluric acid. Demethylation to 1-methylxanthine appears to be catalyzed either by cytochrome P-450 1A2 or a closely related cytochrome. In neonates, the N-demethylation pathway is absent while the function of the hydroxylation pathway is markedly deficient. The activity of these pathways slowly increases to maximal levels by one year of age.
Caffeine and 3-methylxanthine are the only theophylline metabolites with pharmacologic activity. 3-methylxanthine has approximately one tenth the pharmacologic activity of theophylline and serum concentrations in adults with normal renal function are <1 mcg/ml. In patients with end-stage renal disease, 3-methylxanthine may accumulate to concentrations that approximate the unmetabolized theophylline concentration. Caffeine concentrations are usually undetectable in adults regardless of renal function. In neonates, caffeine may accumulate to concentrations that approximate the unmetabolized theophylline concentration and thus, exert a pharmacologic effect. Both the N-demethylation and hydroxylation pathways of theophylline biotransformation are capacity-limited. Due to the wide intersubject variability of the rate of theophylline metabolism, non-linearity of elimination may begin in some patients at serum theophylline concentrations <10 mcg/ml. Since this non-linearity results in more than proportional changes in serum theophylline concentrations with changes in dose, it is advisable to make increases or decreases in dose in small increments in order to achieve desired changes in serum theophylline concentrations (see TABLE 4). Accurate prediction of dose-dependency of theophylline metabolism in patients a priori is not possible, but patients with very high initial clearance rates (i.e., low steady state serum theophylline concentrations at above average doses) have the greatest likelihood of experiencing large changes in serum theophylline concentration in response to dosage changes.
Excretion : In neonates, approximately 50% of the theophylline dose is excreted unchanged in the urine. Beyond the first three months of life, approximately 10% of the theophylline dose is excreted unchanged in the urine. The remainder is excreted in the urine mainly as 1,3-dimethyluric acid (35-40%), 1-methyluric acid (20-25%) and 3-methylxanthine (15-20%). Since little theophylline is excreted unchanged in the urine and since active metabolites of theophylline (i.e., caffeine, 3-methylxanthine) do not accumulate to clinically significant levels even in the face of end-stage renal disease, no dosage adjustment for renal insufficiency is necessary in adults and children >3 months of age. In contrast, the large fraction of the theophylline dose excreted in the urine as unchanged theophylline and caffeine in neonates requires careful attention to dose reduction and frequent monitoring of serum theophylline concentrations in neonates with reduced renal function (See WARNINGS).
Serum Concentrations at Steady State : After multiple doses of theophylline, steady state is reached in 30-65 hours (average 40 hours) in adults. At steady state, on a dosage regimen with 6-hour intervals, the expected mean trough concentration is approximately 60% of the mean peak concentration, assuming a mean theophylline half-life of 8 hours. The difference between peak and trough concentrations is larger in patients with more rapid theophylline clearance. In patients with high theophylline clearance and half-lives of about 4-5 hours, such as children age 1 to 9 years, the trough serum theophylline concentration may be only 30% of peak with a 6-hour dosing interval. In these patients a slow release formulation would allow a longer dosing interval (8-12 hours) with a smaller peak/trough difference.
Special Populations
See TABLE 1 for mean clearance and half, life values.
Geriatric : The clearance of theophylline is decreased by an average of 30% in healthy elderly adults (>60 yrs) compared to healthy young adults. Careful attention to dose reduction and frequent monitoring of serum theophylline concentrations are required in elderly patients(see WARNINGS).
Pediatrics : The clearance of theophylline is very low in neonates(see WARNINGS). theophylline clearance reaches maximal values by one year of age, remains relatively constant until about 9 years of age and then slowly decreases by approximately 50% to adult values at about age 16. Renal excretion of unchanged theophylline in neonates amounts to about 50% of the dose, compared to about 10% in children older than three months and in adults. Careful attention to dosage selection and monitoring of serum theophylline concentrations are required in pediatric patients (see WARNINGS and DOSAGE AND ADMINISTRATION).
Gender : Gender differences in theophylline clearance are relatively small and unlikely to be of clinical significance. Significant reduction in theophylline clearance, however, has been reported in women on the 20th day of the menstrual cycle and during the third trimester of pregnancy.
Race : Pharmacokinetic differences in theophylline clearance due to race have not been studied.
Renal Insufficiency : Only a small fraction, e.g., about 10%, of the administered theophylline dose is excreted unchanged in the urine of children greater than three months of age and adults. Since little theophylline is excreted unchanged in the urine and since active metabolites of theophylline (i.e., caffeine, 3-methylxanthine) do not accumulate to clinically significant levels even in the face of end-stage renal disease, no dosage adjustment for renal insufficiency is necessary in adults and children >3 months of age. In contrast, approximately 50% of the administered theophylline dose is excreted unchanged in the urine in neonates. Careful attention to dose reduction and frequent monitoring of serum theophylline concentrations are required in neonates with decreased renal function (see WARNINGS).
Hepatic Insufficiency : theophylline clearance is decreased by 50% or more in patients with hepatic insufficiency (e.g., cirrhosis, acute hepatitis, cholestasis). Careful attention to dose reduction and frequent monitoring of serum theophylline concentrations are required in patients with reduced hepatic function (see WARNINGS).
Congestive Heart Failure (CHF) : theophylline clearance is decreased by 50% or more in patients with CHF. The extent of reduction in theophylline clearance in patients with CHF appears to be directly correlated to the severity of the cardiac disease. Since theophylline clearance is independent of liver blood flow, the reduction in clearance appears to be due to impaired hepatocyte function rather than reduced perfusion. Careful attention to dose reduction and frequent monitoring of serum theophylline concentrations are required in patients with CHF (see WARNINGS).
Smokers : Tobacco and marijuana smoking appears to increase the clearance of theophylline by induction of metabolic pathways. theophylline clearance has been shown to increase by approximately 50% in young adult tobacco smokers and by approximately 80% in elderly tobacco smokers compared to non-smoking subjects. Passive smoke exposure has also been shown to increase theophylline clearance by up to 50%. Abstinence from tobacco smoking for one week causes a reduction of approximately 40% in theophylline clearance. Careful attention to dose reduction and frequent monitoring of serum theophylline concentrations are required in patients who stop smoking (see WARNINGS). Use of nicotine gum has been shown to have no effect on theophylline clearance.
Fever : Fever, regardless of its underlying cause, can decrease the clearance of theophylline. The magnitude and duration of the fever appear to be directly correlated to the degree of decrease of theophylline clearance. Precise data are lacking, but a temperature of 39°C (102°F) for at least 24 hours is probably required to produce a clinically significant increase in serum theophylline concentrations. Children with rapid rates of theophylline clearance (i.e., those who require a dose that is substantially larger than average [e.g., >22 mg/kg/day] to achieve a therapeutic peak serum theophylline concentration when afebrile) may be at greater risk of toxic effects from decreased clearance during sustained fever. Careful attention to dose reduction and frequent monitoring of serum theophylline concentrations are required in patients with sustained fever (see WARNINGS).
Miscellaneous
Other factors associated with decreased theophylline clearance include the third trimester of pregnancy, sepsis with multiple organ failure, and hypothyroidism. Careful attention to dose reduction and frequent monitoring of serum theophylline concentrations are required in patients with any of these conditions (see WARNINGS). Other factors associated with increased theophylline clearance include hyperthyroidism and cystic fibrosis.
In patients with chronic asthma, including patients with severe asthma requiring inhaled corticosteroids or alternate-day oral corticosteroids, many clinical studies have shown that theophylline decreases the frequency and severity of symptoms, including nocturnal exacerbations, and decreases the “as needed” use of inhaled beta-2 agonists. theophylline has also been shown to reduce the need for short courses of daily oral prednisone to relieve exacerbations of airway obstruction that are unresponsive to bronchodilators in asthmatics.
In patients with chronic obstructive pulmonary disease (COPD), clinical studies have shown that theophylline decreases dyspnea, air trapping, the work of breathing, and improves contractility of diaphragmatic muscles with little or no improvement in pulmonary function measurements.
Theophylline Sustained Action Capsules
In two-separate single-dose studies utilizing different subjects, the following bioavailability variables were observed. Theo-Dur Sprinkle administered in a 500-mg dose as pellets on applesauce to 6 healthy adults produced mean peak theophylline serum levels of 9.03 ± 2.59 mcg/ml at 8.67 ± 1.03 hours following administration. Administration of two lots of Theo-Dur Sprinkle as intact capsules in a 600-mg dose to 6 healthy adults produced mean peak theophylline serum levels of 9.08 ±1.30 mcg/ml and 7.60 ± 0.95 mcg/ml at 8.33 ± 1.50 and 8.67 ± 3.01 hours after administration, respectively. In these studies, Theo-Dur Sprinkle exhibited complete bioavailability when compared with an immediate release product. In both of these studies, the subjects fasted for 10 hours prior to dosing and for 4 hours after dosing.
In a multiple-dose, two-way, crossover study with 18 healthy, normal adults, the bioavailability from Theo-Dur Sprinkle administered as intact capsules was evaluated using Theo-Dur Sustained Action Tablets as the reference products. Fifteen subjects received 400 mg at 7:00 AM and 7:00 PM while 3 subjects received 200 mg because of low theophylline clearance. All meals and snacks were provided to the subjects during the course of this study, with breakfast at 9:00 AM, lunch at 12:30 PM, a snack at 3:00 PM, and dinner at 9:00 PM. Theo-Dur Sprinkle produced mean Cmax and Cmin theophylline serum levels of 10.4 ± 2.6 and 6.9 ± 1.8 mcg/ml as compared with a Cmax and Cmin of 10.5 ± 2.8 and 7.5 ± 2.7 mcg/ml for Theo-Dur tablets. The mean percent fluctuation normalized to Css was 38.8± 8.5% for Theo-Dur Sprinkle and 33.4 ± 9.7% for Theo-Dur Tablets (% fluctuation = 100 (Cmax-Cmin)/Css, where Css = AUC0-12/dosing interval). The mean percent fluctuation when normalized to Cmin was 51.9 ± 15.4% for Theo-Dur Sprinkle and 43.9 ± 17.4% for Theo-Dur Tablets (% fluctuation = 100 (Cmax-Cmin)/Cmin). The average peak-trough differences over 12 hours for Theo-Dur Sprinkle and Theo-Dur tablets were 3.5 ± 1.2 and 3.0 ± 0.7 mcg/ml, respectively. The AUC for Theo-Dur Sprinkle was 108.4 ± 26.0 while that for Theo-Dur tablets was 112.1 ± 32.5 mcg/hr/ml. In a separate study, Theo-Dur showed complete bioavailability when compared with an immediate-release product. This would suggest that bioavailability from Theo-Dur Sprinkle was complete and not statistically different from that of Theo-Dur tablets.
INDICATIONS AND USAGE :
theophylline is indicated for the treatment of the symptoms and reversible airflow obstruction associated with chronic asthma and other chronic lung diseases, e.g., emphysema and chronic bronchitis.
This product is contraindicated in individuals who have shown hypersensitivity to its components. It is also contraindicated in patients with active peptic ulcer disease, and in individuals with underlying seizure disorders (unless receiving appropriate anti-convulsant medication).
Concurrent Illness : theophylline should be used with extreme caution in patients with the following clinical conditions due to the increased risk of exacerbation of the concurrent condition: Active peptic ulcer disease, seizure disorders and cardiac arrhythmias (not including bradyarrhythmias).
Conditions That Reduce theophylline Clearance : There are several readily identifiable causes of reduced theophylline clearance. If the total daily dose is not appropriately reduced in the presence of these risk factors, severe and potentially fatal theophylline toxicity can occur. Careful consideration must be given to the benefits and risks of theophylline use and the need for more intensive monitoring of serum theophylline concentrations in patients with the following risk factors:
Age : Neonates (term and premature), Children <1 year, Elderly (>60 years)
Concurrent Diseases : Acute pulmonary edema, Congestive heart failure, Cor-pulmonale, Fever; 
102° for 24 hours or more; or lesser temperature elevations for longer periods, Hypothyroidism, Liver disease; cirrhosis, acute hepatitis, Reduced renal function in infants <3 months of age, Sepsis with multi-organ failure, Shock
When Signs or Symptoms of theophylline Toxicity Are Present
Whenever a patient receiving theophylline develops nausea or vomiting, particularly repetitive vomiting, or other signs or symptoms consistent with theophylline toxicity (even if another cause may be suspected), additional doses of theophylline should be withheld and a serum theophylline concentration measured immediately. Patients should be instructed not to continue any dosage that causes adverse effects and to withhold subsequent doses until the symptoms have resolved, at which time the clinician may instruct the patient to resume the drug at a lower dosage (see TABLE 4).
Dosage Increases : Increases in the dose of theophylline should not be made in response to an acute exacerbation of symptoms of chronic lung disease since theophylline provides little added benefit to inhaled beta2-selective agonists and systemically administered corticosteroids in this circumstance and increases the risk of adverse effects. A peak steady-state serum theophylline concentration should be measured before increasing the dose in response to persistent chronic symptoms to ascertain whether an increase in dose is safe. Before increasing the theophylline dose on the basis of a low serum concentration, the clinician should consider whether the blood sample was obtained at an appropriate time in relationship to the dose and whether the patient has adhered to the prescribed regimen (see PRECAUTIONS, Laboratory Tests).
As the rate of theophylline clearance may be dose-dependent (i.e., steady-state serum concentrations may increase disproportionately to the increase in dose), an increase in dose based upon a sub-therapeutic serum concentration measurement should be conservative. In general, limiting dose increases to about 25% of the previous total daily dose will reduce the risk of unintended excessive increases in serum theophylline concentration (see TABLE 4).
Serum levels above 20 mcg/ml are rarely found after appropriate administration of the recommended doses. However, in individuals in whom theophylline plasma clearance is reduced for any reason , even conventional doses may result in increased serum levels and potential toxicity.
Reduced theophylline clearance has been documented in the following readily identifiable groups: 1) patients with impaired liver function; 2) patients over 55 years of age, particularly males and those with chronic lung disease; 3) those with cardiac failure from any cause; 4) patients with sustained high fever; 5) neonates and infants under 1 year of age; and 6) patients taking certain drugs (see DRUG INTERACTIONS). Frequently, such patients have markedly prolonged theophylline serum levels following discontinuation of the drug.
Reduction of dosage and laboratory monitoring is especially appropriate in the above individuals.
Serious side effects such as ventricular arrhythmias, convulsions or even death may appear as the first sign of toxicity without any previous warning. Less serious signs of theophylline toxicity (i.e., nausea and restlessness) may occur frequently when initiating therapy, but are usually transient. When such signs are persistent during maintenance therapy, they are often associated with serum concentrations above 20 mcg/ml.
Stated differently, serious toxicity is not reliably preceded by less severe side effects. A serum concentration measurement is the only reliable method of predicting potentially life-threatening toxicity.
Many patients who require theophylline exhibit tachycardia due to their underlying disease process so that the cause/effect relationship to elevated serum theophylline concentrations may not be appreciated.
theophylline products may cause dysrhythmia and/or worsen pre-existing arrhythmias and any significant change in rate and/or rhythm warrants monitoring and further investigation.
Studies in laboratory animals (minipigs, rodents, and dogs) recorded the occurrence of cardiac arrhythmias and sudden death (with histologic evidence of myocardial necrosis) when beta-agonists and methylxanthines were administered concurrently. The significance of these findings when applied to humans is currently unknown.
Careful consideration of the various interacting drugs and physiologic conditions that can alter theophylline clearance and require dosage adjustment should occur prior to initiation of theophylline therapy, prior to increases in theophylline dose, and during follow up (see WARNINGS). The dose of theophylline selected for initiation of therapy should be low and, if tolerated , increased slowly over a period of a week or longer with the final dose guided by monitoring serum theophylline concentrations and the patient’s clinical response (see DOSAGE AND ADMINISTRATION).
Monitoring Serum theophylline Concentrations : Serum theophylline concentration measurements are readily available and should be used to determine whether the dosage is appropriate. Specifically, the serum theophylline concentration should be measured as follows:
1. When initiating therapy to guide final dosage adjustment after titration.
2. Before making a dose increase to determine whether the serum concentration is sub-therapeutic in a patient who continues to be symptomatic.
3. Whenever signs or symptoms of theophylline toxicity are present.
4. Whenever there is a new illness, worsening of a chronic illness or a change in the patient’s treatment regimen that may alter theophylline clearance (e.g., fever >102°F sustained for 24 hours, hepatitis, or drugs listed in TABLE 2 are added or discontinued).
To guide a dose increase, the blood sample should be obtained at the time of the expected peak serum theophylline concentration; 1-2 hours after a dose at steady-state. For most patients, steady-state will be reached after 3 days of dosing when no doses have been missed, no extra doses have been added, and none of the doses have been taken at unequal intervals. A trough concentration (i.e., at the end of the dosing interval) provides no additional useful information and may lead to an inappropriate dose increase since the peak serum theophylline concentration can be two or more times greater than the trough concentration with an immediate-release formulation. If the serum sample is drawn more than two hours after the dose, the results must be interpreted with caution since the concentration may not be reflective of the peak concentration. In contrast, when signs or symptoms of theophylline toxicity are present, the serum sample should be obtained as soon as possible, analyzed immediately, and the result reported to the clinician without delay. In patients in whom decreased serum protein binding is suspected (e.g., cirrhosis, women during the third trimester of pregnancy), the concentration of unbound theophylline should be measured and the dosage adjusted to achieve an unbound concentration of 6-12 mcg/ml.
Saliva concentrations of theophylline cannot be used reliably to adjust dosage without special techniques.
Extended-Release Capsules
THE CONTENTS OF A THEO-DUR SPRINKLE CAPSULE SHOULD NOT BE CHEWED OR CRUSHED.
General : On the average, theophylline half-life is shorter in cigarette and marijuana smokers than in non-smokers, but smokers can have half-lives as long as non-smokers. theophylline should not be administered concurrently with other xanthine medications. Use with caution in patients with hypoxemia, hypertension or those with history of peptic ulcer. theophylline preparations should be used cautiously in patients with history of peptic ulcer. theophylline may occasionally act as a local irritant to the GI tract; although gastrointestinal symptoms are more commonly centrally mediated and associated with serum drug concentrations over 20 mcg/ml.
Immediate Release Products : As a result of its pharmacological effects, theophylline at serum concentrations within the 10-20 mcg/ml range modestly increases plasma glucose (from a mean of 88 mg% to 98 mg%), uric acid (from a mean of 4 mg/dl to 6 mg/dl), free fatty acids (from a mean of 451 q/l to 800 q/l, total cholesterol (from a mean of 140 vs 160 mg/dl), HDL (from a mean of 36 to 50 mg/dl), HDL/LDL ratio (from a mean of 0.5 to 0.7), and urinary free cortisol excretion (from a mean of 44 to 63 mcg/24 hr). theophylline at serum concentrations within the 10-20 mcg/ml range may also transiently decrease serum concentrations of triiodothyronine (144 before, 131 after one week and 142 ng/dl after 4 weeks of theophylline). The clinical importance of these changes should be weighed against the potential therapeutic benefit of theophylline in individual patients.
Extended-Release Capsules : Serum levels should be monitored periodically to determine the theophylline level associated with observed clinical response and as the method of predicting toxicity. For such measurements, the serum sample should be obtained at the time of peak concentration, (Immediate Release products: 1 to 2 hours after administration) 4-8 hours when medication is taken every 12 hours, or 3-6 hours when medication is taken every 8 hours. It is important that the patient has not missed or taken additional doses during the previous 48 hours and that dosing intervals were reasonably equally spaced. DOSAGE ADJUSTMENT BASED ON SERUM theophylline MEASUREMENTS WHEN THESE INSTRUCTIONS HAVE NOT BEEN FOLLOWED MAY RESULT IN RECOMMENDATIONS THAT PRESENT RISK OF TOXICITY TO THE PATIENT.
Information for the Patient
Immediate Release Products : The patient (or parent/care giver) should be instructed to seek medical advice whenever nausea, vomiting, persistent headache, insomnia r rapid heart beat occurs during treatment with theophylline, even if another cause is suspected. The patient should be instructed to contact their clinician if they develop a new illness, especially if accompanied by a persistent fever, if they experience worsening of a chronic illness, if they start or stop smoking cigarettes or marijuana, or if another clinician adds a new medication or discontinues a previously prescribed medication. Patients should be instructed to inform all clinicians involved in their care that they are taking theophylline, especially when a medication is being added or deleted from their treatment. Patients should be instructed to not alter the dose, timing of the dose, or frequency of administration without first consulting their clinician. If a dose is missed, the patient should be instructed to take the next dose at the usually scheduled time and to not attempt to make up for the missed dose.
Extended-Release Capsules : This information is intended to aid in the safe and effective use of this medication. It is not a disclosure of all possible adverse or intended effects.
The physician should reinforce the importance of taking only the prescribed dose and the time interval between doses. As with any controlled-release theophylline product, the patient should alert the physician of symptoms occur repeatedly, especially near the end of the dosing interval.
When prescribing administration by the sprinkle method, details of the proper technique should be explained to patient (see DOSAGE AND ADMINISTRATION, Sprinkling Contents on Food).
Patients should be informed of the need to take this drug in the fasting state, and that drug administration should be 1 hour before or 2 hours after meals (see DOSAGE AND ADMINISTRATION).
Carcinogenesis, Mutagenesis, and Impairment of Fertility
Immediate Release Products : Long term carcinogenicity studies have been carried out in mice (oral doses 30-150 mg/kg)and rats (oral doses 5-75 mg/kg). Results are pending. theophylline has been studied in Ames salmonella, in vivo and in vitro cytogenetics, micronucleus and Chinese hamster ovary test systems and has not been shown to be genotoxic. In a 14 week continuous breeding study, theophylline, administered to mating pairs of B6C3F1 mice at oral doses of 120, 270 and 500 mg/kg (approximately 1.0-3.0 times the human dose on a mg/m2 basis) impaired fertility, as evidenced by decreases in the number of live pups per litter, decreases in the mean umber of litters per fertile pair, and increases in the gestation period at the high dose as well as decreases in the proportion of pups born alive at the mid and high dose. In 13 week toxicity studies, theophylline was administered to F344 rats and B6C3F1 mice at oral doses of 40-300 mg/kg (approximately 2.0 times the human dose on a mg/m2 basis). At the high dose, systemic toxicity was observed in both species including decreases in testicular weight.
Extended-Release Capsules : Long-term carcinogenicity studies have not been performed with theophylline. Chromosome-breaking activity was detected in human cell cultures at concentrations of theophylline up to 50 times the therapeutic serum concentration in humans. theophylline was not mutagenic in the dominant lethal assay in male mice given theophylline intraperitoneally in doses up to 30 times the maximum daily human oral dose.
Studies to determine the effect on fertility have not been performed with theophylline.
Pregnancy Category C
Immediate Release Products : There are no adequate and well controlled studies in pregnant women. Additionally, there are no teratogenicity studies in non-rodents (e.g., rabbits). theophylline was not shown to be teratogenic in CD-1 mice at oral doses up to 400 mg/kg, approximately 2.0 times the human dose on a mg/m2 basis or in CD-1 rats at oral doses up to 260 mg/kg, approximately 3.0 times the recommended human dose on a mg/m2 basis. At a dose of 220 mg/kg, embryotoxicity was observed in rats in the absence of maternal toxicity.
Extended-Release Capsules : Animal reproduction studies have not been conducted with theophylline. It is not known whether theophylline can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Xanthines should be given to a pregnant woman only if clearly needed.
Nursing Mothers
Immediate Release Products : theophylline is excreted into breast milk and may cause irritability or other signs of mild toxicity in nursing human infants. The concentration of theophylline in breast milk is about equivalent to the maternal serum concentration. An infant ingesting a liter of breast milk containing 10-20 mcg/ml of theophylline day is likely to receive 10-20 mg of theophylline per day. Serious adverse effects in the infant are unlikely unless the mother has toxic serum theophylline concentrations.
Extended-Release Capsules : theophylline is distributed into breast milk and may cause irritability or other signs of toxicity in nursing infants. Because of the potential of serious adverse reactions in nursing infants from theophylline, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.
Pediatric Use
Immediate Release Products : theophylline is safe and effective for the approved indications in pediatric patients (See INDICATIONS AND USAGE). The maintenance dose of theophylline must be selected with caution in pediatric patients since the rate of theophylline clearance is highly variable across the age range of neonates to adolescents (see CLINICAL PHARMACOLOGY, TABLE 1, WARNINGS, and DOSAGE AND ADMINISTRATION). Due to the immaturity of theophylline metabolic pathways in infants under the age of one year, particular attention to dosage selection and frequent monitoring of serum theophylline concentrations are required when theophylline is prescribed to pediatric patients in this age group.
Extended-Release Capsules : Safety and efficacy of Theo-Dur Sprinkle in children under 6 years of age have not been established with this product.
Safety and effectiveness of Theo-Dur Extended-Release Tablets administered:
2. Every 12 hours in children under 6 years of age, have not been established.
Geriatric Use
Elderly patients are at significantly greater risk of experiencing serious toxicity from theophylline than younger patients due to pharmacokinetic and pharmacodynamic changes associated with aging. theophylline clearance is reduced in patients greater than 60 years of age, resulting in increased serum theophylline concentrations in response to a given theophylline dose. Protein binding may be decreased in the elderly resulting in a larger proportion of the total serum theophylline concentration in the pharmacologically active unbound form. Elderly patients also appear to be more sensitive to the toxic effects of theophylline after chronic overdosage than younger patients. For these reasons, the maximum daily dose of theophylline in patients greater than 60 years of age ordinarily should not exceed 400 mg/day unless the patient continues to be symptomatic and the peak steady state serum theophylline concentration is <10 mcg/ml (see DOSAGE AND ADMINISTRATION). theophylline doses greater than 400 mg/d should be prescribed with caution in elderly patients.
theophylline interacts with a wide variety of drugs. The interaction may be pharmacodynamic, i.e., alterations in the therapeutic response to theophylline or another drug or occurrence of adverse effects without a change in serum theophylline concentration. More frequently, however, the interaction is pharmacokinetic, i.e., the rate of theophylline clearance is altered by another drug resulting in increased or decreased serum theophylline concentrations. theophylline only rarely alters the pharmacokinetics of other drugs.
The drugs listed in TABLE 2A and TABLE 2B have the potential to produce clinically significant pharmacodynamic or pharmacokinetic interactions with theophylline. The information in the “Effect” column of TABLE 2A and TABLE 2B assumes that the interacting drug is being added to a steady-state theophylline regimen. If theophylline is being initiated in a patient who is already taking a drug that inhibits theophylline clearance (e.g., cimetidine, erythromycin), the dose of theophylline required to achieve a therapeutic serum theophylline concentration will be smaller. Conversely, if theophylline is being initiated in a patient who is already taking a drug that enhances theophylline clearance (e.g., rifampin), the dose of theophylline required to achieve a therapeutic serum theophylline concentration will be larger. Discontinuation of a concomitant drug that increases theophylline clearance will result in accumulation of theophylline to potentially toxic levels, unless the theophylline dose is appropriately reduced. Discontinuation of a concomitant drug that inhibits theophylline clearance will result in decreased serum theophylline concentrations, unless the theophylline dose is appropriately increased.
The listing of drugs in TABLE 2A and TABLE 2B is current as of April 3, 1995. New interactions are continuously being reported for theophylline, especially with new chemical entities. The clinician should not assume that a drug does not interact with theophylline if it is not listed in TABLE 2A and TABLE 2B. Before addition of a newly available drug in a patient receiving theophylline, the package insert of the new drug and/or the medical literature should be consulted to determine if an interaction between the new drug and theophylline has been reported.
| Drug | Type of Interaction | Effect |
|---|---|---|
| Adenosine | theophylline blocks adenosine receptors | Higher doses of adenosine may be required to achieve desired effect |
| Alcohol | A single large dose of alcohol (3 ml/kg of whiskey) decreases theophylline clearance for up to 24 hours | 30% increase |
| Allopurinol | Decreases theophylline clearance at allopurinol doses 600 mg/day |
25% increase |
| Aminoglutethimide | Increases theophylline clearance by induction of microsomal enzyme activity | 25% decrease |
| Carbamazepine | Similar to aminoglutethimide | 30% decrease |
| Cimetidine | Decreases theophylline clearance by inhibiting cytochrome P450 1A2 | 70% increase |
| Ciprofloxacin | Similar to cimetidine | 40% increase |
| Clarithromycin | Similar to erythromycin | 25% increase |
| Diazepam | Benzodiazepines increase CNS concentrations of adenosine, a potent CNS depressant, while theophylline blocks adenosine receptors | Larger diazepam doses may be required to produce desired level of sedation |
| Discontinuation of theophylline without reduction of diazepam dose may result in respiratory depression | ||
| Disulfiram | Decreases theophylline clearance by inhibiting hydroxylation and demethylation | 50% increase |
| Enoxacin | Similar to cimetidine | 300% increase |
| Ephedrine | Synergistic CNS effects | Increased frequency of nausea, nervousness, and insomnia |
| Erythromycin | Erythromycin metabolite decreases theophylline clearance by inhibiting cytochrome P450 3A3 | 35% increase |
| Erythromycin steady-state serum concentrations decreased by a similar amount | ||
| Estrogen | Estrogen containing oral contraceptives decrease theophylline clearance in a dose-dependent fashion. The effect of progesterone on theophylline clearance is unknown | 30% increase |
| Flurazepam | Similar to diazepam | Similar to diazepam |
| Fluvoxamine | Similar to cimetidine myocardium to catecholamines, theophylline increases release of endogenous catecholamines | Similar to cimetidine ventricular arrhythmias |
| Interferon, human recombinant alpha-A | Decreases theophylline clearance | 100% increase |
| Isoproterenol (IV) | Increases theophylline clearance | 20% decrease |
| Ketamine | Pharmacologic | May lower theophylline seizure threshold |
| Lithium | theophylline increases renal lithium clearance | Lithium dose required to achieve a therapeutic serum concentration increased an average of 60% |
| Lorazepam | Similar to diazepam | Similar to diazepam |
| * Refer to DRUG INTERACTIONS for further information regarding table. | ||
| Average effect on steady state theophylline concentration or other clinical effect for pharmacologic interactions. Individual patients may experience larger changes in serum theophylline concentration than the value listed. |
||
| Drug | Type of Interaction | Effect |
|---|---|---|
| Methotrexate (MTX) | Decreases theophylline clearance. | 20% increase after low dose MTX, higher dose MTX may have a greater effect. |
| Mexiletine | Similar to disulfiram. | 80% increase |
| Midazolam | Similar to diazepam. | Similar to diazepam. |
| Moricizine | Increases theophylline clearance. | 25% decrease |
| Pancuronium | theophylline may antagonize non-depolarizing neuromuscular blocking effects; possibly due to phosphodiesterase inhibition. | Larger dose of pancuronium may be required to achieve neuromuscular blockade. |
| Pentoxifylline | Decreases theophylline clearance. | 30% increase |
| Phenobarbital (PB) | Similar to aminoglutethimide. | 25% decrease after two weeks of concurrent PB. |
| Phenytoin | Phenytoin increases theophylline clearance by increasing microsomal enzyme activity. theophylline decreases phenytoin absorption. | Serum theophylline and phenytoin concentrations decrease about 40%. |
| Propafenone | Decreases theophylline clearance and pharmacologic interaction. | 40% increase. Beta-2 blocking effect may decrease efficacy of theophylline. |
| Propranolol | Similar to cimetidine and pharmacologic interaction. | 100% increase. Beta-2 blocking effect may decrease efficacy of theophylline. |
| Rifampin | Increases theophylline clearance by increasing cytochrome P450 1A2 and 3A3 activity. | 20-40% decrease |
| Sulfinpyrazone | Increases theophylline clearance by increasing demethylation and hydroxylation. | 20% decrease |
| Decreases renal clearance of theophylline. | ||
| Tacrine | Similar to cimetidine, also increases renal clearance of theophylline. | 90% increase |
| Thiabendazole | Decreases theophylline clearance. | 190% increase |
| Ticlopidine | Decreases theophylline clearance. | 60% increase |
| Troleandomycin | Similar to erythromycin. | 33-100% increase depending on troleandomycin dose. |
| Verapamil | Similar to disulfiram. | 20% increase |
| * Refer to DRUG INTERACTIONS for further information regarding table. | ||
| Average effect on steady state theophylline concentration or other clinical effect for pharmacologic interactions. Individual patients may experience larger changes in serum theophylline concentration than the value listed. |
||
The Effect of Other Drugs on theophylline Serum Concentration Measurements : Most serum theophylline assays in clinical use are immunoassays which are specific for theophylline. Other xanthines such as caffeine, dyphylline, and pentoxifylline are not detected by these assays. Some drugs (e.g. , cefazolin, cephalothin), however, may interfere with certain HPLC techniques. Caffeine and xanthine metabolites in neonates or patients with renal dysfunction may cause the reading from some dry reagent office methods to be higher than the actual serum theophylline concentration.
Cessation of Smoking
Drug Interactions : Adding a drug that inhibits theophylline metabolism (e.g. , cimetidine, erythromycin, tacrine) or stopping a concurrently administered drug that enhances theophylline metabolism (e.g. , carbamazepine, rifampin). (see TABLE 2A and TABLE 2B).
Adverse reactions associated with theophylline are generally mild when peak serum theophylline concentrations are <20 mcg/ml and mainly consist of transient caffeine-like adverse effects such as nausea, vomiting, headache, and insomnia. When peak serum theophylline concentrations exceed 20 mcg/ml, however, theophylline produces a wide range of adverse reactions including persistent vomiting, cardiac arrhythmias, and intractable seizures which can be lethal (see OVERDOSAGE). The transient caffeine-like adverse reactions occur in about 50% of patients when theophylline therapy is initiated at doses higher than recommended initial doses (e.g., >300 mg/day in adults and >12 mg/kg/day in children beyond >1 year of age). During the initiation of theophylline therapy, caffeine-like adverse effects may transiently alter patient behavior, especially in school age children, but this response rarely persists. Initiation of theophylline therapy at a low dose with subsequent slow titration to a predetermined age-related maximum dose will significantly reduce the frequency of these transient adverse effects (see DOSAGE AND ADMINISTRATION). In a small percentage of patients (<3% of children and <10% of adults) the caffeine-like adverse effects persist during maintenance therapy, even at peak serum theophylline concentrations within the therapeutic range (i.e., 10-20 mcg/ml). Dosage reduction may alleviate the caffeine-like adverse effects in these patients, however, persistent adverse effects should result in a reevaluation of the need for continued theophylline therapy and the potential therapeutic benefit of alternative treatment.
Other adverse reactions that have been reported at serum theophylline concentrations <20 mcg/ml include diarrhea, irritability, restlessness, fine skeletal muscle tremors, and transient diuresis. In patients with hypoxia secondary to COPD, multifocal atrial tachycardia and flutter have been reported at serum theophylline concentrations 
15 mcg/ml. There have been a few isolated reports of seizures at serum theophylline concentrations <20 mcg/ml in patients with an underlying neurological disease or in elderly patients. The occurrence of seizures in elderly patients with serum theophylline concentrations <20 mcg/ml may be secondary to decreased protein binding resulting in a larger proportion of the total serum theophylline concentration in the pharmacologically active unbound form. The clinical characteristics of the seizures reported in patients with serum theophylline concentrations <20 mcg/ml have generally been milder than seizures associated with excessive serum theophylline concentrations resulting from an overdose (i.e., they have generally been transient, often stopped without anticonvulsant therapy, and did not result in neurological residua).
General : The chronicity and pattern of theophylline overdosage significantly influences clinical manifestations of toxicity, management and outcome. There are two common presentations: (1) acute overdose , (i.e., ingestion of a single large excessive dose (>10 mg/kg) as occurs in the context of an attempted suicide or isolated medication error) and (2) chronic overdosage , (i.e., ingestion of repeated doses that are excessive for the patient’s rate of theophylline clearance). The most common causes of chronic theophylline overdosage include patient or care giver error in dosing, clinician prescribing of an excessive dose or a normal dose in the presence of factors known to decrease the rate of theophylline clearance, and increasing the dose in response to an exacerbation of symptoms without first measuring the serum theophylline concentration to determine whether a dose increase is safe.
Severe toxicity from theophylline overdose is a relatively rare event. In one health maintenance organization, the frequency of hospital admissions for chronic overdosage of theophylline was about 1 per 1000 person-years exposure. In another study, among 6000 blood samples obtained for measurement of serum theophylline concentration, for any reason, from patients treated in an emergency department, 7% were in the 20-30 mcg/ml range and 3% were >30 mcg/ml. Approximately two-thirds of the patients with serum theophylline concentrations in the 20-30 mcg/ml range had one or more manifestations of toxicity while >90% of patients with serum theophylline concentrations >30 mcg/ml were clinically intoxicated. Similarly, in other reports, serious toxicity from theophylline is seen principally at serum concentrations >30 mcg/ml.
Several studies have described the clinical manifestations of theophylline overdose and attempted to determine the factors that predict life-threatening toxicity. In general, patients who experience an acute overdose are less likely to experience seizures than patients who have experienced a chronic overdosage, unless the peak serum theophylline concentration is >100 mcg/ml. After a chronic overdosage, generalized seizures, life-threatening cardiac arrhythmias, and death may occur at serum theophylline concentrations >30 mcg/ml. The severity of toxicity after chronic overdosage is more strongly correlated with the patient’s age than the peak serum theophylline concentration; patients >60 years are at the greatest risk for severe toxicity and mortality after a chronic overdosage. Pre-existing or concurrent disease may also significantly increase the susceptibility of a patient to a particular toxic manifestation, e.g., patients with neurologic disorders have an increased risk of seizures and patients with cardiac disease have an increased risk of cardiac arrhythmias for a given serum theophylline concentration compared to patients without the underlying disease.
The frequency of various reported manifestations of theophylline overdose according to the mode of overdose are listed in TABLE 4.
Other manifestations of theophylline toxicity include increases in serum calcium, creatine kinase, myoglobin and leukocyte count, decreases in serum phosphate and magnesium, acute myocardial infarction, and urinary retention in men with obstructive uropathy.
Seizures associated with serum theophylline concentrations >30 mcg/ml are often resistant to anticonvulsant therapy and may result in irreversible brain injury if not rapidly controlled. Death from theophylline toxicity is most often secondary to cardiorespiratory arrest and/or hypoxic encephalopathy following prolonged generalized seizures or intractable cardiac arrhythmias causing hemodynamic compromise.
Overdose Management
General Recommendations for Patients with Symptoms of theophylline Overdose or Serum theophylline Concentrations >30 mcg/ml (Note: Serum theophylline concentrations may continue to increase after presentation of the patient for medical care.
1. While simultaneously instituting treatment, contact a regional poison center to obtain updated information and advice on individualizing the recommendations that follow.
2. Institute supportive care, including establishment of intravenous access, maintenance of the airway, and electrocardiographic monitoring.
3. Treatment of Seizures : Because of the high morbidity and mortality associated with theophylline-induced seizures, treatment should be rapid and aggressive. Anticonvulsant therapy should be initiated with an intravenous benzodiazepine, e.g., diazepam, in increments of 0.1-0.2 mg/kg every 1-3 minutes until seizures are terminated. Repetitive seizures should be treated with a loading dose of phenobarbital (20 mg/kg infused over 30-60 minutes). Case reports of theophylline overdose in humans and animal studies suggest that phenytoin is ineffective in terminating theophylline-induced seizures. The doses of benzodiazepines and phenobarbital required to terminate theophylline-induced seizures are close to the doses that may cause severe respiratory depression or respiratory arrest; the clinician should therefore be prepared to provide assisted ventilation. Elderly patients and patients with COPD may be more susceptible to the respiratory depressant effects of anticonvulsants. Barbiturate-induced coma or administration of general anesthesia may be required to terminate repetitive seizures or status epilepticus. General anesthesia should be used with caution in patients with theophylline overdose because fluorinated volatile anesthetics may sensitize the myocardium to endogenous catecholamines released by theophylline. Enflurane appears to less likely to be associated with this effect than halothane and may, therefore, be safer. Neuromuscular blocking agents alone should not be used to terminate seizures since they abolish the musculoskeletal manifestations without terminating seizure activity in the brain.
4. Anticipate Need for Anticonvulsants : In patients with theophylline overdose who are at high risk for theophylline-induced seizures, e.g., patients with acute overdoses and serum theophylline concentrations >100 mcg/ml or chronic overdosage in patients >60 years of age with serum theophylline concentrations >30 mcg/ml, the need for anticonvulsant therapy should be anticipated. A benzodiazepine such as diazepam should be drawn into a syringe and kept at the patient’s bedside and medical personnel qualified to treat seizures should be immediately available. In selected patients at high risk for theophylline-induced seizures, consideration should be given to the administration of prophylactic anticonvulsant therapy. Situations where prophylactic anticonvulsant therapy should be considered in high risk patients include anticipated delays in instituting methods for extracorporeal removal of theophylline (e.g., transfer of a high risk patient from one health care facility to another for extracorporeal removal) and clinical circumstances that significantly interfere with efforts to enhance theophylline clearance (e.g., a neonate where dialysis may not be technically feasible or a patient with vomiting unresponsive to antiemetics who is unable to tolerate multiple-dose oral activated charcoal). In animal studies, prophylactic administration of phenobarbital, but not phenytoin, has been shown to delay the onset of theophylline-induced generalized seizures and to increase the dose of theophylline required to induce seizures (i.e., markedly increases the LD50). Although there are no controlled studies in humans, a loading dose of intravenous phenobarbital (20 mg/kg infused over 60 minutes) may delay or prevent life-threatening seizures in high risk patients while efforts to enhance theophylline clearance are continued. Phenobarbital may cause respiratory depression, particularly in elderly patients and patients with COPD.
5. Treatment of Cardiac Arrhythmias : Sinus tachycardia and simple ventricular premature beats are not harbingers of life-threatening arrhythmias, they do not require treatment in the absence of hemodynamic compromise, and they resolve with declining serum theophylline concentrations. Other arrhythmias, especially those associated with hemodynamic compromise, should be treated with antiarrhythmic therapy appropriate for the type of arrhythmia.
6. Gastrointestinal Decontamination : Oral activated charcoal (0.5 g/kg up to 20 g and repeat at least once 1-2 hours after the first dose) is extremely effective in blocking the absorption of theophylline throughout the gastrointestinal tract, even when administered several hours after ingestion. If the patient is vomiting, the charcoal should be administered through a nasogastric tube or after administration of an antiemetic. Phenothiazine antiemetics such as prochlorperazine or perphenazine should be avoided since they can lower the seizure threshold and frequently cause dystonic reactions. A single dose of sorbitol may be used to promote stooling to facilitate removal of theophylline bound to charcoal from the gastrointestinal tract. Sorbitol, however, should be dosed with caution since it is a potent purgative which can cause profound fluid and electrolyte abnormalities, particularly after multiple doses. Commercially available fixed combinations of liquid charcoal and sorbitol should be avoided in young children and after the first dose in adolescents and adults since they do not allow for individualization of charcoal and sorbitol dosing. Ipecac syrup should be avoided in theophylline overdoses. Although ipecac induces emesis, it does not reduce the absorption of theophylline unless administered within 5 minutes of ingestion and even then is less effective than oral activated charcoal. Moreover, ipecac induced emesis may persist for several hours after a single dose and significantly decrease the retention and the effectiveness of oral activated charcoal.
7. Serum theophylline Concentration Monitoring : The serum theophylline concentration should be measured immediately upon presentation, 2-4 hours later, and then at sufficient intervals, e.g., every 4 hours, to guide treatment decisions and to assess the effectiveness of therapy. Serum theophylline concentrations may continue to increase after presentation of the patient for medical care as a result of continued absorption of theophylline from the gastrointestinal tract. Serial monitoring of serum theophylline serum concentrations should be continued until it is clear that the concentration is no longer rising and has returned to non-toxic levels.
8. General Monitoring Procedures : Electrocardiographic monitoring should be initiated on presentation and continued until the serum theophylline level has returned to a non-toxic level. Serum electrolytes and glucose should be measured on presentation and at appropriate intervals indicated by clinical circumstances. Fluid and electrolyte abnormalities should be promptly corrected. Monitoring and treatment should be continued until the serum concentration decreases below 20 mcg/ml.
9. Enhance Clearance of Theophylline : Multiple-dose oral activated charcoal (e.g., 0.5 mg/kg up to 20 g, every two hours) increases the clearance of theophylline at least twofold by adsorption of theophylline secreted into gastrointestinal fluids. Charcoal must be retained in, and pass through, the gastrointestinal tract to be effective; emesis should therefore be controlled by administration of appropriate antiemetics. Alternatively, the charcoal can be administered continuously through a nasogastric tube in conjunction with appropriate antiemetics. A single dose of sorbitol may be administered with the activated charcoal to promote stooling to facilitate clearance of the adsorbed theophylline from the gastrointestinal tract. Sorbitol alone does not enhance clearance of theophylline and should be dosed with caution to prevent excessive stooling which can result in severe fluid and electrolyte imbalances. Commercially available fixed combinations of liquid charcoal and sorbitol should be avoided in young children and after the first dose in adolescents and adults since they do not allow for individualization of charcoal and sorbitol dosing. In patients with intractable vomiting, extracorporeal methods of theophylline removal should be instituted (see OVERDOSAGE, Extracorporeal Removal).
Specific Recommendations
Acute Overdose :
A. Serum Concentration >20<30 mcg/ml :
1. Administer a single dose of oral activated charcoal.
2. Monitor the patient and obtain a serum theophylline concentration in 2-4 hours to insure that the concentration is not increasing.
B. Serum Concentration >30<100 mcg/ml :
1. Administer multiple dose oral activated charcoal and measures to control emesis.
2. Monitor the patient and obtain serial theophylline concentrations every 2-4 hours to gauge the effectiveness of therapy and to guide further treatment decisions.
3. Institute extracorporeal removal if emesis, seizures, or cardiac arrhythmias cannot be adequately controlled (see OVERDOSAGE, Extracorporeal Removal.)
C. Serum Concentration >100 mcg/ml :
1. Consider prophylactic anticonvulsant therapy.
2. Administer multiple-dose oral activated charcoal and measures to control emesis.
3. Consider extracorporeal removal, even if the patient has not experienced a seizure (see OVERDOSAGE, Extracorporeal Removal.)
4. Monitor the patient and obtain serial theophylline concentrations every 2-4 hours to gauge the effectiveness of therapy and to guide further treatment decisions.
Chronic Overdosage :
1. Administer a single dose of oral activated charcoal.2. Monitor the patient and obtain a serum theophylline concentration in 2-4 hours to insure that the concentration is not increasing.B. Serum Concentration >30 mcg/ml in Patients <60 Years of Age:
1. Administer multiple-dose oral activated charcoal and measures to control emesis.2. Monitor the patient and obtain serial theophylline concentrations every 2-4 hours to gauge the effectiveness of therapy and to guide further treatment decisions.3. Institute extracorporeal removal if emesis, seizures, or cardiac arrhythmias cannot be adequately controlled (see OVERDOSAGE, Extracorporeal Removal.)
C. Serum Concentration >30 mcg/ml in Patients 60 Years of Age:
1. Consider prophylactic anticonvulsant therapy.
2. Administer multiple-dose oral activated charcoal and measures to control emesis.
3. Consider extracorporeal removal even if the patient has not experienced a seizure (see OVERDOSAGE, Extracorporeal Removal).
4. Monitor the patient and obtain serial theophylline concentrations every 2-4 hours to gauge the effectiveness of therapy and to guide further treatment decisions.
Increasing the rate of theophylline clearance by extracorporeal methods may rapidly decrease serum concentrations, but the risks of the procedure must be weighed against the potential benefit. Charcoal hemoperfusion is the most effective method of extracorporeal removal, increasing theophylline clearance up to six fold, but serious complications, including hypotension, hypocalcemia, platelet consumption and bleeding diatheses may occur. Hemodialysis is about as efficient as multiple-dose oral activated charcoal and has a lower risk of serious complications than charcoal hemoperfusion. Hemodialysis should be considered as an alternative when charcoal hemoperfusion is not feasible and multiple-dose oral charcoal is ineffective because of intractable emesis. Serum theophylline concentrations may rebound 5-10 mcg/ml after discontinuation of charcoal hemoperfusion or hemodialysis due to redistribution of theophylline from the tissue compartment. Peritoneal dialysis is ineffective for theophylline removal; exchange transfusions in neonates have been minimally effective.
Immediate Release Oral Products
General Considerations : The steady-state peak serum theophylline concentration is a function of the dose, the dosing interval, and the rate of theophylline absorption and clearance in the individual patient. Because of marked individual differences in the rate of theophylline clearance, the dose required to achieve a peak serum theophylline concentration in the 10-20 mcg/ml range varies fourfold among otherwise similar patients in the absence of factors known to alter theophylline clearance (e.g., 400-1600 mg/day in adults <60 years old and 10-36 mg/kg/day in children 1-9 years old). For a given population there is no single theophylline dose that will provide both safe and effective serum concentrations for all patients. Administration of the median theophylline dose required to achieve a therapeutic serum theophylline concentration in a given population may result in either sub-therapeutic or potentially toxic serum theophylline concentrations in individual patients. For example, at a dose of 900 mg/d in adults <60 years or 22 mg/kg/d in children 1-9 years, the steady-state peak serum theophylline concentration will be <10 mcg/ml in about 30% of patients, 10-20 mcg/ml in about 50% and 20-30 mcg/ml in about 20% of patients. The dose of theophylline must be individualized on the basis of peak serum theophylline concentration measurements in order to achieve a dose that will provide maximum potential benefit with minimal risk of adverse effects.
Transient caffeine-like adverse effects and excessive serum concentrations in slow metabolizers can be avoided in most patients by starting with a sufficiently low dose and slowly increasing the dose, if judged to be clinically indicated , in small increments. Dose increases should only be made if the previous dosage is well tolerated and at intervals of no less than 3 days to allow serum theophylline concentrations to reach the new steady state. Final dosage adjustment should be guided by serum theophylline concentration measurement (see PRECAUTIONS, Laboratory Tests and TABLE 5). Health care providers should instruct patients and care givers to discontinue any dosage that causes adverse effects, to withhold the medication until these symptoms are gone and to then resume therapy at a lower, previously tolerated dosage (see WARNINGS).
If the patient’s symptoms are well controlled, there are no apparent adverse effects, and no intervening factors that might alter dosage requirements (see WARNINGS and PRECAUTIONS), serum theophylline concentrations should be monitored at 6 month intervals for rapidly growing children and at yearly intervals for all others. In acutely ill patients, serum theophylline concentrations should be monitored at frequent intervals, e.g., every 24 hours.
theophylline distributes poorly into body fat, therefore, mg/kg dose should be calculated on the basis of ideal body weight.
The following list contains theophylline dosing titration schema recommended for patients in various age groups and clinical circumstances. TABLE 5 contains recommendations for final theophylline dosage adjustment based on serum theophylline concentrations. Application of these general dosing recommendations to individual patients must take into account the unique clinical characteristics of each patient. In general, these recommendations should serve as the upper limit for dosage adjustments in order to decrease the risk of potentially serious adverse events associated with unexpected large increases in serum theophylline concentration.
A. Infants <1 year old :
1. Initial Dosage :
a. Premature Neonates :
i. <24 days postnatal age; 1.0 mg/kg every 12 hr.
ii. 24 days postnatal age; 1.5 mg/kg every 12 hr.
b. Full Term Infants and Infants Up to 52 Weeks of Age :
- Total daily dose (mg) = [(0.2 × age in weeks)+5.0] × (Kg body Wt).i. up to age 26 weeks; divide dose into 3 equal amounts administered at 8 hour intervals.ii. >26 weeks of age; divide dose into 4 equal amounts administered at 6 hour intervals.
2. Final Dosage : Adjusted to maintain a peak steady-state serum theophylline concentration of 5-10 mcg/ml in neonates and 10-15 mcg/ml in older infants (see TABLE 5) Since the time required to reach steady-state is a function of theophylline half-life, up to 5 days may be required to achieve steady-state in a premature neonate while only 2-3 days may be required in a 6 month old infant without other risk factors for impaired clearance in the absence of a loading dose. If a serum theophylline concentration is obtained before steady-state is achieved, the maintenance dose should not be increased, even if the serum theophylline concentration is < 10 mcg/ml.
B. Children (1-15 years) and Adults (16-60 years) Without Risk Factors for Impaired Clearance :
C. Patients With Risk Factors For Impaired Clearance, The Elderly (>60 Years), And Those In Whom It Is Not Feasible To Monitor Serum theophylline Concentrations : In children 1-15 years of age, the initial theophylline dose should not exceed 16 mg/kg/day up to a maximum of 400 mg/day in the presence of risk factors for reduced theophylline clearance (see WARNINGS) or if it is not feasible to monitor serum theophylline concentrations. In adolescents 16 years and adults, including the elderly, the initial theophylline dose should not exceed 400 mg/day in the presence of risk factors for reduced theophylline clearance (see WARNINGS) or if it is not feasible to monitor serum theophylline concentrations.
D. Loading Dose for Acute Bronchodilatation : An inhaled beta-2 selective agonist, alone or in combination with a systemically administered corticosteroid, is the most effective treatment for acute exacerbations of reversible airways obstruction. theophylline is a relatively weak bronchodilator, is less effective than an inhaled beta-2 selective agonist and provides no added benefit in the treatment of acute bronchospasm. If an inhaled or parenteral beta agonist is not available, a loading dose of an oral immediate release theophylline can be used as a temporary measure. A single 5 mg/kg dose of theophylline, in a patient who has not received any theophylline in the previous 24 hours, will produce an average peak serum theophylline concentration of 10 mcg/ml (range 5-15 mcg/ml). If dosing with theophylline is to be continued beyond the loading dose, the guidelines in Sections A.1.b., B.3, or C., above, should be utilized and serum theophylline concentration monitored at 24 hour intervals to adjust final dosage.
| Peak Serum Concentration | Dosage Adjustment |
|---|---|
| <9.9 mcg/ml | If symptoms are not controlled and current dosage is tolerated, increase dose about 25%. Recheck serum concentration after three days for further dosage adjustment |
| 10 to 14.9 mcg/ml | If symptoms are controlled and current dosage is tolerated, maintain dose and recheck serum concentration at 6-12 month intervals.* If symptoms are not controlled and current dosage is tolerated consider adding additional medication(s) to treatment regimen. |
| 15-19.9 mcg/ml | Consider 10% decrease in dose to provide greater margin of safety even if current dosage is tolerated.* |
| 20-24.9 mcg/ml | Decrease dose by 25% even if no adverse effects are present. Recheck serum concentration after 3 days to guide further dosage adjustment. |
| 25-30 mcg/ml | Skip next dose and decrease subsequent doses at least 25% even if no adverse effects are present. Recheck serum concentration after 3 days to guide further dosage adjustment. If symptomatic, consider whether overdose treatment is indicated (see recommendations for chronic overdosage). If theophylline is subsequently resumed, decrease dose by at least 50% and recheck serum concentration after 3 days to guide further dosage adjustment. |
| * Dose reduction and/or serum theophylline concentration measurement is indicated whenever adverse effects are present, physiologic abnormalities that can reduce theophylline clearance occur (e.g., sustained fever), or a drug that interacts with theophylline is added or discontinued (see WARNINGS). | |
Theo-Dur Sprinkle may be administered by carefully opening the capsule and sprinkling the beaded contents on a spoonful of soft food such as applesauce or pudding. The soft food should be swallowed immediately without chewing and followed with a glass of cool water or juice to ensure complete swallowing of the beads. It is recommended that the food used should not be hot and should be soft enough to be swallowed without chewing. Any bead/food mixture should be used immediately and not stored for future use. The small amount of food (one spoonful) used to administer the dose will not alter the bioavailability of Theo-Dur Sprinkle; however, the dosing should be at least 1 hour before or 2 hours after a meal. SUBDIVIDING THE CONTENTS OF A CAPSULE IS NOT RECOMMENDED.
Dosage Guidelines
Because administration of Theo-Dur Sprinkle at the time of food ingestion has been shown to result in significantly lower peak-serum concentrations and reduced extent of absorption (bioavailability). patients should be instructed to take this medication at least 1 hour before or 2 hours after a meal (see DRUG INTERACTIONS).
Taking Theo-Dur Sprinkle at 12-hour intervals under the above restrictive recommendations in regard to food ingestion may be difficult for the patient to follow. Under such circumstances, consideration should be given to prescribing this drug every 8 hours (giving one-third of the 24-hour dosage requirement with each dose), if this regimen would more easily permit dosing under fasting conditions.
I. Acute Symptoms: NOTE: Status asthmaticus should be considered a medical emergency and is defined as that degree of bronchospasm which is not rapidly responsive to usual doses of conventional bronchodilators. Optimal therapy for such patients frequently requires both additional medication, Parenterally administered, and close monitoring , preferably in an intensive care setting. Theo-Dur Sprinkle is not intended for patients experiencing an acute episode of bronchospasm (associated with asthma, chronic bronchitis, or emphysema). Such patients require rapid relief of symptoms and should be treated with an immediate release or intravenous theophylline preparation (or other bronchodilators) and not with controlled-release products.
A. Initiating Therapy with an Immediate-Release Product: It is recommended that the appropriate dosage be established sing an immediate-release preparation. Children weighing less than 25 kg should have their daily dosage requirements established with a liquid preparation to permit small dosage increments. Slow clinical titration is generally preferred to help assure acceptance and safety of the medication, and to allow the patient to develop tolerance to transient caffeine-like side effects. Then, if the total 24-hour dose can be given by use of the sustained-release product, the patient can usually be switched to Theo-Dur Sprinkle, giving one-half of the daily dose at 12-hour intervals. Patients who metabolize theophylline rapidly such as the young, smokers, and some nonsmoking adults, are the most likely candidates for dosing at 8-hour intervals. Such patients can generally be identified as having trough-serum concentrations lower than desired for repeatedly exhibiting symptoms near the end of a dosing interval.
B. Initiating Therapy with Theo-Dur Sprinkle: Alternatively, therapy can be initiated with Theo-Dur Sprinkle since it is available in dosage strengths which permit titration and adjustments of dosage in adults and older children: Initial Dose: 16 mg/kg/24 hours or 400 mg/24 hours (whichever is less) of anhydrous theophylline in 2 divided doses, 12-hour intervals. Increasing Dose: The above dosage may be increased in approximately 25% increments at 3-day intervals so long as the drug is tolerated; until clinical response is satisfactory or the maximum dose as indicated in Section III (below) is reached. The serum concentration may be checked at these intervals, but at a minimum, should be checked at the end of this adjustment period.
II. Maintenance Dose of theophylline where the Serum Concentration is not Measured: See TABLE 5.
WARNING : DO NOT ATTEMPT TO MAINTAIN ANY DOSE THAT IS NOT TOLERATED
IV. Measurement of Serum theophylline Concentrations During Chronic Therapy: If the above maximum doses are to maintained or exceeded, serum theophylline measurement is recommended. The serum sample should be obtained at the time of peak absorption: 1 to 2 hours after administration for immediate-release products and 5 to 10 hours after dosing for Theo-Dur Sprinkle. It is important that the patient will have missed no doses during the previous 48 hours and the dosing intervals will have been reasonably typical with no added doses during that time. DOSAGE ADJUSTMENT BASED ON SERUM theophylline CONCENTRATION MEASUREMENTS WHEN THESE INSTRUCTIONS HAVE NOT BEEN FOLLOWED MAY RESULT IN RECOMMENDATIONS THAT PRESENT RISK OF TOXICITY TO THE PATIENT.
V. Final Adjustment of Dosage: Caution should be exercised for younger children who cannot complain of minor side effects. Those with cor pulmonale, congestive heart failure, and/or other liver disease may have unusually low dosage requirements and thus may experience toxicity at the maximum dose recommended above. It is important that no patient be maintained on any dosage that is not tolerated. In instructing patients to increase dosage according to the schedule above, they should be instructed not to take a subsequent dose if apparent side effects occur and to resume therapy at a lower dose once adverse effects have disappeared.
TABLE 7 Sustained-Release Capsules
Dosage Adjustment after serum theophylline measurement.
| If Serum theophylline is: | Directions | |
|---|---|---|
| Within normal limits | 10-20 mcg/ml | Maintain dosage of tolerated. Recheck serum theophylline concentration at 6- to 12-month intervals.* |
| Too High | 20-25 mcg/ml | Decrease doses by about 10%. Serum theophylline concentrations should be checked until within normal limits. Recheck at 6 to 12 months. |
| 25-30 mcg/ml | Skip next dose and decrease subsequent doses by about 25%. Serum theophylline concentrations should be checked until within normal limits. Recheck at 6 to 12 months. | |
| over 30 mcg/ml | Skip next 2 doses and decrease subsequent doses by 50%. Serum theophylline should be checked until within normal limits. Recheck at 6 to 12 months. | |
| Too Low | 7.5-10 mcg/ml | Increase dose by about 25%.** Serum theophylline concentrations should be checked for guidance in further dosage adjustment. Recheck serum theophylline concentration at 6- to 12-month intervals.* |
| 5-7.5 | Increase dose by about 25% to the nearest dose increment and recheck serum theophylline for guidance in further dosage adjustment (another increase will probably be needed, but provides a safety check). | |
| * Finer adjustments in dosage may be needed for some patients. | ||
| ** The total daily dose may need to be administered at more frequent intervals if asthma symptoms occur repeatedly at the end of a dosing interval. | ||