DailyMed Label: Theophylline, anhydrous

DailyMed Label: Theophylline, anhydrous

2006

DailyMed Prescription

Theophylline, anhydrous

Theophylline, anhydrous

Inwood Laboratories, Inc.

NDC: 0258-3638

NDC: 0258-3634

NDC: 0258-3625

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-, and is represented by the following structural formula: The molecular formula of anhydrous theophylline is C 7 H 8 N 4 O 2 with a molecular weight of 180.17. Each extended-release capsule, for oral administration, contains 125 mg, 200 mg, or 300 mg anhydrous theophylline in the form of long-acting beads within a dye-free hard gelatin capsule. In addition, each capsule contains the following inactive ingredients: black iron oxide, butylparaben, castor oil, edetate calcium disodium, ethylcellulose, gelatin, methylparaben, pharmaceutical glaze, povidone, propylparaben, sodium lauryl sulfate, sodium propionate, starch, sugar spheres, and talc. The 200 mg, and 300 mg capsules also contain titanium dioxide. This extended-release capsule formulation can be administered with a 12-hour dosing interval for a majority of patients and a 24-hour dosing interval for selected patients (see DOSAGE AND ADMINISTRATION ). These capsules comply with USP Drug Release Test 10.

Theophylline Extended-release capsules are 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.

Taking Theophylline Extended-release Capsules immediately after a high-fat content meal may alter its rate of absorption (see CLINICAL PHARMACOLOGY and PRECAUTIONS, Drug-Food Interactions ). However, the differences are usually small and Theophylline Extended-release Capsules may normally be administered without regard to meals. 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 (See Table V ). 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. Dosage adjustment should be guided by serum theophylline concentration measurement (see PRECAUTIONS, Laboratory Tests and DOSAGE AND ADMINISTRATION, Table VI ). 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. Table V contains theophylline dosing titration schema recommended for patients in various age groups and clinical circumstances. Table VI contains recommendations for theophylline dosage adjustment based upon 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. Table V. Dosing initiation and titration (as anhydrous theophylline) * * Patients with more rapid metabolism, clinically identified by higher than average dose requirements, should receive a smaller dose more frequently to prevent breakthrough symptoms resulting from low trough concentrations before the next dose. A reliably absorbed slow-release formulation will decrease fluctuations and permit longer dosing intervals. A.    Children (1-15 years) and adults (16-60 years) without risk factors for impaired clearance. Titration Step Children < 45 kg Children > 45 kg and adults 1 Starting Dosage 12-14 mg/kg/day up to a maximum 300 mg/day divided of 300 mg/day divided Q8-12 hrs* Q8-12 hrs* 2 After 3 days, 16 mg/kg/day up to a maximum 400 mg/day divided if tolerated , of 400 mg/day divided Q8-12 hrs* Q8- 12 hrs* increase dose to: 3 After 3 more days, if 20 mg/kg/day up to a maximum 600 mg/day divided tolerated and if needed, of 600 mg/day divided Q8-12 hrs* Q8-12 hrs* increase dose to: B. Once-Daily Dosing : The slow absorption rate of this preparation may allow once-daily administration in adult nonsmokers with appropriate total body clearance and other patients with low dosage requirements. Once-daily dosing should be considered only after the patient has been gradually and satisfactorily treated to therapeutic levels with q12h dosing. Once-daily dosing should be based on the dosing guidelines in Table V and Table VI , and should be initiated at the end of the last q12h dosing interval. The trough concentration (C min ) obtained following conversion to once-daily dosing may be lower (especially in high clearance patients) and the peak concentration (C max ) may be higher (especially in low clearance patients) than that obtained with q12h dosing. If symptoms recur, or signs of toxicity appear during the once-daily dosing interval, dosing on the q12h basis should be reinstituted. It is essential that serum theophylline concentrations be monitored before and after transfer to once-daily dosing. Food and posture, along with changes associated with circadian rhythm, may influence the rate of absorption and/or clearance rates of theophylline from extended-release dosage forms administered at night. The exact relationship of these and other factors to nighttime serum concentrations and the clinical significance of such findings require additional study. Therefore, it is not recommended that Theophylline Extended-release Capsules when used as a once-a-day product, be administered at night. 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 final 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 final 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. Table VI. Dosage adjustment guided by serum theophylline concentration. Peak Serum Concentration 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 ). <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 ). >30 mcg/mL Treat overdose as 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. Theophylline Extended-release Capsules 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. SUBDIVIDING THE CONTENTS OF A CAPSULE IS NOT RECOMMENDED.

Theophylline Extended - release capsules is contraindicated in patients with a history of hypersensitivity to theophylline or other components in the product.

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, Table V ). 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: When initiating therapy to guide final dosage adjustment after titration. Before making a dose increase to determine whether the serum concentration is sub-therapeutic in a patient who continues to be symptomatic. Whenever signs or symptoms of theophylline toxicity are present. 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 II 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 (expected peak concentration at steady state: 13.7±1.9 μg/mL after 600 or 900 mg of Theophylline Extended-release Capsules per day for six days with q24h dosing). 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. Trough concentrations at steady state are expected to occur at the end of a 12h dosing interval prior to the next dose (q12h dosing) or at the end of a 24h dosing interval prior to the next dose (q24h dosing). 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. 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 μεq/l to 800 μεq/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. The patient (or parent/care giver) should be instructed to seek medical advice whenever nausea, vomiting, persistent headache, insomnia or 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. When prescribing administration by the sprinkle method, details of the proper technique should be explained to the patient. 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 II have the potential to produce clinically significant pharmacodynamic or pharmacokinetic interactions with theophylline. The information in the “Effect” column of Table II 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 drugs listed in Table III have either been documented not to interact with theophylline or do not produce a clinically significant interaction (i.e., <15% change in theophylline clearance). The listing of drugs in Tables II and III are current as of February 9, 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 II . 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. Table II. Clinically significant drug interactions with theophylline * . * Refer to PRECAUTIONS, 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 ** 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 decrease 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. Similar to cimetidine. Halothane Halothane sensitizes the myocardium. to catecholamines, theophylline increases release of endogenous catecholamines. Increased risk of ventricular arrhythmias. Interferon, human recombinant alpha-A Decreases theophylline clearance. 100% increase Isoproterenol (IV) Increases theophylline clearance. 20% decrease Ketamine Pharmacologic seizure threshold. May lower theophylline 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. 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. Decreases renal clearance of theophylline. 20% decrease 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 Table III. Drugs that have been documented not to interact with theophylline or drugs that produce no clinically significant interaction with theophylline.* * Refer to PRECAUTIONS, Drug Interactions for information regarding table. albuterol, diltiazem medroxyprogesterone roxithromycin    systemic and inhaled dirithromycin methylprednisolone sorbitol amoxicillin enflurane metronidazole    (purgative doses ampicillin, famotidine metoprolol    do not inhibit    with or without felodipine nadolol    theophylline    sulbactam finasteride nifedipine    absorption) atenolol hydrocortisone nizatidine sucralfate azithromycin isoflurane norfloxacin terbutaline, systemic caffeine, isoniazid ofloxacin terfenadine    dietary ingestion isradipine omeprazole tetracycline cefaclor influenza vaccine prednisone, tocainide co-trimoxazole ketoconazole    prednisolone    (trimethoprim and lomefloxacin ranitidine    sulfamethoxazole) mebendazole rifabutin 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. Drug-Food: Taking Theophylline Extended-release Capsules immediately after a high-fat content meal such as 8 ounces whole milk, one fried egg, one slice of Canadian bacon, one English muffin with butter, 4 ounces hash brown potatoes, one slice of American cheese (about 240 calories, including approximately 27 g of fat) may result in an increase in the C max , but with no significant difference in the extent of absorption (see CLINICAL PHARMACOLOGY ). The influence of the type and amount of other foods, as well as the time interval between drug and food, has not been studied. 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 B6C3F 1 mice at oral doses of 120, 270 and 500 mg/kg (approximately 1.0- 3.0 times the human dose on a mg/m 2 basis) impaired fertility, as evidenced by decreases in the number of live pups per litter, decreases in the mean number 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 B6C3F 1 mice at oral doses of 40-300 mg/kg (approximately 2.0 times the human dose on a mg/m 2 basis). At the high dose, systemic toxicity was observed in both species including decreases in testicular weight. CATEGORY C : 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/m 2 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/m 2 basis. At a dose of 220 mg/kg, embryotoxicity was observed in rats in the absence of maternal toxicity. 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. 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 I, WARNINGS, and DOSAGE AND ADMINISTRATION, Table V ). 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.

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

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 II have the potential to produce clinically significant pharmacodynamic or pharmacokinetic interactions with theophylline. The information in the “Effect” column of Table II 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 drugs listed in Table III have either been documented not to interact with theophylline or do not produce a clinically significant interaction (i.e., <15% change in theophylline clearance). The listing of drugs in Tables II and III are current as of February 9, 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 II . 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. Table II. Clinically significant drug interactions with theophylline * . * Refer to PRECAUTIONS, 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 ** 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 decrease 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. Similar to cimetidine. Halothane Halothane sensitizes the myocardium. to catecholamines, theophylline increases release of endogenous catecholamines. Increased risk of ventricular arrhythmias. Interferon, human recombinant alpha-A Decreases theophylline clearance. 100% increase Isoproterenol (IV) Increases theophylline clearance. 20% decrease Ketamine Pharmacologic seizure threshold. May lower theophylline 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. 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. Decreases renal clearance of theophylline. 20% decrease 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 Table III. Drugs that have been documented not to interact with theophylline or drugs that produce no clinically significant interaction with theophylline.* * Refer to PRECAUTIONS, Drug Interactions for information regarding table. albuterol, diltiazem medroxyprogesterone roxithromycin    systemic and inhaled dirithromycin methylprednisolone sorbitol amoxicillin enflurane metronidazole    (purgative doses ampicillin, famotidine metoprolol    do not inhibit    with or without felodipine nadolol    theophylline    sulbactam finasteride nifedipine    absorption) atenolol hydrocortisone nizatidine sucralfate azithromycin isoflurane norfloxacin terbutaline, systemic caffeine, isoniazid ofloxacin terfenadine    dietary ingestion isradipine omeprazole tetracycline cefaclor influenza vaccine prednisone, tocainide co-trimoxazole ketoconazole    prednisolone    (trimethoprim and lomefloxacin ranitidine    sulfamethoxazole) mebendazole rifabutin 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. Drug-Food: Taking Theophylline Extended-release Capsules immediately after a high-fat content meal such as 8 ounces whole milk, one fried egg, one slice of Canadian bacon, one English muffin with butter, 4 ounces hash brown potatoes, one slice of American cheese (about 240 calories, including approximately 27 g of fat) may result in an increase in the C max , but with no significant difference in the extent of absorption (see CLINICAL PHARMACOLOGY ). The influence of the type and amount of other foods, as well as the time interval between drug and food, has not been studied.

Theophylline Extended-release Capsules USP are available as 125 mg, 200 mg, or 300 mg and have the following identification characteristics: Theophylline Extended-release 125 mg clear/clear capsule, with off-white seeds, and imprint: IL/3638. Available in bottles of 100 (NDC 0258-3638-01). Theophylline Extended-release 200 mg clear/opaque white capsule, with off-white seeds, and imprint: IL/3634. Available in bottles of 100 (NDC 0258-3634-01). Theophylline Extended-release 300 mg opaque white/clear capsule, with off-white seeds, and imprint: IL/3625. Available in bottles of 100 (NDC 0258-3625-01). STORAGE: Store at controlled room temperature 15° - 30°C (59°- 86°F). Dispense in a tight container as defined in the USP. Keep this and all medications out of the reach of children. Inwood Laboratories, Inc. Subsidiary of FOREST LABORATORIES, INC. Inwood, New York 11096 MG #9933 (06) Rev. 03/05

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 bronchodilation 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. 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. 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 I ) and co-administration of other drugs (see Table II ) 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 ). Table I. Mean and range of total body clearance and half-life of theophylline related to age and altered physiological states.¶ Total body clearance* Half-life mean (range)†† mean (range)†† Population characteristics       (mL/kg/min)       (hr) ¶ For various North American patient populations from literature reports. Different rates of elimination and consequent dosage requirements have been observed among other peoples. * Clearance represents the volume of blood completely cleared of theophylline by the liver in one minute. Values listed were generally determined at serum theophylline concentrations <20 mcg/mL; clearance may decrease and half-life may increase at higher serum concentrations due to non-linear pharmacokinetics. †† Reported range or estimated range (mean ± 2 SD) where actual range not reported. † NR = not reported or not reported in a comparable format. ** Median Age Premature neonates    postnatal age 3-15 days 0.29 (0.09-0.49) 30 (17-43)    postnatal age 25-57 days 0.64 (0.04-1.2) 20 (9.4-30.6) Term infants    postnatal age 1-2 days NR† 25.7 (25-26.5)    postnatal age 3-30 weeks NR† 11 (6-29) Children    1-4 years 1.7 (0.5-2.9) 3.4 (1.2-5.6)    4-12 years 1.6 (0.8-2.4) NR†    13-15 years 0.9 (0.48-1.3) NR†    16-17 years 1.4 (0.2-2.6) 3.7 (1.5-5.9) Adults (16-60 years)    otherwise healthy    non-smoking asthmatics 0.65 (0.27-1.03) 8.7 (6.1-12.8) Elderly (>60 years)    non-smokers with normal cardiac,    liver, and renal function 0.41 (0.21-0.61) 9.8 (1.6-18) Concurrent illness or altered physiological state Acute pulmonary edema 0.33** (0.07-2.45) 19** (3.1-82) COPD->60 years, stable    non-smoker >1 year 0.54 (0.44-0.64) 11 (9.4-12.6) COPD with cor pulmonale 0.48 (0.08-0.88) NR† Cystic fibrosis (14-28 years) 1.25 (0.31-2.2) 6.0 (1.8-10.2) Fever associated viral respiratory    illness (children with    acute 9-15 years) NR† 7.0 (1.0-13) Liver disease - cirrhosis 0.31** (0.1-0.7) 32** (10-56)          acute hepatitis 0.35 (0.25-0.45) 19.2 (16.6-21.8)          cholestasis 0.65 (0.25-1.45) 14.4 (5.7-31.8) Pregnancy - 1st trimester NR† 8.5 (3.1-13.9)                   2nd trimester NR† 8.8 (3.8-13.8)                   3rd trimester NR† 13.0 (8.4-17.6) Sepsis with multi-organ failure 0.47 (0.19-1.9) 18.8 (6.3-24.1) Thyroid disease - hypothyroid 0.38 (0.13-0.57) 11.6 (8.2-25)                           hyperthyroid 0.8 (0.68-0.97) 4.5 (3.7-5.6) 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 immediate-release theophylline 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. In a single-dose bioavailability study in 20 normal subjects, Theophylline Extended-release Capsules 300 mg produced mean peak plasma concentrations of 3.8 ± 0.9 μg/mL at a mean time of 6.3 ± 2.0 hours after dosing. The AUC 0-72 was 86.4 ± 23.3 μg hr/mL. Subjects fasted overnight before dosing and four hours after the dose. At steady state in a multiple-dose bioavailability study in 19 normal subjects with q12h dosing (600 mg/day) for six days, the mean C max and C min were 9.5 ± 1.9 and 7.0 ± 1.6 μg/mL, respectively. The mean percent fluctuation [(C max - Cmin/Cmin) x 100] was 36.9 ± 14.1%. Subjects fasted 10 hours before the dose and 4 hours after the dose was administered on the days that the blood samples were drawn. Taking Theophylline Extended-release Capsules 300 mg immediately after a high-fat content meal may result in an increase in the C max but with no significant difference in the extent of absorption (AUC). In a single-dose bioavailability study, 15 normal nonsmoking adults were given 300 mg extended-release theophylline with food and under fasting conditions. Results (mean ± S.D.): Food Fasting AUC 0-72 (μg hr/mL) 153.0 ± 51.9 149.7 ± 39.5 C max (μg/mL) 8.4 ± 1.8 6.9 ± 1.31 T max (hr) 7.3 ± 1.7 7.1 ± 1.3 Steady-state pharmacokinetics were also determined in 21 normal male volunteers who received 600 or 900 mg of theophylline per day for six days. Subjects fasted overnight before dosing and four hours after the dose. At steady state with q24h dosing, the mean C max and C min were 13.7 ± 1.9 and 5.2 ± 1.2 μg/mL, respectively. The mean percent fluctuation [(C max - C min /C min )x 100] was 172.8 ± 64%. Theophylline Extended-release Capsules were studied following a single dose administration of 300 mg by sprinkling the contents of the capsule over a small amount of applesauce. This study demonstrated that the bioavailability (AUC 76.8 + 16.4 μg hr/mL and C max 3.5 ± 0.5 μg/mL) of Theophylline Extended-release Capsules 300 mg following this means of administration was comparable to administration under fasting conditions. 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 DOSAGE AND ADMINISTRATION, Table VI ). 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. (See Table I 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 ). 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.

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.