THEOPHYLLINE

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. Theophylline Oral Solution, USP is available as a clear red color liquid with a fruit flavor intended for oral administration, containing 80 mg of theophylline anhydrous in each 15 mL (tablespoonful). Theophylline Oral Solution, USP also contains the following inactive ingredients: citric acid, sodium saccharin, sodium benzoate, glycerin, propylene glycol, FD&C Red #40, natural and artificial fruity flavor and purified water. Theophylline Oral Solution, USP has a pH of 4.3 - 4.7 image description

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.

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 to 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).* 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 x age in weeks)+5.0] x (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 TableVI ). 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. Titration Step Children < 45 Kg Children > 45 Kg and Adults 1. Starting Dosage 12-14 mg/kg/day up to a maximum of 300 mg/day divided Q4-6 hrs* 300 mg/day divided Q6-8 hrs* 2. After 3 days, if tolerated, increase dose to: 16 mg/kg/day up to a maximum of 400 mg/day divided Q4-6 hrs* 400 mg/day divided Q6-8 hrs* 3. After 3 more days, if tolerated dose to: 20 mg/kg/day increase up to a maximum of 600 mg/day divided Q4-6 hrs* 600 mg/day divided Q6-8 hrs* 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. 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. * 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. Table VI. Dosage adjustment guided by serum theophylline concentration. 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 - 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. 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 ).

Theophylline Oral Solution is contraindicated in patients with a history of hypersensitivity to theophylline or other components in the product.

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 , Table V). 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). Table IV. Manifestations of theophylline toxicity.* Percentage of patients reported with sign or symptom Acute Overdose (Large Single Dose) Chronic Overdosage (Multiple Excessive Doses) Sign/Symptom Study 1 (n=157) Study 2 (n=14) Study 1 (n=92) Study 2 (n=102) Asymptomatic NR ** 0 NR ** 6 Gastrointestinal Vomiting 73 93 30 61 Abdominal Pain NR ** 21 NR ** 12 Diarrhea NR ** 0 NR ** 14 Hematemesis NR ** 0 NR ** 2 Metabolic/Other Hypokalemia 85 79 44 43 Hyperglycemia 98 NR ** 18 NR ** Acid/base disturbance 34 21 9 5 Rhabdomyolysis NR ** 7 NR ** 0 Cardiovascular Sinus tachycardia 100 86 100 62 Other supraventricular tachycardias 2 21 12 14 Ventricular premature beats 3 21 10 19 Atrial fibrillation or flutter 1 NR ** 12 NR ** Multifocal atrial tachycardia 0 NR ** 2 NR ** Ventricular arrhythmias with hemodynamic instability 7 14 40 0 Hypotension/shock NR ** 21 NR ** 8 Neurologic Nervousness NR ** 64 NR ** 21 Tremors 38 29 16 14 Disorientation NR ** 7 NR ** 11 Seizures 5 14 14 5 Death 3 21 10 4 * These data are derived from two studies in patients with serum theophylline concentrations >30 mcg/mL. In the first study (Study #1 - Shanon, Ann Intern Med 1993;119:1161-67), data were prospectively collected from 249 consecutive cases of theophylline toxicity referred to a regional poison center for consultation. In the second study (Study #2 - Sessler, Am J Med 1990;88:567-76), data were retrospectively collected from 116 cases with serum theophylline concentrations >30 mcg/mL among 6000 blood samples obtained for measurement of serum theophylline concentrations in three emergency departments. Differences in the incidence of manifestations of theophylline toxicity between the two studies may reflect sample selection as a result of study design (e.g., in Study #1, 48% of the patients had acute intoxications versus only 10% in Study #2) and different methods of reporting results. ** NR = Not reported in a comparable manner