ACCOLATE ACCOLATE® ( zafirlukast ) TABLETS DESCRIPTION Zafirlukast is a synthetic, selective peptide leukotriene receptor antagonist (LTRA), with the chemical name 4-(5-cyclopentyloxy-carbonylamino-1-methyl-indol-3-ylmethyl)-3-methoxy-N-o- tolylsulfonylbenzamide. The molecular weight of zafirlukast is 575.7 and the structural formula is: The empirical formula is: C 31 H 33 N 3 O 6 S Zafirlukast, a fine white to pale yellow amorphous powder, is practically insoluble in water. It is slightly soluble in methanol and freely soluble in tetrahydrofuran, dimethylsulfoxide, and acetone. ACCOLATE is supplied as 10 and 20 mg tablets for oral administration. Inactive Ingredients: Film-coated tablets containing croscarmellose sodium, lactose, magnesium stearate, microcrystalline cellulose, povidone, hypromellose, and titanium dioxide. CLINICAL PHARMACOLOGY Mechanism of Action: Zafirlukast is a selective and competitive receptor antagonist of leukotriene D 4 and E 4 (LTD 4 and LTE 4 ), components of slow-reacting substance of anaphylaxis (SRSA). Cysteinyl leukotriene production and receptor occupation have been correlated with the pathophysiology of asthma, including airway edema, smooth muscle constriction, and altered cellular activity associated with the inflammatory process, which contribute to the signs and symptoms of asthma. Patients with asthma were found in one study to be 25- 100 times more sensitive to the bronchoconstricting activity of inhaled LTD 4 than nonasthmatic subjects. In vitro studies demonstrated that zafirlukast antagonized the contractile activity of three leukotrienes (LTC 4 , LTD 4 and LTE 4 ) in conducting airway smooth muscle from laboratory animals and humans. Zafirlukast prevented intradermal LTD 4 -induced increases in cutaneous vascular permeability and inhibited inhaled LTD 4 -induced influx of eosinophils into animal lungs. Inhalational challenge studies in sensitized sheep showed that zafirlukast suppressed the airway responses to antigen; this included both the early- and late-phase response and the nonspecific hyperresponsiveness. In humans, zafirlukast inhibited bronchoconstriction caused by several kinds of inhalational challenges. Pretreatment with single oral doses of zafirlukast inhibited the bronchoconstriction caused by sulfur dioxide and cold air in patients with asthma. Pretreatment with single doses of zafirlukast attenuated the early- and late-phase reaction caused by inhalation of various antigens such as grass, cat dander, ragweed, and mixed antigens in patients with asthma. Zafirlukast also attenuated the increase in bronchial hyperresponsiveness to inhaled histamine that followed inhaled allergen challenge. Clinical Pharmacokinetics and Bioavailability: Absorption Zafirlukast is rapidly absorbed following oral administration. Peak plasma concentrations are generally achieved 3 hours after oral administration. The absolute bioavailability of zafirlukast is unknown. In two separate studies, one using a high fat and the other a high protein meal, administration of zafirlukast with food reduced the mean bioavailability by approximately 40%. Distribution Zafirlukast is more than 99% bound to plasma proteins, predominantly albumin. The degree of binding was independent of concentration in the clinically relevant range. The apparent steady-state volume of distribution (Vss/F) is approximately 70 L, suggesting moderate distribution into tissues. Studies in rats using radiolabeled zafirlukast indicate minimal distribution across the blood-brain barrier. Metabolism Zafirlukast is extensively metabolized. The most common metabolic products are hydroxylated metabolites which are excreted in the feces. The metabolites of zafirlukast identified in plasma are at least 90 times less potent as LTD 4 receptor antagonists than zafirlukast in a standard in vitro test of activity. In vitro studies using human liver microsomes showed that the hydroxylated metabolites of zafirlukast excreted in the feces are formed through the cytochrome P450 2C9 (CYP2C9) pathway. Additional in vitro studies utilizing human liver microsomes show that zafirlukast inhibits the cytochrome P450 CYP3A4 and CYP2C9 isoenzymes at concentrations close to the clinically achieved total plasma concentrations (see Drug Interactions ). Excretion The apparent oral clearance (CL/f) of zafirlukast is approximately 20 L/h. Studies in the rat and dog suggest that biliary excretion is the primary route of excretion. Following oral administration of radiolabeled zafirlukast to volunteers, urinary excretion accounts for approximately 10% of the dose and the remainder is excreted in feces. Zafirlukast is not detected in urine. In the pivotal bioequivalence study, the mean terminal half-life of zafirlukast is approximately 10 hours in both normal adult subjects and patients with asthma. In other studies, the mean plasma half-life of zafirlukast ranged from approximately 8 to 16 hours in both normal subjects and patients with asthma. The pharmacokinetics of zafirlukast are approximately linear over the range from 5 mg to 80 mg. Steady-
INDICATIONS AND USAGE
ACCOLATE is indicated for the prophylaxis and chronic treatment of asthma in adults and children 5 years of age and older.
ACCOLATE is contraindicated in patients who are hypersensitive to zafirlukast or any of its inactive ingredients.
ACCOLATE is contraindicated in patients with hepatic impairment including hepatic cirrhosis.
DOSAGE AND ADMINISTRATION
Because food can reduce the bioavailability of zafirlukast, ACCOLATE should be taken at least 1 hour before or 2 hours after meals.
Adults and Children 12 years of age and older
The recommended dose of ACCOLATE in adults and children 12 years and older is 20 mg twice daily.
Pediatric Patients 5 through 11 years of age
The recommended dose of ACCOLATE in children 5 through 11 years of age is 10 mg twice daily.
Based on cross-study comparisons, the clearance of zafirlukast is reduced in elderly patients (65 years of age and older), such that Cmax and AUC are approximately twice those of younger adults. In clinical trials, a dose of 20 mg twice daily was not associated with an increase in the overall incidence of adverse events or withdrawals because of adverse events in elderly patients.