Since montelukast and its metabolites are not renally eliminated, renal impairment should have no effect on the pharmacokinetics. Montelukast is contraindicated in patients with hypersensitivity to the drug or any of the inactive ingredients. Montelukast is not indicated for the reversal of bronchospasm in acute asthma and should not be used to treat acute episodes of asthma, but it may be continued during acute exacerbations of asthma. It should not be used as monotherapy in patients with exercise-induced bronchospasm. No teratogenicity was observed in animal studies.
Animal studies indicate montelukast is excreted in breast milk.
Therefore, it should be administered with caution in nursing mothers. The safety and efficacy of montelukast in children under 6 years of age have not been demonstrated. The most common side effects in clinical trials occurring at a greater frequency than with placebo included headache, respiratory infections, dyspepsia, abdominal pain and rash. Hepatic transaminase elevations have been reported during montelukast therapy, but not at an incidence greater than observed with placebo. Unlike zafirlukast, montelukast does not inhibit any of the cytochrome P450 isoenzymes.