Montelukast is a specific cysteinyl leukotriene receptor antagonist, belonging to the quinoline series and therapeutic agent used for the treatment of bronchial asthma and allergic rhinitis. This review described the impurities, toxicity studies, adverse effects of drug montelukast. The presence of impurities affect the efficacy and safety of pharmaceutical products. Sulfoxide impurity was found to be having a major effect on efficacy. The common adverse effects found were headache, upper respiratory infection and Neuropsychiatric Events, which were not much different compared to placebo. Toxicities of montelukast impurities have to be carefully improved because it is chronically used in patients, particularly children. These studies implied its effectiveness and tolerance in children. It also has been associated with Churg-Strauss syndrome in a small number of adults. We have studied comparative action and side effects of Montelukast with other drugs along with some drug-drug interaction studies. The relation between neuropsychiatric events and montelukast's use is clarified in this review. Major concerns of montelukast-associated adverse drug reactions included the Churg-Strauss syndrome. This drug has some inhibitory effect on Cytochrome enzymes required in drug metabolism. In drug-interaction studies, the recommended dose of montelukast with effect on pharmacokinetics of various drugs are discussed. Our findings suggested that the toxicity of drug impurities can be monitored by measuring its level, safety profile and under good supervision.
