Patients should be advised never to use oral Montelukast to treat acute asthma attacks and to keep their usual appropriate rescue medication for this purpose readily available. If an acute attack occurs, a short-acting inhaled β-agonist should be used. Patients should seek their doctor's advice as soon as possible if they need more inhalations of short-acting β-agonists than usual. Montelukast should not be substituted for inhaled or oral corticosteroids. Although drowsiness is rare, it can occur and may affect the performance of skilled tasks. Occasional reports of convulsions in patients taking antihistamines suggest a need for caution in patients with epilepsy. Many antihistamines are excreted in the urine in the form of active metabolites so that dosage reduction may be necessary in renal impairment. As for the non-sedating antihistamines in general, reduced dosage is recommended for patients with hepatic or renal impairment.