Contains lactose. May affect ability to drive & use machines. Moderate to severe renal impairment (CrCl <79 to >10 mL/min). Pregnancy & lactation. Montelukast: Never use to treat acute asthma attacks & keep usual appropriate rescue medication readily available. Do not substitute abruptly for inhaled or oral corticosteroids. Does not alter the need for patients w/ aspirin-sensitive asthma to avoid taking aspirin & other NSAIDs. Neuropsychiatric events in adult, adolescent, & ped patients. Patients on therapy may present w/ systemic eosinophilia, sometimes presenting w/ clinical features of vasculitis consistent w/ Churg-Strauss syndrome. Reassess patients who develop eosinophilia, vasculitic rash, worsening pulmonary symptoms, cardiac complications, &/or neuropathy, & evaluate treatment regimens. Levocetirizine: Occurrence of somnolence, fatigue, & asthenia in patients under therapy. Avoid concurrent use w/ alcohol or other CNS depressants. Patients w/ predisposing factors of urinary retention (eg, spinal cord lesion, prostatic hyperplasia); epilepsy & at risk of convulsion. Inhibited response to allergy skin tests; require wash-out period (of 3 days) before performing allergy skin tests. Pruritus may occur when stopped even if not present before treatment initiation.