Montelukast sodium is generally well tolerated. However, following are the adverse effects reported which usually were mild and did not require discontinuation of therapy. Hypersensitivity reactions (including anaphylaxis, angioedema, rash, pruritus, urticaria and very rarely, hepatic eosinophillic infiltration).
Dream abnormalities, hallucinations, palpitations, drowsiness, irritability, restlessness, insomnia, increased sweating and headache.
Other adverse effects include nausea, vomiting, dyspepsia, diarrhea, abdominal pain, myalgia including muscle cramps, increased bleeding tendency, bruising edema, tremor, dry mouth, vertigo and arthralgia.