In clinical studies with SINGULAIR 4 mg granules, the most commonly reported side effects (occurring in at least 1 of 100 patients and less than 1 of 10 paediatric patients treated) thought to be related to SINGULAIR were: • diarrhoea • hyperactivity • asthma • scaly and itchy skin • rash Additionally, the following side effects were reported in clinical studies with either SINGULAIR 10 mg film-coated tablets, 5 mg or 4 mg chewable tablets: • abdominal pain • headache • thirst These were usually mild and occurred at a greater frequency in patients treated with SINGULAIR than placebo (a pill containing no medication).