Answer
Common gastrointestinal side effects listed with montelukast include abdominal pain in clinical studies and diarrhoea, nausea and vomiting, with the latter three also reported as common with placebo.
Sources for this answer
- Singulair Paediatric 5 mg Chewable TabletsOrganon Pharma (UK) Limited · emc · SmPC §4.8 Undesirable effects · Version 19Document updated
Sources checked