The most frequently reported adverse effects with montelukast include upper respiratory infection, fever, headache, pharyngitis, cough, abdominal pain, diarrhea, otitis media, influenza, rhinorrhea, sinusitis, and otitis.
Infection and infestations: Pyuria, skin infection, tooth infection, varicella, viral infection.
Blood and lymphatic system disorders: Increased bleeding tendency, thrombocytopenia.
Immune system disorders: Hypersensitivity reactions including anaphylaxis.
Psychiatric disorders: Agitation including aggressive behavior or hostility, anxiousness, depression, disorientation, disturbance in attention, dream abnormalities, hallucinations, insomnia, irritability, memory impairment, restlessness, somnambulism, suicidal thinking and behavior (including suicide), tic, tremor.
Nervous system disorders: Dizziness, drowsiness, hyperkinesia, hypoesthesia, paresthesia, seizure.
Eye disorders: Conjunctivitis, myopia.
Ear and labyrinth disorders: Ear pain.
Cardiac disorders: Palpitations.
Vascular disorders: Vasculitis.
Respiratory, thoracic and mediastinal disorders: Acute bronchitis, asthma, Churg-Strauss syndrome, epistaxis, laryngitis, nasal congestion, pneumonia, pulmonary eosinophilia, rhinitis/infective rhinitis, sinus headache, tonsillitis, wheezing.
Gastrointestinal disorders: Dry mouth, dyspepsia, gastroenteritis/infectious gastroenteritis, nausea, pancreatitis, vomiting.
Hepatobiliary disorders: Hepatic infiltration eosinophilic, hepatitis cholestatic, hepatocellular liver injury, mixed-pattern liver injury, increased alanine aminotransferase (ALT) and aspartate aminotransferase (AST).
Skin and subcutaneous tissue disorders: Angioedema, atopic dermatitis, bruising, dermatitis, eczema, erythema multiforme, erythema nodosum, Stevens-Johnson syndrome, pruritus, rash, toxic epidermal necrolysis, urticaria.
Musculoskeletal and connective tissue disorders: Arthralgia, myalgia including muscle cramps.
Renal and urinary disorders: Enuresis in children.
General disorders and administration site conditions: Asthenia, dental pain, edema, fatigue, leg pain, malaise, thirst.
Injury, poisoning and procedural complications: Trauma.