According to clinical studies (the results of treatment with montelukast at age doses of 5194 children under 15 and 5195 teenagers ≥15 years and adults), headache, abdominal pain, dry mouth (at a frequency of ≥1 / 100 to <1/10).
According to the World Health Organization (WHO), unwanted effects are classified according to their frequency of development as follows: very often (≥1/10), often (from ≥1 / 100 to <1/10), infrequently (from ≥1 / 1,000 to <1/100), rarely (from ≥1 / 10,000 to <1 / 1,000), very rarely (<1 / 10,000); frequency is unknown - according to available data, it was not possible to establish the frequency of occurrence.
Infectious and parasitic diseases:
very often: infections of the upper respiratory tract.
From the immune system:
infrequently: hypersensitivity reactions, including anaphylaxis;
rarely: angioedema;
very rarely: eosinophilic liver infiltration.
From the skin and subcutaneous tissue:
often: rash;
infrequent: tendency to form hematomas, hives, itching;
very rarely: erythema nodosum, erythema multiforme.
From the central nervous system:
infrequently: headache, dizziness, drowsiness, paresthesia / hypoesthesia, convulsions.
Mental disorders:
infrequent sleep disorders (including nightmares), insomnia, somnambulism, irritability, anxiety, agitation (including aggressive behavior or hostility), psychomotor hyperactivity (including irritability, anxiety and tremor), depression;
rarely: violation of attention, memory impairment;
very rarely: hallucinations, disorientation, suicidal thoughts and suicidal behavior.
From the cardiovascular system:
rare: heartbeat.
From the side of the blood and lymphatic system:
rarely: increased tendency to bleeding.
From the gastrointestinal tract (GIT):
often: abdominal pain, diarrhea, nausea, vomiting, pancreatitis;
infrequently: indigestion, dryness of the oral mucosa.
From the liver and bile ducts:
often: increased activity of "hepatic" transaminases (alanine aminotransferase (ALT), aspartate aminotransferase, (ACT));
very rarely: hepatitis (including cholestatic, hepatocellular and mixed liver damage).
From the side of the musculoskeletal and connective tissue:
infrequently: arthralgia, myalgia (including muscle cramps).
From the respiratory system:
infrequently: nosebleeds;
very rarely: the Charge-Strauss syndrome, pulmonary eosinophilia.
Other:
often: hyperthermia;
infrequently: asthenia / fatigue, malaise, swelling.