Montelukast Synthon (Montelukast)

Montelukast acts on the leukotriene pathway to manage several respiratory and allergic conditions.

• Asthma: improves long‑term control and reduces frequency of exacerbations.
• Exercise‑induced bronchoconstriction: prevents airway narrowing triggered by physical activity.
• Allergic rhinitis: alleviates nasal congestion, sneezing and itching associated with seasonal allergies.

• Montelukast selectively blocks the cysteinyl leukotriene receptor CysLT1, preventing leukotrienes D4, E4 and related mediators from binding to airway smooth‑muscle cells, submucosal glands and inflammatory cells. By inhibiting this pathway, it reduces bronchoconstriction, mucus secretion, vascular permeability and eosinophilic inflammation that contribute to asthma, exercise‑induced bronchospasm and allergic rhinitis. The antagonism is dose‑dependent and maintains its effect throughout the dosing interval.

Montelukast is generally well tolerated, but several adverse reactions have been reported.

Common Side Effects

• Headache: mild to moderate head discomfort.
• Abdominal pain: transient stomach discomfort.
• Cough: occasional dry cough.
• Nausea: mild queasiness.
• Diarrhea: loose stools.
• Fatigue: feeling of tiredness.

Serious or Rare Side Effects

• Allergic reactions: rash, urticaria or angioedema.
• Mood changes: depression, anxiety or suicidal ideation.
• Liver enzyme elevations: increased ALT or AST levels.

When prescribing Montelukast, clinicians should consider several precautionary measures to ensure safe use.

• Assess liver function: monitor hepatic enzymes in patients with liver disease.
• Review psychiatric history: observe for mood alterations or suicidal thoughts.
• Evaluate drug interactions: avoid concomitant use with strong CYP3A4 inhibitors without monitoring.
• Use caution in children: adjust dosing according to age and weight as per prescriber guidance.
• Pregnancy and lactation: discuss potential risks with the prescriber; data are limited.
• Store at ambient temperature: keep below 25 °C in original packaging, protect from moisture.

Montelukast may interact with other medicines, altering its effectiveness or safety.

Major Interactions (Avoid)

• Strong CYP3A4 inhibitors: may increase montelukast plasma levels, raising risk of adverse effects.
• Phenobarbital or rifampin: can reduce montelukast concentrations, diminishing therapeutic benefit.

Moderate Interactions (Monitor Closely)

• Antidepressants (e.g., fluoxetine): may potentiate neuropsychiatric side effects.
• Warfarin: occasional reports of altered INR; monitor coagulation parameters.
• Beta‑agonists: concurrent use may mask bronchospasm symptoms; monitor respiratory status.