Montelukast

• Montelukast is a leukotriene receptor antagonist used to treat conditions mediated by cysteinyl leukotrienes.
• Asthma: improves control of chronic asthma and reduces the frequency of exacerbations.
• Allergic rhinitis: relieves nasal congestion, sneezing and itching associated with seasonal or perennial allergies.
• Exercise‑induced bronchoconstriction: prevents airway narrowing that occurs during or after physical activity.

• Montelukast selectively blocks the cysteinyl leukotriene receptor CysLT1, preventing leukotriene D4 from binding. This inhibition reduces leukotriene‑mediated bronchoconstriction, vascular permeability, and inflammatory cell recruitment in the airways, thereby improving airflow and decreasing allergic inflammation.

Montelukast is generally well tolerated, but adverse reactions can occur.

Common Side Effects

• Headache: mild to moderate intensity.
• Abdominal pain: occasional discomfort.
• Cough: transient irritation.
• Sore throat: mild irritation of the pharynx.
• Nausea: occasional upset stomach.
• Dizziness: occasional light‑headedness.

Serious or Rare Side Effects

• Allergic reactions: angioedema, anaphylaxis, or severe rash.
• Mood changes: depression, agitation, or suicidal thoughts.
• Hepatic effects: elevated liver enzymes or hepatitis.
• Stevens‑Johnson syndrome: severe skin detachment.
• Severe rash: drug reaction with eosinophilia and systemic symptoms (DRESS).
• Respiratory distress: paradoxical worsening of asthma symptoms.

• When prescribing Montelukast, clinicians should consider several safety measures.
• Monitor mood: watch for depression, anxiety, or suicidal ideation.
• Assess liver function: consider baseline and periodic liver enzyme testing.
• Review asthma control: ensure patients have an appropriate rescue inhaler.
• Avoid in hypersensitivity: do not use in patients with known allergy to Montelukast or excipients.
• Pregnancy and lactation: safety data are limited; use only if benefit outweighs risk.
• Store below 25°C: keep in the original packaging, protect from moisture and direct sunlight.

Montelukast may interact with other medicines that affect its metabolism or pharmacodynamic profile.

Major Interactions (Avoid)

• Ritonavir (strong CYP3A4 inhibitor): may increase Montelukast plasma levels.
• Phenobarbital (enzyme inducer): may reduce therapeutic effect.

Moderate Interactions (Monitor Closely)

• Fluconazole (moderate CYP3A4 inhibitor): may modestly raise levels.
• Erythromycin (CYP3A4 inhibitor): potential increase in exposure.
• Carbamazepine (enzyme inducer): may lower effectiveness.
• Warfarin: monitor INR as Montelukast can occasionally affect anticoagulation.