Montelukast Bristol Laboratories (Montelukast Sodium)

• Montelukast is a leukotriene receptor antagonist used to manage conditions driven by cysteinyl leukotriene activity.
• Asthma: improves long‑term control and reduces the frequency of asthma attacks.
• Allergic rhinitis: alleviates nasal congestion, sneezing and itching caused by seasonal or perennial allergens.
• Exercise‑induced bronchoconstriction: prevents airway narrowing that occurs during or after physical exertion.

• Montelukast selectively blocks the cysteinyl leukotriene receptor CysLT1, preventing leukotriene D4 and related mediators from binding. This inhibition reduces bronchoconstriction, vascular permeability, mucus secretion, and inflammatory cell recruitment in the airways, thereby improving respiratory function and reducing allergic inflammation.

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

Common Side Effects

• Headache: mild to moderate intensity.
• Abdominal pain or dyspepsia.
• Cough or throat irritation.
• Nasal congestion or rhinorrhea.
• Fatigue or somnolence.
• Mild rash or itching.

Serious or Rare Side Effects

• Allergic reactions: urticaria, angioedema, anaphylaxis.
• Neuropsychiatric events: agitation, depression, suicidal thoughts.
• Hepatotoxicity: elevated liver enzymes, hepatitis.
• Stevens‑Johnson syndrome or toxic epidermal necrolysis.
• Severe bronchospasm in rare cases.
• Blood dyscrasias: eosinophilia, neutropenia.

• When prescribing Montelukast, clinicians should consider several safety aspects.
• Monitor neuropsychiatric symptoms: watch for mood changes, depression, or suicidal ideation.
• Assess hepatic function: use caution in patients with liver impairment.
• Avoid use in acute asthma attacks: not a rescue medication.
• Check for hypersensitivity: discontinue if allergic reaction occurs.
• Pregnancy and lactation: 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, requiring attention to co‑administration.

Major Interactions (Avoid)

• Strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole): may increase montelukast levels.
• Phenobarbital or rifampicin: potent inducers that can reduce efficacy.

Moderate Interactions (Monitor Closely)

• Warfarin: potential alteration of anticoagulant effect.
• Other leukotriene modifiers (e.g., zafirlukast): additive pharmacologic effect.
• Fluconazole: may modestly increase exposure.
• Antidepressants: monitor for enhanced neuropsychiatric side effects.