Montelukast

Montelukast is indicated for conditions involving leukotriene‑mediated airway inflammation and allergic responses.

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

• Montelukast selectively blocks the cysteinyl leukotriene receptor CysLT1. By antagonizing this receptor, it prevents leukotriene D4 from binding, which inhibits bronchoconstriction, vascular permeability, mucus secretion and eosinophilic inflammation in the airways. This action reduces airway narrowing and inflammatory responses that underlie asthma and allergic rhinitis. The blockade is competitive and long‑lasting, allowing once‑daily dosing and contributing to improved symptom control over time.

Montelukast may cause a range of adverse reactions, most of which are mild and reversible.

Common Side Effects

• Headache: mild to moderate intensity, often transient.
• Upper respiratory tract infection: symptoms such as sore throat, nasal congestion or mild fever.
• Abdominal pain: discomfort in the stomach area, may be intermittent.
• Diarrhea: loose stools, usually self‑limiting.
• Cough: occasional dry cough without fever.

Serious or Rare Side Effects

• Allergic reactions: rash, itching, swelling, or anaphylaxis requiring immediate medical attention.
• Mood changes: depression, anxiety, or suicidal thoughts reported in rare cases.
• Hepatotoxicity: elevated liver enzymes or hepatitis, monitored by liver function tests.
• Angioedema: rapid swelling of face, lips or tongue, potentially airway‑obstructing.
• Blood disorders: eosinophilia or neutropenia, identified through blood counts.

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

• Assess asthma control: confirm that the patient’s asthma is not well‑controlled with inhaled therapy alone.
• Monitor for neuropsychiatric events: watch for mood changes, depression or suicidal thoughts.
• Evaluate liver function: consider baseline liver enzymes in patients with hepatic disease.
• Use caution in children: pediatric dosing requires careful adjustment and monitoring.
• Review concomitant medications: check for potential interactions that may alter efficacy.
• Store at ambient temperature: keep below 25°C in the original packaging, protect from moisture.

Montelukast can interact with other medicines, affecting its effectiveness or safety.

Major Interactions (Avoid)

• Rifampin: a potent CYP3A4 inducer that can markedly lower montelukast plasma concentrations, reducing clinical efficacy.
• Phenobarbital: hepatic enzyme inducer that may decrease montelukast levels, potentially compromising asthma control.

Moderate Interactions (Monitor Closely)

• Ketoconazole: strong CYP3A4 inhibitor that can increase montelukast exposure, requiring observation for enhanced effects.
• Fluconazole: moderate inhibitor of CYP3A4 that may raise montelukast levels slightly; monitor for side effects.
• Warfarin: occasional reports of altered International Normalized Ratio; check coagulation status when initiating or stopping montelukast.
• Antidepressants (SSRIs): possible additive neuropsychiatric effects; observe patients for mood changes or suicidal ideation.