Montelukast Medreg (Montelukast)

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

• Asthma: reduces frequency of symptoms, improves lung function, and decreases need for rescue inhalers.
• Allergic rhinitis: alleviates nasal congestion, sneezing and itchy eyes caused by seasonal or perennial allergens.
• Exercise‑induced bronchoconstriction: prevents airway narrowing during or after physical activity, supporting better exercise tolerance.

• Montelukast selectively blocks the cysteinyl leukotriene receptor CysLT1 on airway smooth‑muscle cells, mast cells and eosinophils. By antagonizing this receptor, it prevents leukotriene D4‑mediated bronchoconstriction, vascular permeability and inflammatory cell recruitment, thereby reducing airway inflammation and hyper‑responsiveness associated with asthma and allergic diseases. The inhibition is competitive and reversible, allowing normal leukotriene signaling to resume when the drug concentration declines.

Montelukast is generally well tolerated, but a range of adverse reactions have been reported.

Common Side Effects

• Headache: mild to moderate intensity, often transient.
• Upper respiratory tract infection: symptoms such as sore throat or nasal congestion.
• Abdominal pain: occasional discomfort or cramping.
• Diarrhea: loose stools that usually resolve without intervention.
• Cough: non‑productive cough reported in some patients.

Serious or Rare Side Effects

• Allergic reactions: rash, urticaria or angioedema requiring medical attention.
• Mood changes: depression, anxiety or suicidal thoughts observed in rare cases.
• Hepatotoxicity: elevated liver enzymes or hepatitis, monitored through labs.
• Stevens‑Johnson syndrome: severe skin reactions with blistering and mucosal involvement.
• Churg‑Strauss syndrome: rare vasculitic disorder associated with eosinophilia.

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

• Assess patient history: review asthma control level and prior leukotriene antagonist response.
• Monitor for neuropsychiatric symptoms: observe mood changes, depression or suicidal ideation.
• Evaluate liver function: consider baseline liver enzymes in patients with hepatic disease.
• Use caution in children: adjust monitoring for pediatric patients and follow prescriber guidance.
• Avoid use in patients with known hypersensitivity to montelukast or any tablet excipients.
• Store at ambient temperature: keep below 25 °C, retain in original packaging, protect from moisture.

Montelukast may interact with other medicines, altering its effectiveness or increasing risk of adverse effects.

Major Interactions (Avoid)

• Phenobarbital, carbamazepine, phenytoin: enzyme inducers that can reduce montelukast plasma levels.
• Ritonavir or other strong CYP3A4 inhibitors: may increase montelukast exposure and risk of side effects.

Moderate Interactions (Monitor Closely)

• Warfarin: potential alteration of anticoagulant effect, monitor INR.
• Theophylline: possible additive bronchodilator effect, observe for increased tremor.
• Fluconazole: moderate CYP3A4 inhibition may raise montelukast concentrations.
• Antidepressants (SSRIs): monitor for enhanced neuropsychiatric adverse events.