Montelukast Krka (Montelukast)

Montelukast is indicated for conditions involving leukotriene‑mediated inflammation, primarily within the respiratory tract.

• Asthma: improves long‑term control and reduces exacerbations in adults and children.
• Allergic rhinitis: relieves nasal congestion, sneezing and itching associated with seasonal or perennial allergies.
• Exercise‑induced bronchospasm: prevents airway narrowing triggered by physical activity.

• Montelukast selectively antagonizes the cysteinyl leukotriene‑type 1 (CysLT1) receptor, inhibiting the actions of leukotrienes C4, D4 and E4. By blocking these mediators, it reduces bronchial smooth‑muscle contraction, vascular permeability, mucus secretion and eosinophilic inflammation, thereby improving airway patency and decreasing hypersensitivity responses. The effect is dose‑dependent and contributes to both prophylactic and maintenance therapy in chronic respiratory diseases. It does not exhibit significant bronchodilator activity on its own.

Montelukast may cause a range of adverse reactions, varying from mild to serious.

Common Side Effects

• Headache: mild to moderate intensity.
• Abdominal pain: discomfort or cramps in the stomach area.
• Cough: non‑productive respiratory irritation.
• Nasopharyngitis: inflammation of the nasal passages and throat.
• Dyspepsia: indigestion with bloating or nausea.
• Diarrhea: loose stools.
• Fatigue: feeling of tiredness.
• Dizziness: light‑headed sensation.
• Nausea: feeling of sickness.

Serious or Rare Side Effects

• Allergic reactions: rash, angioedema or anaphylaxis requiring immediate medical attention.
• Neuropsychiatric events: agitation, depression, suicidal thoughts or behavior.
• Hepatotoxicity: elevated liver enzymes or hepatitis.
• Eosinophilic granulomatosis with polyangiitis: rare vasculitic disorder.
• Stevens‑Johnson syndrome: severe skin reaction.

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

• Assess asthma control: confirm that the patient requires add‑on therapy before initiation.
• Monitor neuropsychiatric symptoms: watch for mood changes, depression or suicidal thoughts.
• Avoid in hypersensitivity: discontinue if signs of allergic reaction appear.
• Use with caution in hepatic impairment: dose adjustment may be needed in severe liver disease.
• Review concomitant drugs: consider potential interactions that may alter montelukast levels.
• Store at room temperature: keep in the original packaging, protect from moisture and heat.

Montelukast can interact with other medicines, affecting its plasma concentration or therapeutic effect.

Major Interactions (Avoid)

• Ritonavir: strong CYP3A4 inhibition markedly increases montelukast exposure.
• Phenobarbital, carbamazepine, phenytoin: potent CYP inducers markedly decrease montelukast levels.
• Gemfibrozil: may increase montelukast concentrations leading to toxicity.

Moderate Interactions (Monitor Closely)

• Fluconazole: moderate CYP3A4 inhibition may raise montelukast levels.
• Ketoconazole: similar effect requiring observation.
• Warfarin: potential alteration of anticoagulant effect; monitor INR.
• St. John’s wort: herbal inducer that can reduce efficacy.