Montelukast Medreg (Montelukast)

Montelukast is a leukotriene receptor antagonist used to manage conditions linked to leukotriene‑mediated airway inflammation.

• Asthma: reduces frequency of bronchospasm, improves daytime and nighttime symptom control, and decreases reliance on short‑acting bronchodilators.
• Exercise‑induced bronchoconstriction: prevents airway narrowing that occurs during or after physical activity, supporting sustained exercise performance and reducing post‑exercise symptoms.
• Allergic rhinitis: alleviates nasal congestion, sneezing, itching and watery discharge associated with seasonal or perennial allergen exposure.

• Montelukast selectively blocks the cysteinyl leukotriene receptor CysLT1, inhibiting the actions of leukotrienes D4, E4 and I4. By preventing leukotriene‑mediated bronchoconstriction, vascular permeability and eosinophilic inflammation, the drug reduces airway narrowing and inflammatory responses in the respiratory tract. This antagonism leads to decreased recruitment of inflammatory cells and reduced mucus secretion, contributing to overall improvement in airway patency. The effect is dose‑dependent and persists for 24 hours, allowing once‑daily dosing in most treatment regimens.

Montelukast may cause adverse reactions, which are categorized by frequency and severity.

Common Side Effects

• Headache: mild to moderate headache reported, usually transient and not requiring treatment.
• Abdominal pain: occasional stomach discomfort or cramps that may resolve without intervention.
• Nausea: occasional feeling of nausea, generally mild and self‑limiting.
• Upper respiratory infection: mild cold‑like symptoms such as sore throat or runny nose.
• Dizziness: occasional sensation of light‑headedness, usually transient.

Serious or Rare Side Effects

• Allergic reactions: rash, urticaria, or angioedema that may require medical attention.
• Neuropsychiatric events: agitation, depression, anxiety, or suicidal thoughts reported rarely.
• Liver enzyme elevation: occasional increase in hepatic transaminases, monitored with liver function tests.
• Blood dyscrasias: rare cases of neutropenia or thrombocytopenia reported.

When prescribing Montelukast, consider the following precautions:

• Pregnancy: safety not established; use only if potential benefit outweighs risk.
• Breastfeeding: unknown excretion; evaluate risk/benefit before use.
• Pediatric use: approved for children ≥6 months; monitor growth and development.
• Elderly: no dosage adjustment required, but monitor for neuropsychiatric effects.
• Drug interactions: review concomitant medications for potential interactions.
• Store at ambient temperature: keep below 25 °C, retain in original packaging, protect from moisture.

Montelukast may interact with several medicines; interactions are grouped by clinical significance.

Major Interactions (Avoid)

• Strong CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin): may increase montelukast plasma concentrations.
• Rifampin: potent enzyme inducer that can markedly reduce montelukast efficacy.
• Protease inhibitors (e.g., ritonavir): may raise systemic exposure and increase risk of side effects.
• Fluconazole: moderate CYP3A4 inhibition that could elevate drug levels.

Moderate Interactions (Monitor Closely)

• Phenobarbital: enzyme inducer that may lower montelukast levels; monitor asthma control.
• Warfarin: possible increase in INR; regular coagulation monitoring advised.
• Other leukotriene modifiers (e.g., zafirlukast): additive pharmacologic effect; watch for enhanced adverse reactions.