Montelukast

Introduction Overview

Generic Name

montelukast

Brand Name

Singulair

Dosage Form

oral granule, oral tablet, oral chewable tablet

Drug Class

Leukotriene modifiers

Pharmacokinetics

Absorption:
Montelukast is well absorbed orally, with peak plasma concentrations typically occurring within 3 to 4 hours after administration. The bioavailability of montelukast is approximately 60-70%. Food does not significantly affect the extent of absorption, allowing for administration with or without food, which improves patient compliance. However, the rate of absorption might be slightly delayed by food intake, although this has no clinical significance. The drug’s absorption process involves passive diffusion across the gastrointestinal mucosa.

Distribution:
Montelukast is extensively bound to plasma proteins, primarily albumin, by more than 99%, which limits its distribution into the tissues and reduces free drug concentration. The volume of distribution is approximately 8 to 11 liters, indicating moderate tissue penetration. Distribution is favored in vascular tissues with active inflammatory responses given its target in leukotriene pathways, but it has limited permeability across the blood-brain barrier, minimizing central nervous system exposure.

Metabolism:
Montelukast undergoes extensive hepatic metabolism primarily via the cytochrome P450 enzyme system, including CYP3A4 and CYP2C9 isoforms. It is metabolized in the liver to several inactive metabolites through oxidation and conjugation processes. The metabolic pathways are significant in determining drug clearance and potential drug interactions with other agents metabolized by these enzymes. Genetic polymorphisms in these enzymes may affect individual metabolism rates leading to variability in plasma drug levels.

Elimination:
Montelukast is predominantly eliminated via the biliary route after hepatic metabolism. Less than 0.2% of the unchanged drug is excreted in the urine. The elimination half-life of montelukast is approximately 2.7 to 5.5 hours, which supports once-daily dosing. Clearance rates can be influenced by hepatic function but no dosage adjustments are typically required in mild to moderate hepatic impairment. There is minimal accumulation of montelukast with repeated dosing, and the drug does not exhibit significant renal excretion.

Dosage Forms

Available Dosage Forms:
- Oral tablets: 10 mg
- Chewable oral tablets: 4 mg and 5 mg
- Oral granules (packet for oral use): 4 mg

Dosages for Adults and Adolescents:
- For asthma maintenance in adults and adolescents 15 years and older: 10 mg orally once daily in the evening.
- For exercise-induced bronchoconstriction (EIB): a single 10 mg dose taken at least 2 hours before exercise; do not repeat the dose within 24 hours.

Dosages for Children:
- For asthma maintenance in pediatric patients 6 to 14 years old: 5 mg chewable tablet once daily in the evening.
- For asthma maintenance in pediatric patients 2 to 5 years old: 4 mg chewable tablet or oral granules once daily in the evening.
- For prevention of EIB in children 6 years and older: single 5 mg dose at least 2 hours before exercise.

Specific Patient Populations:
- Pediatric patients aged 6 months to 2 years: Montelukast is not typically indicated.
- Patients with hepatic impairment: No specific dose adjustment is required but should be used cautiously and monitored.
- Phenylketonuria (PKU) patients should avoid the chewable tablet formulation due to phenylalanine content.

Administering Instructions:
- Oral tablets should be swallowed whole with water.
- Chewable tablets should be chewed before swallowing.
- Oral granules can be administered directly into the mouth, mixed with a small amount of cold or room temperature soft food such as applesauce, mashed carrots, rice, or ice cream, or with breast milk or formula.
- Administer granules within 15 minutes of opening; do not save for later use.

Mechanism Of Action

Montelukast is a selective antagonist of the cysteinyl leukotriene receptor CysLT1. Leukotrienes (LTC4, LTD4, and LTE4) are inflammatory lipid mediators synthesized from arachidonic acid via the 5-lipoxygenase pathway. These leukotrienes bind to the CysLT1 receptor present on airway smooth muscle cells and other inflammatory cells, promoting bronchoconstriction, increased vascular permeability, and mucous secretion.

By selectively blocking CysLT1 receptors, montelukast prevents leukotriene binding and action, thus inhibiting leukotriene-mediated bronchoconstriction and inflammation. This action helps reduce airway edema, smooth muscle contraction, and hyperresponsiveness characteristic of asthma and allergic rhinitis.

Montelukast’s blockade of leukotrienes reduces eosinophilic inflammation and mucus production in the airways, thereby improving airflow and respiratory symptoms. It also modulates inflammatory cell recruitment and activation, contributing to its therapeutic effects in chronic asthma and exercise-induced bronchospasm.

Compared to corticosteroids and other anti-inflammatory agents, montelukast offers targeted leukotriene pathway inhibition without broad immunosuppression, providing a favorable safety profile. Clinical studies demonstrate its efficacy as an asthma controller medication, particularly when used as add-on therapy or in patients with leukotriene-driven airway inflammation. It also provides benefits in seasonal and perennial allergic rhinitis by reducing upper airway inflammation via similar mechanisms.

Pharmacological Actions

Selective antagonist of cysteinyl leukotriene receptor 1 (CysLT1 receptor) preventing leukotriene-mediated effects.
Inhibition of bronchoconstriction caused by leukotriene D4 (LTD4) in the airways.
Reduction of airway inflammation and edema through blockade of leukotriene-induced vascular permeability.
Decrease in mucous secretion from airway glands by inhibiting leukotriene stimulation.
Modulation of eosinophil recruitment and activation, lowering airway eosinophilia.
Prevention of exercise-induced bronchospasm through inhibition of exercise-triggered leukotriene release.
Improvement in pulmonary airflow and reduction of airway hyperresponsiveness.
Therapeutic effects in allergic rhinitis by attenuating leukotriene-driven nasal mucosal inflammation.
Non-immunosuppressive anti-inflammatory action, allowing use in chronic management with good safety.
Oral bioavailability facilitating easy administration once daily.
Long duration of action allowing effective 24-hour symptom control.
Synergistic potential when combined with inhaled corticosteroids or beta-agonists in asthma therapy.
Minimal central nervous system penetration reduces risk of CNS adverse effects compared to systemic corticosteroids.
No significant effect on cytochrome P450 enzymes, limiting drug interaction potential.
Efficacy in both pediatric and adult populations for asthma and allergic conditions.

Therapeutic Or Clinical Uses

Maintenance treatment of chronic asthma in adults and children aged 2 years and older.
Prevention of exercise-induced bronchoconstriction (exercise-induced asthma) in individuals 6 years and older.
Adjunctive therapy for control of seasonal allergic rhinitis symptoms when other treatments are inadequate.
Management of perennial allergic rhinitis in patients 2 years and older for relief of nasal allergy symptoms.
Reduction of asthma exacerbations and improvement of symptoms in leukotriene-driven asthma phenotypes.
Alternative to or add-on with inhaled corticosteroids in pediatric asthma management.
Prophylaxis of symptoms associated with upper respiratory allergies including sneezing, nasal congestion, and rhinorrhea.
Useful in patients with aspirin-sensitive asthma to reduce leukotriene-mediated symptoms.
Improvement of quality of life by reducing nighttime asthma symptoms and airway hyperresponsiveness.
Decreasing frequency of rescue inhaler use by controlling chronic airway inflammation.
Potential adjunct in chronic obstructive pulmonary disease (COPD) with eosinophilic inflammation (off-label).
Beneficial in patients who cannot tolerate inhaled corticosteroids or beta-agonists due to side effects.
Used in combination therapy with beta-agonists to optimize asthma symptom control.
Reduction of airway inflammation, leading to decreased hospitalizations and emergency room visits.
Management of allergic airway disease symptoms in both pediatric and adult patients.

Side Or Adverse Effects

Common side effects include headache and abdominal pain.
Gastrointestinal disturbances: diarrhea, nausea, and dyspepsia.
Upper respiratory tract symptoms such as nasal congestion, sore throat, and cough.
Flu-like symptoms including fever and malaise.
Ear pain or sensation of fullness in the ear, sometimes with transient hearing disturbances.
Neuropsychiatric events: agitation, anxiety, depression, irritability, confusion, aggression, hallucinations, and suicidal thoughts or behaviors reported.
Sleep disturbances including vivid dreams, insomnia, nightmares, and sleepwalking.
Musculoskeletal symptoms like tremors and muscle cramps.
Allergic reactions: rash, urticaria, pruritus, and rarely angioedema or anaphylaxis.
Signs of eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome) may occur, presenting with vasculitis symptoms.
Rare neurological side effects such as stuttering and tremors.
Potential hypersensitivity reactions including severe skin reactions (blisters, severe itching).
Behavioral changes particularly in pediatric populations and adolescents.
Post-marketing reports of increased risk of neurobehavioral symptoms warrant close monitoring.
Rarely, elevation of liver enzymes suggesting hepatic involvement.
Generally well tolerated with low incidence of serious adverse effects.

Precautions

Monitor for neuropsychiatric symptoms including mood changes, depression, and suicidal ideation.
Use caution in patients with a history of mental health disorders or psychosis.
Avoid abrupt discontinuation of corticosteroids when initiating montelukast; taper steroids as advised by healthcare professional.
Patients with phenylketonuria (PKU) should avoid chewable tablets due to phenylalanine content.
Evaluate for signs of eosinophilic granulomatosis with polyangiitis, especially during corticosteroid taper.
Caution when co-administering with drugs metabolized by CYP enzymes due to potential metabolic interactions.
Not suitable for acute asthma attacks; inform patients that montelukast is not a rescue medication.
Use caution in hepatic impairment and monitor liver function tests periodically if clinically indicated.
Avoid concurrent use with aspirin or NSAIDs in aspirin-sensitive asthma due to risk of bronchospasm.
Pregnancy and breastfeeding: use only if clearly needed and after risk/benefit assessment.
Ensure correct administration of oral granules, avoid mixing with unsuitable liquids to preserve drug stability.
Pediatric dosing precision important to avoid overdose or subtherapeutic exposure.
Educate patients regarding adherence to once-daily dosing for optimal therapeutic effect.
Monitor for hypersensitivity reactions and discontinue if severe allergic response occurs.
Patients should be advised to report any signs of mood or behavioral changes immediately.

Warnings

Stop montelukast and contact healthcare provider immediately if unusual mood or behavior changes occur, including agitation, depression, hallucinations, or suicidal thoughts.
Monitor for signs of blood vessel inflammation (vasculitis) such as flu-like symptoms, sinus pain, rash, numbness, or tingling in limbs.
Montelukast is not indicated as a rescue treatment for acute bronchospasm or asthma attacks.
Risk of neuropsychiatric events observed post-marketing; vigilant monitoring necessary, especially in pediatric patients.
May cause serious allergic reactions, including anaphylaxis; discontinue immediately if signs develop.
Use with caution in patients with history of severe allergic or anaphylactic reactions to the drug.
Avoid in patients with known hypersensitivity to montelukast or any component of the formulation.
May precipitate eosinophilic granulomatosis with polyangiitis, particularly when corticosteroid therapy is reduced.
Patients experiencing worsening respiratory symptoms should seek immediate medical attention.
Abrupt stopping of corticosteroids upon starting montelukast can cause asthma exacerbations; taper steroids gradually.
Potential for sleep disturbances or vivid dreams warrants caution in patients with existing sleep disorders.
May cause rare but serious liver injury; if signs of hepatic dysfunction emerge, discontinue drug.
Beware of potential behavioral side effects in pediatric populations; caregivers should monitor closely.
Montelukast can mask symptoms without treating acute inflammation, possibly delaying appropriate emergency treatment.
Pregnancy category B: safety in pregnancy not fully established; use only if benefit outweighs risk.

Contraindication

Known hypersensitivity to montelukast or any component of the formulation.
Patients with previous severe allergic reaction to montelukast (e.g., anaphylaxis, angioedema).
Use in pediatric patients under 2 years of age for asthma due to lack of established safety and efficacy.
Avoid chewable tablet in patients with phenylketonuria due to phenylalanine content.
Contraindicated as a rescue treatment for acute bronchospasm or status asthmaticus.
Concurrent use contraindicated if patient shows hypersensitivity to similar leukotriene receptor antagonists.
Patients with a history of suicidal ideation or severe psychiatric illness should use cautiously or consider alternatives.
Patients with severe hepatic impairment without prior evaluation.
Do not use in uncontrolled acute asthma exacerbations requiring urgent intervention.
Avoid in patients with known vasculitis attributed to hypersensitivity to montelukast.
Not recommended during breastfeeding unless clearly necessary and prescribed by specialist.
Contraindicated in patients with hypersensitivity to any excipients present in granule or tablet formulations.
Avoid repeated dosing within 24 hours for prevention of exercise-induced bronchospasm due to risk of overdose.
Use cautiously or avoid in combination with drugs that may cause additive neuropsychiatric effects.
Contraindicated in patients who have previously experienced severe mood or behavior disturbances on montelukast.

Drug Interactions

Montelukast is metabolized primarily via CYP3A4 and CYP2C9; concurrent use with inducers or inhibitors of these enzymes may alter montelukast plasma levels.
Co-administration with phenobarbital may decrease montelukast plasma concentrations due to enzyme induction.
Rifampin and other CYP inducers may reduce montelukast effectiveness by increasing metabolic clearance.
Use with warfarin has not demonstrated significant interaction, but monitoring INR is advisable due to limited reports.
No significant interaction with albuterol or inhaled corticosteroids, allowing combination therapy in asthma management.
NSAIDs do not have a direct pharmacokinetic interaction but should be used cautiously in aspirin-sensitive patients with asthma.
No reported interaction with common antihistamines, although additive effects on sedation or CNS symptoms should be considered.
The drug interaction potential with hepatic enzyme inhibitors such as ketoconazole may theoretically raise montelukast levels.
Montelukast does not significantly inhibit or induce major CYP enzymes, reducing risk of interactions with many drugs.
Herbal products like St. John's Wort may induce CYP enzymes and reduce montelukast efficacy.
No significant interaction with common vitamins or supplements.
Co-administration with theophylline shows no significant pharmacokinetic interaction but monitor for additive side effects.
Caution is advised when combining montelukast with neuropsychiatric drugs because of the potential for additive behavioral side effects.
Montelukast may interact with certain antidepressants or antipsychotics indirectly affecting metabolism.
No evidence of significant interaction with oral contraceptives.

Preparations Of The Drug

Montelukast Sodium Oral Tablets, USP: 10 mg film-coated tablets for adults and adolescents aged 15 years and older.
Montelukast Sodium Chewable Tablets: 4 mg and 5 mg sizes for pediatric use in children 2 to 14 years.
Montelukast Sodium Oral Granules: 4 mg packets for pediatric patients aged 6 months to 5 years, designed for mixing with soft food or formula.
Tablets and granules formulated with excipients ensuring stability and palatability in pediatric formulations.
Chewable tablets contain phenylalanine, important for phenylketonuria patients to consider.
Film coating on tablets facilitates easy swallowing and protects against moisture.
Granules packaged in single-use foil packs to maintain drug integrity until use.
All preparations are designed for once-daily dosing to improve adherence.
Available commercially under the brand name Singulair and as generic formulations.
Packaging includes detailed patient instructions, particularly for proper use of granules and chewable tablets.
Shelf life typically ranges from 24 to 36 months when stored at room temperature away from moisture and heat.
Manufactured under current Good Manufacturing Practices (cGMP) to ensure quality and consistency.
Various strengths provided to enable dosing flexibility according to age and clinical indication.
Preparations do not require refrigeration and should be stored in a dry place.
Each preparation includes patient information leaflets emphasizing proper use and potential side effects.