Montelukast: A leukotriene receptor antagonist

What it is

Montelukast is a selective antagonist of the CysLT1 leukotriene receptor. Leukotrienes are inflammatory mediators released by mast cells and eosinophils that cause bronchoconstriction, mucosal oedema and bronchial hyperreactivity.

It is taken by mouth, which helps adherence, and it is useful in asthma with allergic rhinitis and in exercise-induced bronchospasm. It is less effective than inhaled corticosteroids, which remain the basis of treatment; montelukast is an add-on. The medicines agencies have strengthened their warnings about neuropsychiatric effects.

Mechanism of action

It antagonises:

CysLT1 leukotriene receptors in bronchial cells and the airways
It reduces leukotriene-induced bronchoconstriction and oedema
Especially useful in allergic and exercise-induced asthma

At the counter

When to recommend it

Mild to moderate persistent allergic asthma
Exercise-induced asthma (taken 2 h before)
Asthma + allergic rhinitis (it improves both)
Add-on in asthma not well controlled with other treatments

When not to

Allergy to montelukast
Severe liver failure
History of psychiatric disorder: discuss with the doctor because of the neuropsychiatric risk
It does not work for an acute attack

What to say at the counter. When supplying it, the warning that cannot be missed: 'If you notice mood changes, nightmares, insomnia or strange thoughts —in children too— get it checked.' And remind them that it does not replace the maintenance inhaler or work in an attack.

Warnings

Important Neuropsychiatric effects: agitation, nightmares, insomnia, depression and, uncommonly, suicidal thoughts, in children too. The agencies have strengthened the warning: ask about them.
Important Eosinophilic granulomatosis with polyangiitis (Churg–Strauss): very rare, often when oral corticosteroids are withdrawn. Keep watch.
Caution It is not a reliever: in an attack a fast-acting bronchodilator is needed.
Caution It does not replace the inhaled corticosteroid as the basic asthma treatment.

Pharmacokinetics

Absorption: Rapid oral absorption. Bioavailability of 64–73%, barely affected by food. Peak at 3–4 hours.
Distribution: Wide distribution. Protein binding above 99%. It crosses the placenta.
Metabolism: Extensive hepatic metabolism. It produces less active metabolites.
Elimination: Mainly biliary. Half-life of 2.7–5.5 hours.

Montelukast vs inhaled budesonide

Aspect	Montelukast	Inhaled budesonide
Route	Oral	Inhaled
Anti-inflammatory potency	Moderate	High
Adherence	Easier (oral)	Needs inhaler technique
Allergic asthma	Useful as an add-on	First choice
Exercise-induced asthma	Useful (even 2 h before)	Improves baseline control

Montelukast is a useful add-on in allergic asthma. Budesonide is more potent as a single treatment.

Self-assessment

Three questions. When you check your answers you will see the explanation for each one.

What is montelukast's mechanism of action? It inhibits histamine synthesis It blocks β2 adrenergic receptors It antagonises leukotriene receptors (CysLT1), reducing inflammation
A patient with exercise-induced asthma takes montelukast. When should they take it? Both are valid options Every day as prevention 2 hours before exercise
Why is montelukast particularly useful in allergic asthma? Because leukotrienes are key mediators of allergic inflammation, and blocking them works well Because it kills allergenic bacteria Because it is cheaper

Training content. It does not replace the summary of product characteristics or clinical judgement.

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