Leukotriene receptor antagonistPrescription only

Montelukast

Tablet, chewable tablet or granules

Quick Summary

Montelukast blocks chemicals called leukotrienes that cause the airways to narrow and swell. It's used alongside inhalers to prevent asthma symptoms.

Asthma prevention
Exercise-induced asthma
Hay fever

Medical Uses

Asthma prevention: Added to inhalers when asthma isn't well controlled.
Exercise-induced asthma: Helps prevent symptoms brought on by exercise.
Hay fever: Eases sneezing and a runny or blocked nose from allergies.

How it's taken

Montelukast is usually taken once a day, often in the evening. Chewable tablets and granules are used for children. Your doctor decides the right dose for you and may change it over time.

Take it every day, even when you feel well. It doesn't work fast enough for an asthma attack: always keep your reliever inhaler with you.

Your doctor decides the right dose for you. Follow their instructions and the label.

Common Side Effects

Headache

One of the more common side effects.

Tummy pain

Some people get stomach ache or feel thirsty.

Sleep problems

Unusual dreams, nightmares or trouble sleeping.

Interactions

Phenobarbital

Can reduce how well montelukast works.

Rifampicin

May lower montelukast levels in the blood.

Critical Warnings

Mood and behaviour changes

Black Box Warning: Rarely causes agitation, depression, sleepwalking or thoughts of self-harm, in children and adults. Stop and contact a doctor straight away if you notice these.

Not for asthma attacks

Use your reliever inhaler for sudden symptoms and get emergency help if it isn't working.

Sources and further reading

Last updated 21 October 2026. For more detail, see these trusted health organisations.

Related Topics

Asthma