Montelukast

Generic name

Montelukast

Active ingredient

Montelukast

Product type

Small-molecule medicine

Drug class

Leukotriene receptor antagonists

Brand names

UK Singulair · US Singulair

Routes

Oral

Dosage forms

Tablet, Chewable tablet, Granules

Also known as

Singulair

Usual preparations

The NHS describes tablets, chewable tablets and granules taken by mouth. (summary of the cited reference, not a prescription)

Monitoring

The MHRA advises that new or worsening mood, behaviour or sleep symptoms should be raised with the prescriber, who is advised to stop montelukast if they appear.

Availability by country

Legal status differs between countries and can change; each row cites the document it was taken from and applies only to the country named.

What it is used for

• Helping prevent asthma symptoms, usually as an add-on to a regular preventer inhaler
• Asthma triggered by exercise or by seasonal allergies
• Easing seasonal allergy symptoms such as hay fever

How it works in the body

Montelukast blocks cysteinyl leukotriene type 1 receptors, which respond to leukotrienes. StatPearls describes it as blocking leukotriene effects such as airway swelling and smooth muscle contraction, without any stimulating action of its own. StatPearls says eosinophils are the main source of cysteinyl leukotrienes, which are important in recruiting more eosinophils.

Cautions and interactions

• The MHRA warns that montelukast can cause neuropsychiatric reactions, including sleep disorders, hallucinations and changes in behaviour and mood.
• Prescribers are advised to stop montelukast if new or worsening neuropsychiatric symptoms appear.
• The NHS asks anyone who has had an allergic reaction to montelukast or another medicine to tell the doctor.
• The NHS lists epilepsy medicines such as phenobarbital or phenytoin, rifampicin and gemfibrozil as medicines to mention to a doctor or pharmacist before taking montelukast.
• UK product information says some of these can change montelukast levels.
• The NHS says montelukast can be taken in pregnancy, that it is important asthma is well controlled, and that a doctor should be told if pregnancy happens, as they may review the medicine.
• The NHS says breastfeeding is possible if a doctor, health visitor or midwife says the baby is healthy; montelukast passes into breast milk in tiny amounts and has not been known to cause side effects in breastfed babies.

Interactions

Interactions documented in the official sources cited on each card. The list covers the medicines represented on this site and is not exhaustive; how the interaction data is compiled.

No pair records for this medicine are in the sources currently represented by Anatomy Nexus. Absence from this list does not mean no interaction exists.

Same-class and related medicines

Same class: Leukotriene receptor antagonists

Medicines that share the class of Montelukast. They are separate medicines with their own licences, doses and interactions, not alternative names for Montelukast.

Related medicines

Medicines often discussed alongside Montelukast: used together, compared with it, or acting on the same problem by a different route.

Key facts

What is montelukast and how does it work?

Montelukast is a prescription medicine that helps prevent asthma symptoms. Asthma and Lung UK describes montelukast as an add-on taken alongside the regular preventer inhaler, and the NHS says it is usually prescribed when asthma is mild. The NHS says montelukast is not a rescue treatment and a reliever inhaler is used for an asthma attack. The NHS advises speaking to a doctor before stopping montelukast, because symptoms may return. The NHS and Asthma and Lung UK say it is also used when exercise or seasonal allergies trigger breathing difficulties. Asthma and Lung UK says it can improve symptoms of seasonal allergies such as hay fever. The NHS says most adults and children aged 6 months and over can take montelukast. The NHS describes tablets, chewable tablets and granules taken by mouth.

Asthma and Lung UK describes montelukast as working in a different way from steroid preventer inhalers. Montelukast blocks cysteinyl leukotriene type 1 receptors, which respond to leukotrienes. StatPearls describes it as blocking leukotriene effects such as airway swelling and smooth muscle contraction, without any stimulating action of its own. StatPearls says eosinophils are the main source of cysteinyl leukotrienes, which are important in recruiting more eosinophils.

Side effects

Common side effects listed by the NHS include diarrhoea, a raised temperature, headaches, stomach pain, feeling or being sick and a mild rash. The NHS gives self-care advice for these, such as fluids and rest, and says a pharmacist can advise. Asthma and Lung UK says montelukast has been linked to depression and anxiety and describes mental health side effects as rare but serious. The NHS lists mood changes, hallucinations, sleep problems, speech changes such as stuttering and shaking or trembling among serious side effects. An unusual or fast heartbeat, and yellowing of the skin or whites of the eyes, which can be a sign of liver problems, are also listed. For mood changes such as becoming anxious, depressed or aggressive, the NHS advises contacting a doctor or NHS 111 immediately. The NHS says to call 999 for swelling of the lips, mouth, throat or tongue, or difficulty breathing, which can signal a serious allergic reaction.

Mood, behaviour and sleep: the MHRA warning

The MHRA warns that montelukast can cause neuropsychiatric reactions, including sleep disorders, hallucinations and changes in behaviour and mood. After a review, the MHRA said the risk is unchanged but is probably not well known to healthcare professionals, patients and carers, judging by Yellow Card reports. It said more prominent warnings would be added to the leaflet supplied with every pack, and its April 2024 Drug Safety Update says the warnings in the patient leaflet and product information have been strengthened and highlighted with a black box. The MHRA advises patients to speak to their prescriber immediately, or seek urgent medical attention, if these reactions occur. Prescribers are advised to stop montelukast if new or worsening neuropsychiatric symptoms appear. The MHRA encourages patients, carers and healthcare professionals to report suspected side effects to the Yellow Card scheme.

Asthma and Lung UK advises talking to a GP or asthma nurse as soon as possible if montelukast affects sleep or mood. Asthma and Lung UK lists thoughts of suicide or self-harm as a very rare side effect. For thoughts of suicide or self-harm, the usual routes are 999 if in immediate danger, NHS 111 (mental health option) or Samaritans on 116 123, free at any time.

Pregnancy, other medicines and who needs care

The NHS says montelukast can be taken in pregnancy, that it is important asthma is well controlled, and that a doctor should be told if pregnancy happens, as they may review the medicine. The NHS says breastfeeding is possible if a doctor, health visitor or midwife says the baby is healthy; montelukast passes into breast milk in tiny amounts and has not been known to cause side effects in breastfed babies. The NHS asks anyone who has had an allergic reaction to montelukast or another medicine to tell the doctor. The NHS lists epilepsy medicines such as phenobarbital or phenytoin, rifampicin and gemfibrozil as medicines to mention to a doctor or pharmacist before taking montelukast. UK product information says some of these can change montelukast levels.

Frequently asked questions