A leukotriene receptor antagonist (asthma/allergy tablet)
Montelukast
A once-daily tablet that helps control asthma and hay fever by blocking inflammatory chemicals — useful as an add-on, but carries a warning about mood and behaviour changes.
What is Montelukast?
Montelukast is a leukotriene receptor antagonist taken as a tablet or granules. It is used as an add-on treatment in asthma and to help with allergic symptoms, calming inflammation that narrows the airways.
Education and reference only. This is a plain-language guide to Montelukast — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Montelukast is a leukotriene receptor antagonist, taken as a tablet (or as chewable tablets or granules for children). It is used as an add-on in asthma — often alongside inhalers — and helps with allergic rhinitis (hay fever) symptoms at the same time. It can be particularly helpful where allergy or exercise-triggered asthma is prominent. It is a preventer-type treatment taken regularly, not a quick reliever.
How it works
When the airways and nose react to triggers, the body releases inflammatory chemicals called leukotrienes, which tighten the airways, increase mucus and drive swelling and a runny, blocked nose. Montelukast blocks the receptor those chemicals act on, so their effects are reduced — easing airway narrowing and inflammation in asthma and calming hay-fever symptoms. Because it is a tablet, it treats the nose and the chest together, which can be convenient when both are involved.
Company & origin
Originated / developed by: Merck (discovered at Merck Frosst, Canada).
Montelukast is a leukotriene receptor antagonist discovered by scientists at Merck Frosst in Canada and developed by Merck & Co. It received US FDA approval in February 1998 and is marketed as Singulair.
What it treats
Conditions Montelukast is used for
Practical use
How to take Montelukast
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Usually taken once a day in the evening, as a tablet, chewable tablet or granules depending on age.
- Take it regularly as a preventer rather than for sudden symptoms; keep your reliever inhaler for attacks.
- Be aware of mood and behaviour changes (such as low mood, anxiety, sleep problems, vivid dreams or, rarely, suicidal thoughts) and report these promptly, as they can occur with this medicine.
- If you miss a dose, skip it and take the next one at the usual time; do not take two doses together.
- Granules for young children can be given directly or mixed with a small amount of soft cold food.
Weighing it up
Advantages & disadvantages of Montelukast
Advantages
- Taken as a tablet or granules by mouth, which suits people who struggle with inhalers.
- Useful add-on when inhaled treatment alone is not enough.
- Can help allergic rhinitis symptoms as well as asthma.
- Convenient once-daily dosing in the evening.
Disadvantages
- Can cause neuropsychiatric effects such as low mood, anxiety, sleep disturbance and, rarely, suicidal thoughts.
- Does not work for everyone and is generally less effective than inhaled steroids for asthma control.
- Is not a reliever and will not help during a sudden attack.
- May cause headache, stomach upset or vivid dreams in some people.
Practical use
Good to know
It is taken regularly, once a day, often in the evening, and works best as part of an overall asthma plan rather than on its own. The most important thing to know is a safety warning: montelukast can cause neuropsychiatric effects — changes in mood or behaviour, vivid dreams or sleep disturbance, anxiety or low mood, and rarely thoughts of self-harm or suicide. These can affect adults and children. The MHRA advises being alert to them, and if they occur the medicine should usually be stopped and reviewed — so tell your prescriber promptly about any new mood, behaviour or sleep changes.
Who should not take it / use with caution
- People who have had a serious reaction to it before.
- Used with particular care in anyone with a history of mental-health problems, and parents/carers should be alert to mood or behaviour changes in children.
- It is not a reliever and must not be used to treat a sudden asthma attack.
Monitoring
- Asthma and hay-fever control
- Any new mood, behaviour, sleep or anxiety changes (in adults and children)
- Overall response and whether it is still adding benefit
Side effects
- Neuropsychiatric effects — sleep disturbance and vivid dreams or nightmares, mood or behaviour changes, anxiety, agitation, low mood, and rarely suicidal thoughts; these should be reported and the medicine reviewed.
- Headache, tummy ache or digestive upset.
- Occasionally thirst, rash, or cold-like symptoms; rarely, more serious allergic reactions.
Key interactions
- Generally few significant interactions, but certain medicines (for example some epilepsy medicines and rifampicin) can lower its levels.
- It works alongside, not instead of, inhaled treatments for asthma.
- Tell your prescriber about all your medicines, including those for mental health, so the overall picture is considered.
Available as: Tablets, plus chewable tablets and oral granules for children. Taken once a day, commonly in the evening.
Answers
Montelukast: frequently asked questions
What are the mood or behaviour changes I've been warned about?
Montelukast can occasionally cause neuropsychiatric effects: sleep problems and vivid dreams or nightmares, irritability, anxiety, agitation, low mood, and rarely thoughts of self-harm or suicide. The MHRA has specifically warned about these. They can affect both adults and children, so be alert to any new changes and report them promptly — the medicine is usually stopped and reviewed if they occur.
Should I stop montelukast if I notice these changes?
Contact your prescriber promptly and don't simply continue. In most cases the medicine is stopped and your asthma treatment reviewed. If anyone has thoughts of self-harm or suicide, seek urgent help straight away. Don't leave asthma untreated either — your team will arrange an alternative.
Is montelukast a reliever or a preventer?
It is a regular, preventer-type treatment — taken every day to help keep asthma and hay fever under control — not a quick-acting reliever. If you have a sudden attack you still need your fast-acting reliever inhaler, and you should keep taking your inhaled preventer as prescribed.
Why is it usually taken in the evening?
Montelukast is commonly taken in the evening, which suits its use in asthma and can help with night-time and early-morning symptoms. Take it at a consistent time each day as your prescriber advises, whether or not you currently have symptoms, so the protective effect is maintained.
What is the difference between montelukast and Singulair?
They are the same medicine — montelukast is the generic (active-ingredient) name and Singulair is a brand name. Generic montelukast contains the identical active ingredient.
The wider class
About Leukotriene receptor antagonists
Montelukast belongs to the leukotriene receptor antagonists class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
Browse by body system
Authoritative sources
- BNF: Montelukast.
- electronic Medicines Compendium (SmPC): Montelukast (Singulair).
- NICE CKS: Montelukast.
- MHRA Drug Safety Update: Montelukast (Singulair) — reminder of the risk of neuropsychiatric reactions.
Building a medicines information resource?
We create evidence-led, dose-free drug and formulary references for teams.