Montelukast

Key facts

• Montelukast (sold as Singulair and in generic form) is a leukotriene receptor antagonist used to prevent asthma symptoms and to treat allergic rhinitis (hay fever).
• Take it once daily, generally in the evening for asthma, whether or not you have symptoms that day; it needs regular use to build its preventive effect.
• It does not relieve a sudden asthma attack. Keep using your fast-acting reliever inhaler for sudden breathlessness or wheeze.
• Montelukast carries a boxed warning for neuropsychiatric effects, including agitation, aggression, nightmares, depression, and rare suicidal thoughts or actions, in both adults and children.

What montelukast treats

Montelukast treats asthma, taken daily to prevent symptoms and reduce exercise-induced breathlessness, and allergic rhinitis, easing sneezing, congestion, and itching from seasonal or year-round allergies. It is a preventer, not a rescue treatment, and it will not stop a breathing emergency already underway.

How montelukast works

Montelukast blocks leukotriene receptors in the airways. Leukotrienes are chemicals released during allergic and asthmatic reactions that narrow airways, trigger mucus production, and cause swelling. Blocking their receptor reduces these effects, but because it works gradually, it needs daily dosing rather than use as a rescue medicine.

Before you take it

• Do not take montelukast if you have had an allergic reaction to it before.
• Tell your prescriber about any history of depression, anxiety, or self-harm before starting, and report any new mood or behaviour changes promptly once you begin.
• Do not stop or reduce any other asthma medicine, including inhaled steroids, without medical advice, even if montelukast seems to be controlling your symptoms.
• Some chewable tablets contain phenylalanine; tell your prescriber if you have phenylketonuria.

Side effects

Common effects include headache, stomach pain, cough, and, in children, fever or diarrhoea.

Stop and seek urgent medical care for any of these:

• Agitation, aggression, nightmares, depression, hallucinations, or thoughts of self-harm, at any age, but watch children and teenagers closely.
• Severe allergic reaction: hives, facial or throat swelling, difficulty breathing.
• Numbness or tingling in the limbs, worsening sinus symptoms, or a new rash, which can rarely signal a serious inflammatory condition.
• Worsening breathing despite taking montelukast; this needs your reliever inhaler and urgent review, not more montelukast.

Safety essentials

• Tell your prescriber immediately about any new mood, behaviour, or sleep change, and stop montelukast if these become severe; this boxed warning applies even when montelukast is used only for allergies.
• Montelukast is not a reliever. Always keep a fast-acting inhaler on hand for sudden symptoms, and seek emergency care if an attack does not respond to it.
• Continue your other prescribed asthma treatments, including inhaled steroids, unless your prescriber tells you to stop; montelukast is an add-on, not a replacement.
• Take it at the same time each day, since consistent daily use, not occasional dosing, is what gives montelukast its preventive effect.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.