Montelukast

What is montelukast?

Montelukast is a prescription medicine used to treat and prevent asthma and allergy symptoms. It is often sold under the brand name Singulair and is part of a group of medicines called leukotriene receptor antagonists[1]. 

What is montelukast used to treat?

It is used to[1]: 

• Prevent asthma symptoms, especially at night 

• Prevent exercise-induced narrowing of the airways (exercise-induced bronchoconstriction) 

• Treat hay fever and allergic rhinitis (both seasonal and year-round) 

• Reduce symptoms like wheezing, sneezing, blocked or runny nose 

Montelukast is not a rescue medicine – it will not help during an asthma attack[1]. 

How does montelukast work?

Montelukast works by blocking chemicals called leukotrienes, which the body releases during allergic reactions. Leukotrienes cause[1]: 

• Airway inflammation and tightening 

• Increased mucus production 

• Sneezing and congestion 

By blocking these effects, montelukast helps keep airways open and reduces allergy symptoms[1]. 

Who can take montelukast?

Montelukast is suitable for adults and children from as young as 6 months (depending on the condition being treated)[1]. 

Use with caution under medical advice if you[1]: 

• Are pregnant or breastfeeding 

• Have a rare hereditary problem of galactose intolerance 

• Are allergic to montelukast 

Please tell your doctor or pharmacist about any conditions you may have or medication you take before you start treatment, and always follow the instructions in the Patient Information Leaflet[2].  

What is the typical dosage of montelukast?

The dosage depends on age and condition[1]: 

• Adults and teens (15+): 10mg tablet once daily 

• Children (6-14 years): 5mg chewable tablet once daily 

• Children (2-5 years): 4mg chewable tablet or granules once daily 

• Children (6 months-2 years): 4mg granules (for year-round allergies only) 

Take the dose exactly as prescribed. Do not take more than one dose in 24 hours. 

How do you take montelukast?

You should take montelukast once daily – in the evening for asthma, or at any time for allergies. It comes in three forms[1]: 

• 10mg Tablets: Swallow whole with water 

• 4mg or 5mg chewable tablets: Chew thoroughly before swallowing 

• 4mg granules: Can be mixed with soft food 

Can you stop taking montelukast?

Do not stop taking montelukast suddenly without medical advice. Stopping it may cause your asthma or allergy symptoms to return. Your doctor may help you gradually reduce your dose if it’s no longer needed[1]. 

What do you do if you take too much montelukast?

If you take too much montelukast, you may experience[1]: 

• Stomach pain 

• Headache 

• Drowsiness 

• Vomiting 

• Hyperactivity 

Contact your doctor or go to A&E if you are worried, especially in children. 

What if you forget to take a dose of montelukast?

If you forget to take your dose[1]: 

• Take it as soon as you remember 

• If it’s nearly time for your next dose, skip the missed one 

• Do not take two doses at once 

What are the side effects of montelukast?

Montelukast is generally safe with most medicines, but caution is needed with[1]: 

• Epilepsy medicine like phenobarbital or phenytoin (may reduce effectiveness) 

• Rifampicin (antibiotic for tuberculosis that lowers montelukast levels) 

• Gemfibrozil (cholesterol medicine that may increase montelukast levels) 

Always inform your doctor or pharmacist about all medications and supplements you take before you start a new medicine, and follow the instructions in the Patient Information Leaflet[2].  

What are the side effects of montelukast?

The most common side effects include[1]: 

• Headache 

• Stomach pain 

• High temperatures 

• A mild rash 

• Nausea or sickness 

• Diarrhoea 

The rarer but more serious side effects include[1]: 

• Mood or behaviour changes (aggression, anxiety, depression, hallucinations) 

• Suicidal thoughts or actions 

• Difficulty concentrating 

• Unusual or fast heartbeat 

• Shaking or trembling 

• Yellowing of skin or eyes 

• New problems with sleep 

• Flu-like symptoms 

• Allergic reactions (rash, swelling, trouble breathing) 

There have also been reports of neuropsychiatric reactions in patients taking montelukast. If you see any signs of this, you should speak to your doctor immediately so that they can carefully consider the benefits and risks of continuing treatment[4]. 

You should contact your GP if you experience any of these symptoms. In rare cases, the medicine may cause a serious allergic reaction (anaphylaxis). You should call 999 or visit A&E immediately if you believe this is happening[1].

Symptoms of anaphylaxis include:  

• Difficulty breathing  

• Tightness in throat and chest  

• Swelling of the tongue or throat  

• Feeling faint or dizzy  

• Blue/grey skin or lips  

• Loss of consciousness 

If you experience any side effects, including those not listed, you are encouraged to report them via the Yellow Card Scheme or contact your doctor, pharmacist, or nurse. This information is intended as a summary for general awareness and does not replace professional medical advice. 

The information provided in the side effects section is not a comprehensive list of all possible side effects associated with this medication. For a complete list of side effects, please refer to the Patient Information Leaflet (PIL) provided with your medication or consult your healthcare professional[2]. 

Frequently asked questions about montelukast

Is montelukast a steroid? 
No, it’s not a steroid. It works by blocking leukotrienes, which cause inflammation[1]. 

Can I take montelukast long-term? 
Yes, many people take it long-term for asthma or allergies under medical supervision[1]. 

Can I drink alcohol while taking montelukast? 
Moderate alcohol is generally safe but speak to your doctor if you have liver problems[1]. 

Does montelukast cause weight gain? 
Weight gain is not a common side effect[1]. 

Can montelukast be used during pregnancy? 
Only if clearly needed – consult your doctor to weigh the risks and benefits[1]. 

For the official NHS guide to montelukast, visit their website.