Montelukast

Your GP or nurse may prescribe you a medicine called montelukast if you’re still getting asthma symptoms even though you’ve been taking your usual asthma medicines as prescribed.

Montelukast is an add-on treatment. This means you take montelukast as prescribed, as well as using your maintenance or preventer inhaler.

Montelukast is one of a group of medicines called leukotriene receptor antagonists. It's also known by the brand Singulair. It comes as a tablet or granules.

If you get asthma symptoms or have an asthma attack, you still need to use your reliever inhaler.

Most adults and children aged at least six months old can take montelukast.

Before taking montelukast, tell your GP if you: 

• have had an allergic reaction to any medicines before
• are pregnant or breastfeeding
• have a rare hereditary problem called galactose intolerance.

You should also tell your GP, nurse or pharmacist if you, or your child, has a common mental health condition, like depression or anxiety.

This is because there are rare, but serious, side effects from montelukast related to mental health.

If montelukast is a new medicine for you, your GP, nurse or other healthcare professional should check how you're getting on with it after eight to twelve weeks.

Montelukast helps prevent asthma symptoms like swelling and inflammation in your airways.

It may also help you if your asthma is triggered by exercise or by seasonal allergies.

Montelukast can help your asthma by:

• making it easier for you to breathe
• preventing asthma attacks
• stopping your airways from narrowing when you exercise
• improving symptoms of seasonal allergies, like hay fever.

“Side effects from montelukast relating to mood and behaviour can affect people of all ages including children and young adults. It’s important to seek help and advice as soon as you notice any changes. Call your GP or 111 straight away. Your GP can support you in changing medicines safely and keeping your asthma under control.” 

Dr Andy Whittamore, Asthma + Lung UK’s GP 

Like all medicines, montelukast can cause side effects in some people, but not everyone gets them.

If you, or your child, have been prescribed montelukast it’s important to know about some of the more serious side effects, although these are much less common.

The patient information leaflet inside your medicine packet will list all the possible side effects. Always read this carefully and speak to your GP, nurse or pharmacist if you have any concerns.

Common side effects

Common side effects affecting up to 1 in 10 people include stomach pain, diarrhoea, headache, a mild rash, a high temperature, and feeling sick. The NHS has advice on how to manage common side effects. 

Serious side effects

There have been reports of less common but more serious side effects from taking montelukast.

These include changes in mood and behaviour which can affect 1 in 100 people.

Speak to your GP urgently or call 111 as soon as possible, if you notice any of these signs or symptoms:

• changes to your mood or behaviour, or your child's behaviour
• new or worsening problems sleeping, including nightmares
• new, or worsening feelings of aggression, anxiety or depression
• difficulty concentrating or remembering things
• asthma symptoms getting worse
• shaking or trembling
• an unusual or fast heartbeat
• speech changes or stuttering
• a combination of symptoms including flu-like symptoms, and pins and needles
• numbness in your arms or legs, or a rash
• the whites of your eyes turn yellow, although this may be less obvious on brown or black skin.

Very rare side effects (affecting around 1 in 10,000 people) include:

• hallucination (seeing things which are not there)
• suicidal thoughts

Report any side effects to the Yellow Card Scheme 

If you notice any side effects from taking montelukast, it's quick and easy to report them to the Yellow Card scheme.

Anyone can report side effects to the Yellow Card scheme, and it can make a big difference to other people using the same medicine as you.

Always follow your doctor’s instructions about how and when to take montelukast. Most people take montelukast once a day in the evening.

If exercise makes your asthma worse, your doctor might tell you to take montelukast two hours before you exercise.

• Non-chewable tablets are for adults and young people aged 15 and over. 
• Chewable tablets come in two doses, for children aged 6 to 14 and children aged 2 to 5. You or your child should take chewable tablets at least one hour before food or two hours after food.
• Granules are for young children who cannot take chewable tablets. You can put them directly on your child's tongue or mix them with a spoonful of cold, soft food such as yoghurt. Do not dissolve them in a drink.

If you miss a dose

If you miss a dose of montelukast, take it the next day at the usual time. Do not take two doses to make up for the one you forgot.