Montelukast for asthma

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Montelukast for asthma

This leaflet is about the use of montelukast for the prevention of asthma.

Information-Standard-logoThis leaflet has been written for parents and carers about how to use this medicine in children. Our information sometimes differs from that provided by the manufacturers, because their information is usually aimed at adult patients. Please read this leaflet carefully. Keep it somewhere safe so that you can read it again.

Name of drug

Brand name: Singulair®

Why is it important for my child to take this medicine?

Montelukast blocks the effects of chemicals in the body that cause inflammation and narrowing of the airway. Taking montelukast regularly will help to stop your child from having asthma attacks.

What is montelukast available as?

  • Tablets: 10 mg
  • Chewable tablets: 4 mg, 5 mg; these contain small amounts of aspartame (phenylalanine)
  • Granules: 4 mg per sachet

When should I give montelukast?

Montelukast is usually given once each day, this is usually in the evening. 

Give the medicine at about the same time each day so that this becomes part of your child’s daily routine, which will help you to remember.

How much should I give?

Your doctor will work out the amount of montelukast (the dose) that is right for your child. The dose will be shown on the medicine label.

It is important that you follow your doctor’s instructions about how much to give.

How should I give montelukast?


Tablets should be swallowed whole, with a glass of water, juice or milk. Your child should not chew these tablets.You can crush the tablet and mix it with a small amount of soft food such as yogurt, honey or jam. Make sure your child swallows it straight away, without chewing.


Chewable tablets should be chewed or sucked. Your child can have a drink afterwards. They should be taken at least 1 hour before eating or 2 hours after eating.


Granules: Sprinkle or stir the granules into a small amount of cold soft food (e.g. yogurt). Your child should then swallow the food straight away, without chewing. Make sure that they take it all.

  • Do not mix the granules with warm food or liquid.
  • Your child must take the granules within 15 minutes of opening the sachet. If the sachet has been open for more than 15 minutes, throw the contents away and use a new sachet.
  • Do not keep granules or a granule/food mixture to give later.

When should the medicine start working?

Your child may need to take montelukast for a few weeks before it starts to prevent asthma attacks. Continue to give montelukast to your child during this time. Give their other asthma medicines as your doctor has told you to.

What if my child is sick (vomits)?

  • If your child is sick less than 30 minutes after having a dose of montelukast give them the same dose again.
  • If your child is sick more than 30 minutes after having a dose of montelukast, you do not need to give them another dose. Wait until the next normal dose.

If your child is sick again, seek advice from your GP, pharmacist or hospital. They will decide what to do based on your child’s condition and the specific medicine involved.

What if I forget to give it? 

  • If you remember before your child has gone to sleep, give them the missed dose. If you remember after your child has gone to sleep, you do not need to wake them up to give the missed dose. 
  • You can give the missed dose in the morning, as long as this is at least 6 hours before the next evening dose will be given.

Never give a double dose of montelukast.

What if I give too much?

If you give your child too much montelukast, they may get stomach ache, feel or be sick (vomit), get a headache, feel thirsty, and they may be sleepy or more active than normal (especially younger children).

If you think you may have given your child too much montelukast, contact your doctor or local NHS services (111 in England and Scotland; 0845 4647 in Wales) or take your child to hospital. 

Take the medicine container or packaging with you, even if it is empty. This will be useful to the doctor. Have the medicine or packaging with you if you telephone for advice.

Are there any possible side-effects?

We use medicines to make our children better, but sometimes they have other effects that we don’t want (side-effects).

Side-effects that you must do something about

If your child gets swelling of the face, lips or tongue, a skin rash or itching, has difficulty breathing or has a fit (seizure), take them to hospital or call for an ambulance straight away, as they may be allergic to montelukast.

If your child has flu-like symptoms (temperature above 38°C, aches, headache) and also pins and needles, numbness, a rash, and their asthma gets worse, contact your doctor straight away, as they may have a rare syndrome called Churg–Strauss syndrome. This is more likely if the dose of inhaled steroids that your child has (the brown inhaler) has been reduced.

If your child has an irregular or fast heart beat (they may say that their heart feels fluttery or is racing), contact your doctor straight away.

If your child gets a yellowish tinge to the skin or whites of the eyes, contact your doctor straight away, as there may be a problem with your child’s liver.

If your child seems to bruise more easily than usually, or a cut or graze does not stop bleeding as quickly as you would expect, contact your doctor straight away, as there may be a problem with your child’s blood.

Other side-effects you need to know about 

When your child first starts taking montelukast they may have the following side-effects. Most of these wear off as your child gets used to the medicine. If they are still a problem after about 2 weeks, contact your doctor.

  • They may feel or be sick (vomit) and have diarrhoea.
  • They may get headache or muscle pain (myalgia).
  • They may have a dry mouth or feel thirsty. Eating citrus fruits (e.g. oranges) and taking sips of water may help.
  • Your child’s skin may feel itchy. Using a moisturising cream may help.
  • Your child may have nightmares or problems sleeping.
  • Your child may feel tense, nervous or ‘on edge’. Young children (under 5 years of age) may seem more active than usual.
  • Your child may feel light headed or faint. They should try not to stand up too quickly. They should lie down for a while if they feel faint.

There may, sometimes, be other side-effects that are not listed above. If you notice anything unusual and are concerned, contact your doctor. You can report any suspected side-effects to a UK safety scheme at http://www.mhra.gov.uk/yellowcard.

Can other medicines be given at the same time as montelukast?

  • You can give your child medicines that contain paracetamol or ibuprofen, unless your doctor has told you not to.
  • Montelukast should not be given with some medicines that you get on prescription. Tell your doctor and pharmacist about any other medicines your child is taking before starting montelukast.
  • Check with your doctor or pharmacist before giving any other medicines to your child. This includes herbal or complementary medicines.

Is there anything else I need to know about montelukast?

  • Montelukast is used to help prevent asthma attacks. It should not be used to stop an attack that has already started, as it will not help. Use your child’s reliever medicine (the blue inhaler) to help with an attack that has already started.

General advice about medicines

  • Try to give the medicine at about the same time each day, to help you remember.
  • Only give this medicine to your child. Never give it to anyone else, even if their condition appears to be the same, as this could do harm. 

If you think someone else may have taken the medicine by accident, contact your doctor for advice.

  • Make sure that you always have enough medicine. Order a new prescription at least 2 weeks before you will run out.
  • Make sure that the medicine you have at home has not reached the ‘best before’ or ‘use by’ date on the packaging. Give old medicines to your pharmacist to dispose of.

Where should I keep this medicine?

  • Keep the medicine in a cupboard, away from heat and direct sunlight. It does not need to be kept in the fridge. 
  • Keep the medicine in the container it came in.
  • Make sure that children cannot see or reach the medicine.

Who to contact for more information 

Your child’s doctor, pharmacist or asthma practice nurse will be able to give you more information about montelukast and about other medicines used to treat asthma.

You can also get useful information from: 
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