Leukotriene Receptor Antagonists (LTRAs)

If your asthma symptoms are not well controlled with a preventer inhaler alone your GP may prescribe a Leukotriene Receptor Antagonist for some extra help.

What are Leukotriene Receptor Antagonists?

Leukotriene Receptor Antagonists (LTRAs) are an 'add-on' treatment. They come in tablet form and are sometimes called preventer tablets. Unlike your preventer inhaler the LTRA medicine is not steroid based.

You may be prescribed an LTRA if you've been taking your preventer inhaler as prescribed, and in the right way, but you're still having symptoms, and still needing to use your reliever inhaler three or more times a week.

It’s important to remember that LTRAs are an ‘add on’ treatment. This means you need to carry on taking your usual preventer medicine as well as taking your LTRA tablet as prescribed. 

How do LTRAs help with asthma?

Alongside your preventer inhaler the LTRA preventer tablet will give you some extra help to deal with your asthma symptoms.

LTRAs calm the inflammation in your airways

This helps deal with symptoms during the day and during the night. It makes it easier to breathe and helps prevent asthma attacks.

In one 12-week trial of patients aged two to five, those taking LTRAs had more days without any asthma symptoms and needed lower doses of inhaled steroids.

In another clinical trial carried out in adults, LTRAs reduced symptoms and lowered the need for higher doses of inhaled steroids.

LTRAs reduce your body's response to allergens

LTRAs can help with allergies. This is because LTRAs block the effects of chemicals in your body called 'leukotrienes'.

During an allergic reaction your body releases leukotrienes. These chemicals cause your airways to become inflamed. So, if you have hay fever as well as asthma, your GP or asthma nurse may prescribe you LTRAs.

Blocking the effects of these chemicals stops the inflammation and swelling in your airways. And this also improves your asthma symptoms and reduces the risk of a potentially fatal asthma attack.

LTRAs can help people with exercise-induced asthma

LTRAs can help people who have symptoms of asthma only when they exercise and not at any other times. This is because they have ‘exercise-induced asthma’, which is quite a rare specific type of asthma. 

When we exercise we take more cold air in through our mouths. LTRAs help cut down how sensitive your airways are to cold air.

LTRAs have been shown to improve lung function, reduce symptoms, and reduce the use of reliever medicine.

They’ve also been shown to increase physical activity and improve quality of life.

What types of LTRA are there?


The most common type of LTRA is Montelukast (sometimes called by the brand name Singulair).

Montelukast is available as tablets to swallow with water for adults and children over 15. It’s also available as chewable tablets for children aged 2 to 14.

Younger children, or children who are unable to take inhaled preventer medicines, may be prescribed Montelukast as granules, to help prevent asthma symptoms.

These can either be sprinkled directly into the child’s mouth, or placed on a spoonful of cold, or room temperature, food for example pureed fruit or yogurt.

Montelukast is taken at night, either one hour before, or two hours after food.  


Children aged 12 and over, and adults may have been prescribed Zafirlukast (sometimes called by the brand name Accolate).

Zafirlukast comes as tablets which you need to take with water. You should take these 'on an empty stomach', which means you need to take them about an hour before a meal or wait for two hours after eating.

This is because your body absorbs less Zafirlukast after a meal, which means the medicine is less effective.

Zafirlukast will no longer be prescribed (as of March 2018) because it has been discontinued for commercial reasons.

If you’re currently taking it, see your GP for an asthma review to talk about suitable alternatives.

Are LTRAs suitable for everyone?

It’s very important that your GP or asthma nurse knows your full medical history because LTRAs are not suitable for everyone.

For example, LTRAs are not suitable for some people with certain health conditions or for people taking some other kinds of medicines. 

Tell your GP or asthma nurse if you're pregnant or planning to get pregnant. If you’re pregnant and already taking LTRAs the advice is to continue with them. 

But if you’re pregnant and you haven’t started taking LTRAs, your GP will consider alternatives.

Zafirlukast is not recommended if you’re breastfeeding.

Also, over time, it’s possible that LTRAs can become unsuitable for some people even if they have been suitable in the past. 

If you think that taking LTRAs is making you feel unwell, speak to your GP or asthma nurse straight away. They may be able to change the dose. Or they may need to change your prescription.

What kind of benefits can you expect – and when?

It can take one or two weeks before you feel the full benefits of LTRAs, so don’t give up on them too soon. If you're having any problems, it's important to speak to your GP or asthma nurse.


  • If you suddenly stop taking LTRAs, your asthma symptoms may return, which could lead to an asthma attack.
  • If you find that your asthma improves after you start taking this medicine, don’t be tempted to stop taking any of your other medicines. It will cause your symptoms to get worse again.
  • If LTRAs have had no effect after you've been taking them for six weeks, then they are probably not the right medicine for you.
  • Whenever your GP prescribes a new medicine you should have an appointment after four to eight weeks to talk about how you're getting on with the new medicines. If you need to you can talk to your GP about other treatment options.

Possible side effects of LTRAs

Like all medicines, LTRAs can cause side effects. Often side effects can get less, or go, after two to three weeks so it’s worth giving any new medicine a good try first.

  • The most common side effects of LTRAs are frequent sore throats and infections.
  • In very rare cases, LTRAs might affect your ability to drive or operate machinery. 
  • For children who take LTRAs, side effects can also include vomiting, irritability, and nightmares.
  • There have been reports of people taking montelukast having suicidal thoughts. This is extremely rare. If you do get this side effect stop taking the medicine immediately and talk to your GP or asthma nurse.   

Always read the patient information leaflet so you’re aware of what side effects to look out for, and when you need to go straight back to your GP.

If you (or your child) get any side effects speak to your GP, asthma nurse or pharmacist as soon as possible. You may find that there are some simple things you can do to help prevent or reduce these side effects.

The important thing to remember is that a medicine is only ever available if clinical trials have shown that the benefits of taking it outweigh the risks.

You can also read questions and answers about  common concerns you might have about taking asthma medicines.

Get the best from your LTRAs

It is very important that you take LTRAs exactly as they're prescribed. If you don't, you may not get all the benefits.

Make sure you book an asthma review for you or your child at least once a year so your GP or asthma nurse can check how you're doing, and review the medicines you’re taking for your asthma.

Last updated April 2018

Next review due April 2021