Leukotriene Receptor Antagonists (LTRAs)

If your asthma symptoms are not well controlled with a preventer inhaler your GP may prescribe a Leukotriene Receptor Antagonist (such as Montelukast) for some extra help.

What are Leukotriene Receptor Antagonists? 

Three ways LTRAs help with asthma

What types of LTRAs are there?

Are LTRAs suitable for everyone?

What kind of benefits can you expect – and when?

Possible side effects of LTRAs – including Montelukast

Get the best from your LTRAs

What are Leukotriene Receptor Antagonists?

Leukotriene Receptor Antagonists (LTRAs) are an 'add-on' treatment. They come in tablet form for adults or granules for children. They're sometimes called preventer tablets. But they are not steroid based like your preventer inhaler.

NICE guidelines recommend your doctor prescribes an LTRA if you've been taking your preventer inhaler 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," says Dr Andy Whittamore, Asthma UK's in house GP. "This means you need to carry on taking your usual preventer medicine as well as taking your LTRA tablets as prescribed."

Three ways LTRAs help with asthma

1. LTRAs help deal with symptoms during the day and the night

"They calm the inflammation in your airways," says Dr Andy. "This 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.

2. 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.

3. 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 LTRAs 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.  

Zafirlukast – now discontinued

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

  • Zafirlukast is no longer 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.

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. NICE now recommends doctors prescribe LTRAs earlier on for people still getting asthma symptoms even though they’re taking their preventer medicines regularly.


  • If you suddenly stop taking LTRAs, your asthma symptoms may return, which could lead to an asthma attack.
  • If your asthma improves with this medicine, don’t be tempted to stop taking any of your other asthma 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.

Possible side effects of LTRAs

Like all medicines, LTRAs can cause side effects because everyone has their own individual responses to treatments. LTRAs work very well for many people with asthma. The important thing to remember is that a medicine is only ever available and recommended by NICE if clinical trials have shown that the benefits of taking it outweigh the risks. 

“But a small number of people can experience side effects,” says Dr Andy. “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.”

It’s important to talk to your GP or asthma nurse if you notice any of the following things, so you can take actions to reduce or prevent the side effects or find a medicine that suits you better.

  • Around 1 in 10 to 1 in 100 people taking LTRAs often have sore throats and infections. That also means 9 out of 10 to 99 out of 100 people who take them won’t get these side effects.

  • There have been reports of people taking montelukast having mental health issues due to the medicine. “These are not common,” says Dr Andy. “We are highlighting them to put your mind at rest about what to look out for and what to do,  because there can be a lot of talk on forums and in the media.”

    Sleep issues such as insomnia, nightmares or sleepwalking and mood disorders such as anxiety, depression and irritability affect between 1 in 100 to 1 in 1000 people. “If you or your child notice these changes, talk to your GP as soon as possible,” says Dr Andy.

    There is also a very rare potential side effect of suicidal thinking, that affects fewer than 1 in 10,000 people. “This is extremely rare, but it has happened and is very distressing in those cases,” says Dr Andy. “If you do get this side effect, stop taking the medicine immediately and talk to your GP or asthma nurse as soon as possible.”

    “It is important to make sure you have the right asthma medicine to replace it so you’re not left open to an asthma attack, and also to rule out any other causes of the mental health issues which may need support.“

  • In very rare cases LTRAs might affect your ability to drive or operate machinery. That means fewer than one person in every 10,000 people. 

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 do get a serious side effect from a medicine it should be reported. You can do it or so can your healthcare professional,” says Dr Andy. 

We also have a useful Q&A about the common concerns you might have about taking asthma medicines here

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.

“If you have been taking montelukast or another LTRA and it is suiting you but not working as well as you had hoped, speak with your GP or asthma nurse,” says Dr Andy.

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 June 2019

Next review due April 2021

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