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Mucus (sputum) is made in your lungs. Mucolytics are medicines that make the mucus less thick and sticky and easier to cough up. They are usually prescribed for people who have a long-term (chronic) cough. They work best if they are taken regularly.

Mucus (sputum) is made in your lungs. Mucolytics are medicines that make the mucus less thick and sticky and easier to cough up. They are helpful if you have a long-term (chronic) cough because they help you cough up mucus from your lungs. You may also see the term 'expectorant' used to describe a type of cough medicine. Expectorants reduce the thickness or stickiness of mucus so it can be removed from the lung more easily by coughing. Mucolytics work by breaking down the structure of the molecules that form mucus.

There are a number of mucolytics available to prescribe in the UK. These include carbocisteine and erdosteine. Both are available as capsules. Carbocisteine is also available as an oral liquid. Two other types of mucolytic are available to prescribe. They are called dornase alfa and mannitol. These medicines are inhaled but are usually only prescribed for people with cystic fibrosis.

What else can I do about my cough?

This leaflet is about mucolytics. If you have a cough for more than three weeks you should see your doctor. Treatment will depend on the cause.

Some people need help with a long-term cough for which no cause can be found. A steamy shower or steam from a humidifier can help to loosen phlegm. Simple linctus and cough sweets can be quite soothing. Cough suppressant medicines may help, especially if you have a cough at night, but these usually contain codeine, which can cause constipation if taken excessively.

For more information, see the separate leaflet called Chronic Persistent Cough in Adults.

The mucus (sputum) in your lungs is held together by certain bonds. Mucolytics work by breaking these bonds. When these bonds are broken, the mucus becomes less sticky and less thick, and is easier to cough up. This may also have a knock-on effect of making it harder for germs (bacteria) to infect the mucus and cause chest infections.

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They are normally prescribed for people with a long-term (chronic) productive cough. If you have a productive cough, your lungs make a lot of mucus (sputum) and you cough this up. Examples of people who may have a chronic productive cough include people with chronic obstructive pulmonary disease (COPD) and people with cystic fibrosis.

If you have COPD, they are most likely to help if you have moderate or severe COPD and have frequent or bad flare-ups (exacerbations). The number of flare-ups of symptoms tends to be less in people who take a mucolytic.

Dornase alfa is usually only prescribed for people with cystic fibrosis who have a reduced lung capacity. It helps to make it easier to cough up thick mucus, and is thought to improve how well the lungs work. It also limits any further damage to the lungs. This medicine is usually started by a doctor who specialises in treating patients with cystic fibrosis. Mannitol is an alternative for people with cystic fibrosis who can't take dornase alpha.

Mucolytics work best when they are taken regularly.

Carbocisteine and erdosteine are usually taken twice a day by adults. Your doctor may stop these medicines if you have taken them for one month and they don't seem to be helping your symptoms. Children may need to take these medicines three or four times a day.

Dornase alfa is taken by breathing it into the lungs once or twice a day, using a machine called a nebuliser. Mannitol is taken by breathing it in from a hand-held inhaler. 

Side-effects of treatment with mucolytics occur only rarely but some people have reported bleeding from the gut (gastrointestinal tract) - this is rare. If you develop black stools (faeces), stop taking carbocisteine or erdosteine and let your doctor know as soon as possible. Black stools are a sign of bleeding from the gut.

Most people are able to take a mucolytic; however, they should not be used in people who have a stomach ulcer.

No, they require a prescription.

How to use the Yellow Card Scheme

If you think you have had a side-effect to one of your medicines you can report this on the Yellow Card Scheme. You can do this online at

The Yellow Card Scheme is used to make pharmacists, doctors and nurses aware of any new side-effects that medicines or any other healthcare products may have caused. If you wish to report a side-effect, you will need to provide basic information about:

  • The side-effect.
  • The name of the medicine which you think caused it.
  • The person who had the side-effect.
  • Your contact details as the reporter of the side-effect.

It is helpful if you have your medication - and/or the leaflet that came with it - with you while you fill out the report.

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Further reading and references