Carbocisteine: uses, side effects and cautions

In chronic obstructive pulmonary disease (COPD) and cystic fibrosis the airways can produce more phlegm than usual, and it becomes thick and sticky, difficult to cough up. Carbocisteine is a mucolytic medicine that makes it less sticky. The NHS says it starts working straight away, although it can take a while to notice that symptoms are better, because phlegm needs time to break up.

It is a symptom treatment for mucus, not an inhaler and not a bronchodilator, so it is used alongside whatever breathing treatment you already have.

Carbocisteine usually comes as 375 mg capsules. A liquid or syrup, with 250 mg in each 5 ml, suits children and people who struggle to swallow capsules, and there are 750 mg sachets of liquid. Some solutions contain alcohol and are only for adults.

The NHS gives the usual adult dose as two 375 mg capsules three times a day, which a doctor may reduce to one capsule four times a day once symptoms improve. For syrup or bottle liquid it is 15 ml three times a day, possibly reduced to 10 ml, and for sachets one sachet three times a day, possibly twice a day later.

For children, the NHS gives 1.25 to 2.5 ml four times a day at ages 2 to 4, 5 ml three times a day at ages 5 to 11, and 15 ml three times a day at 12 to 17. Always measure liquid with the syringe or spoon supplied, not a kitchen teaspoon, and follow your own prescription.

Swallow capsules whole. You can take it with food or without. If you forget a dose, take it as soon as you remember unless the next is due in under 2 hours, in which case skip it. Never take two doses together or an extra one to catch up.

Taking too much is unlikely to harm you or your child and usually causes no symptoms. If you have an upset stomach or are vomiting after too much, call NHS 111, and use 111 for any child under 5.

The NHS says diarrhoea and feeling sick can happen in 1 in 10 people. For diarrhoea, drink plenty of fluids and check with a pharmacist before using anything to stop it; severe diarrhoea lasting more than 24 hours can make contraceptive pills less reliable. For nausea, simple meals and taking the medicine after eating may help.

Serious effects are rare. Call 111 for advice if you vomit blood or your stools are black and tarry, which can point to bleeding in the stomach or gut. Swelling of the lips, mouth, throat or tongue can signal an allergic reaction and needs 999. Suspected side effects can be reported through the Yellow Card scheme.

Most adults and children from 2 years can take carbocisteine. Tell your doctor if you have ever had an allergic reaction to it or another medicine, if you have ever had a stomach ulcer, or if you are pregnant, planning pregnancy or breastfeeding.

The NHS asks you to mention medicines that can cause bleeding or ulcers in the stomach, since the combination could add to the risk. These include NSAIDs such as ibuprofen, naproxen, diclofenac or high-dose aspirin, steroids, and antiplatelet medicines such as clopidogrel, low-dose aspirin and ticagrelor.

The NHS says carbocisteine is not generally recommended in the first trimester because there is very little information on whether it might affect development, and a doctor may suggest an alternative depending on why a mucolytic is needed. If your doctor or health visitor says your baby is healthy, it is usually fine while breastfeeding, though it is unknown how much reaches the milk, and other treatments with more breastfeeding data may be preferred. There is no evidence of an effect on fertility.

Carbocisteine does not stop any contraceptive working. You can drive, cycle, drink alcohol and eat normally. The NHS says there is no evidence it is harmful when taken for a long time.

Alternatives named by the NHS include erdosteine, an oral mucolytic usually given for a short time if chronic bronchitis is getting worse, and dornase alfa and mannitol, which are only for cystic fibrosis and are given by inhaler or nebuliser.