Clarithromycin is an antibiotic.

It’s used to treat chest infections, such as pneumonia, skin problems such as cellulitis, and ear infections. It’s also used to get rid of Helicobacter pylori, a bacteria which can cause stomach ulcers.

Clarithromycin is sometimes used by people who have an allergy to penicillin and antibiotics similar to penicillin, like amoxicillin.

Clarithromycin is only available on prescription. It comes as tablets, granules, or a liquid that you drink. It can also be given by injection, but this is usually only done in hospital.

  • It’s usual to take clarithromycin twice a day, once in the morning and once in the evening.
  • Some people take slow-release clarithromycin tablets. These are taken once a day.
  • For most infections, you should feel better within a few days.
  • The most common side effects of clarithromycin are feeling sick, vomiting, stomach cramps, and diarrhoea.
  • You can drink alcohol while taking clarithromycin.
  • Clarithromcyin is also called by the brand names Clarie XL, Klaricid, Klaricid XL and Xetinin XL.

Clarithromycin can be taken by adults and children.

Clarithromycin isn’t suitable for some people. To make sure clarithromycin is safe for you, tell your doctor if you have:

  • had an allergic reaction to clarithromycin or any other medicines in the past
  • had diarrhoea when you’ve taken antibiotics before
  • fast, pounding or irregular heartbeats
  • abnormally low levels of potassium in your blood
  • liver or kidney problems
  • porphyria (a rare, inherited blood disorder)
  • myasthenia gravis – clarithromycin can make the symptoms of this muscle-weakening illness worse
  • an illness called phenylketonuria – people with phenylketonuria have to avoid the sweetener, aspartame. Some brands of liquid clarithromycin contain aspartame

Also tell your doctor if you’re pregnant, trying to get pregnant, or if you’re breastfeeding. Clarithromycin is not generally recommended during pregnancy and while breastfeeding.

The usual dose of clarithromycin is 250mg to 500mg twice a day.

The dose may be lower for children and if you have kidney problems.

If your doctor prescribes slow release or modified release tablets, the dose is 500mg once a day. These tablets release the medicine slowly, which means that 1 dose a day is enough.

Try to take your medicine at the same time every day.

Like all medicines, clarithromycin can cause side effects, although not everyone gets them.

Common side effects

These common side effects of clarithromycin happen in more than 1 in 100 people.

Keep taking the medicine, but tell your doctor if these side effects bother you or don’t go away:

  • feeling sick
  • vomiting
  • diarrhoea
  • losing your appetite
  • bloating and indigestion
  • headache
  • difficulty sleeping (insomnia)

Serious side effects

Serious side effects are rare and happen in less than 1 in 1,000 people.

Tell a doctor straight away if you get:

  • a faster or irregular heartbeat
  • yellow skin or eyes – this can be a sign of liver problems
  • severe pain in your stomach or back – these can be warning signs of inflammation of the pancreas (pancreatitis)
  • paleness, feeling tired, faint or dizzy, purple spots, blotching on the skin, any sign of bleeding (like bleeding from your gums, bleeding for a long time, bruising more easily, sore throat and fever (a temperature of 38C or more) and getting infections more easily) – these can be signs of blood or bone marrow disorder
  • severe diarrhoea with blood in your poo
  • hallucinations (seeing or hearing things that aren’t there)
  • ringing in your ears, hearing loss, or feeling unsteady on your feet

Serious allergic reaction

In rare cases, it’s possible to have a serious allergic reaction to clarithromycin.

What to do about:

  • feeling sick – stick to simple meals and don’t eat rich or spicy food while you’re taking this medicine. It might help to take your clarithromycin after you’ve had a meal or snack.
  • diarrhoea and vomiting – drink plenty of water or other fluids if you have diarrhoea or you’re vomiting. It may also help to take oral rehydration solutions you can buy from a pharmacy to stop dehydration. Don’t take any other medicines to treat diarrhoea or vomiting without speaking to a pharmacist or doctor.
  • losing your appetite – eat when you would usually expect to be hungry. If it helps, eat smaller meals more often than usual. Snack when you’re hungry. Have nutritious snacks that are high in calories and protein, such as dried fruit and nuts.
  • bloating and indigestion – try not to eat foods that cause wind (like pulses, lentils, beans and onions). Eat smaller meals, eat and drink slowly, and exercise regularly. There are pharmacy medicines that can also help, such as charcoal tablets or simethicone.
  • headache – rest and drink plenty of fluids. Don’t drink too much alcohol. Ask your pharmacist to recommend a painkiller if you need one. Talk to your doctor if the headaches last longer than a week or are severe.
  • difficulty sleeping (insomnia) – avoid having a big meal, smoking, drinking alcohol, tea or coffee in the evening. Try not to watch television or use your mobile phone before going to bed. Instead, try and relax for an hour before bedtime.

Clarithromycin is not normally recommended during pregnancy and while breastfeeding. But your doctor may prescribe it if the benefits of you taking it are greater than the risks.

Erythromycin is the antibiotic most often used in pregnancy.

There are some medicines that don’t mix well with clarithromycin.

Tell your doctor if you’re taking these medicines before you start clarithromycin:

  • ergotamine and dihydroergotamine used to treat migraines
  • medicines for epilepsy, such as carbamazepine and phenytoin
  • theophylline for asthma
  • colchicine for gout
  • digoxin – for some heart problems
  • warfarin – to thin blood or prevent blood clots
  • a statin medicine to lower your cholesterol – such as simvastatin and atorvastatin

Mixing clarithromycin with herbal remedies and supplements

There are no known problems with taking herbal remedies or supplements alongside clarithromycin.

However, for safety, speak to your pharmacist before taking clarithromycin if you take any herbal or alternative remedies.

How does clarithromycin work?