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.
Who can and can't take clarithromycin
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.
How and when to take
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.
How to take it
Clarithromycin tablets come in 250mg or 500mg strengths. Swallow clarithromycin tablets or capsules whole with a drink of water, with or without food. Don't chew or break them.
Clarithromycin granules come in 250mg sachets. Open the pack – or packets – and mix the granules with a small amount of water to drink.
There's also a liquid clarithromycin for children and people who find it difficult to swallow tablets.
If you or your child are taking clarithromycin as a liquid, your pharmacist will usually make it up for you. The medicine will come with a plastic syringe or spoon to help you take the right amount. If you don't have a syringe or spoon, ask your pharmacist for one.
What if I forget to take it?
If you forget to take a dose, take it as soon as you remember, unless it's nearly time for your next dose. In this case, just leave out the missed dose and take your next dose as normal.
Never take 2 doses at the same time. Never take an extra dose to make up for a forgotten one.
If you often forget doses, it may help to set an alarm to remind you. You could also ask your pharmacist for other ways to remember your medicine.
What if I take too much?
Taking an extra dose of clarithromycin by accident is unlikely to harm you or your child. It may give you temporary side effects, like stomach pain, feeling sick, vomiting, and diarrhoea.
Talk to your pharmacist or doctor if you're worried or get severe side effects, or if you or your child accidentally take more than one extra dose.
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
- losing your appetite
- bloating and indigestion
- 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 an allergic reaction to clarithromycin.
A serious allergic reaction is an emergency. Contact a doctor straight away if you think you or someone around you is having a serious allergic reaction.
The warning signs of a serious allergic reaction are:
- a skin rash that may include itchy, red, swollen, blistered or peeling skin
- tightness in the chest or throat
- having trouble breathing or talking
- unusual hoarseness
- swelling of the mouth, face, lips, tongue, or throat
These are not all the side effects of clarithromycin. For a full list see the leaflet inside your medicine packet.
You can report any suspected side effect to the UK safety scheme.
How to cope with side effects
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.
Pregnancy and breastfeeding
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.
Cautions with other medicines
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?
When will I feel better?
What if I don't get better?
How does clarithromycin compare with other antibiotics?
Can I drink alcohol with it?
Will it give me thrush?
Will it stop my contraception working?
Will it reduce my fertility?
Is there any food or drink I need to avoid?