A macrolide antibiotic
Clarithromycin
A macrolide antibiotic often used when penicillin cannot be — effective for chest and other infections, but with many drug interactions to watch.
What is Clarithromycin?
Clarithromycin is a macrolide antibiotic used for chest, ear, sinus and throat infections, some skin infections, and as part of combination treatment to clear stomach ulcer bacteria. It is often chosen for people who cannot take penicillin.
Education and reference only. This is a plain-language guide to Clarithromycin — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Clarithromycin is a macrolide antibiotic used for chest infections, ear, sinus and throat infections, some skin infections, and as part of combination treatment for stomach-ulcer bacteria (Helicobacter pylori). It is a common alternative for people who are allergic to penicillin, because it is from a different family. It is taken as a short course and works against bacteria, not viruses.
How it works
Clarithromycin gets inside bacteria and blocks the machinery they use to make proteins, so the bacteria cannot grow and multiply and the infection is brought under control. Because it is not a penicillin, it can be used in many people who are penicillin-allergic. However, it is processed by the same liver pathways that handle many other medicines, which is why it has a long list of important drug interactions.
Company & origin
Originated / developed by: Taisho Pharmaceutical (Japan); licensed to Abbott Laboratories.
Clarithromycin is a macrolide antibiotic invented by scientists at Taisho Pharmaceutical in Japan, who filed for patent protection around 1980. International rights were licensed to Abbott Laboratories, which gained US FDA approval (as Biaxin) in October 1991; it is marketed in the UK as Klaricid.
Practical use
How to take Clarithromycin
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it as prescribed and finish the whole course, even if you start to feel better.
- Can usually be taken with or without food; taking it with food may ease stomach upset.
- Space the doses evenly through the day for steady levels.
- Tell your prescriber and pharmacist about your other medicines, including statins, as clarithromycin can interact with several drugs.
- If you miss a dose, take it when you remember unless the next one is close, then continue; do not double up.
Weighing it up
Advantages & disadvantages of Clarithromycin
Advantages
- A useful alternative for people who are allergic to penicillin.
- Covers a range of respiratory, ear, throat and skin infections.
- Part of standard combination treatment to eradicate stomach ulcer bacteria.
- Taken by mouth, generally twice a day.
Disadvantages
- Interacts with many other medicines, including some statins and heart drugs.
- Can cause an altered or metallic taste, nausea and stomach upset.
- May rarely affect heart rhythm, particularly alongside other interacting medicines.
- Contributes to antibiotic resistance if overused.
Practical use
Good to know
The headline issue with clarithromycin is interactions. It can raise the levels of several common medicines, including statins — where it increases the risk of muscle harm — and it affects warfarin and many others, so statins are often paused during a course and other medicines reviewed. It can also affect the heart's electrical rhythm (QT prolongation), so care is needed in people with heart-rhythm risks or taking other medicines that do the same. A metallic or bitter taste is a common, harmless nuisance. As with all antibiotics, take it exactly as prescribed and finish the course as advised, using it only when truly needed — part of antimicrobial stewardship.
Who should not take it / use with caution
- People taking certain medicines it must not be combined with (including some statins and certain heart, migraine and other drugs) — always have your medicines reviewed first.
- People with certain heart-rhythm problems (a long QT interval) or significant electrolyte disturbances, where it is used with caution or avoided.
- People who have had an allergic reaction to a macrolide antibiotic; used with care in significant liver or kidney problems.
Monitoring
- Whether the infection is improving
- A medicines review for interactions before and during the course (statins, warfarin and others)
- For heart-rhythm symptoms or signs of allergy
Side effects
- A metallic or bitter taste, feeling sick, stomach upset or loose stools — common and usually mild.
- Headache, and occasionally a disturbed sense of taste or smell.
- Less commonly, effects on the heart rhythm (QT prolongation), liver upset, or a serious allergic reaction (call 999 for swelling of the face or throat, wheeze or collapse); report a fast or irregular heartbeat or fainting.
Key interactions
- It can sharply raise the levels of some statins (such as simvastatin and atorvastatin), increasing the risk of muscle harm — statins are often paused during a course.
- It increases the effect of warfarin (more bleeding risk) and interacts with many other medicines processed by the liver, including some heart, epilepsy and migraine drugs.
- It can add to the heart-rhythm (QT) effect of other medicines; always have your full medicines list checked before starting.
Available as: Tablets and an oral suspension (liquid) for those who cannot swallow tablets; also given by injection in hospital.
Answers
Clarithromycin: frequently asked questions
Why has my statin been paused while I take clarithromycin?
Clarithromycin can raise the level of some statins in the blood, which increases the risk of muscle problems. To stay safe, prescribers often pause the statin for the few days of the antibiotic course and restart it afterwards. Missing a few doses of a statin does not undo its long-term benefit.
Why does clarithromycin have so many interactions?
It is handled by the same liver pathways that process many other medicines, so it can raise or lower their levels. This is why it is important to give your pharmacist or prescriber a full list of everything you take — including over-the-counter and herbal products — before starting it.
It is leaving a strange taste in my mouth — is that normal?
Yes. A metallic or bitter taste is a common and harmless side effect of clarithromycin and usually goes once the course is finished. Let your pharmacist know if it is troublesome, but it is not a reason to stop unless you are advised to.
Can I take clarithromycin if I am allergic to penicillin?
Often yes — clarithromycin is a macrolide, a different family from penicillin, so it is a common choice when someone is penicillin-allergic. Tell your prescriber about any antibiotic allergies so the safest option is chosen for you.
What is the difference between clarithromycin and Klaricid?
They are the same medicine — clarithromycin is the generic (active-ingredient) name and Klaricid is a brand name. Generic clarithromycin contains the identical active ingredient.
The wider class
About Macrolide antibiotics
Clarithromycin belongs to the macrolide antibiotics class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF: Clarithromycin.
- electronic Medicines Compendium (SmPC): Clarithromycin (Klaricid).
- NICE CKS: Clarithromycin.
- NICE: Antimicrobial stewardship.
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