Clarithromycin !
A macrolide used against H. pylori, chest infections and Mycobacterium avium. It strongly blocks CYP3A, so it has many drug interactions.
Updated 2026-11-01
The figure shows clarithromycin bound to the 50S ribosomal subunit of Mycobacterium tuberculosis, a relative of M. avium, which clarithromycin treats.
Mechanism of action
Clarithromycin binds the 23S rRNA in the exit tunnel of the 50S subunit and halts protein synthesis. It is more acid-stable and better absorbed than erythromycin, and its 14-hydroxy metabolite is also active. It is a strong CYP3A inhibitor, which raises the levels of many drugs.
- Absorbed by mouth and partly converted to an active metabolite
- Binds the 23S rRNA of the 50S subunit
- The exit tunnel is blocked
- Protein synthesis halts and growth stops
Pharmacokinetics
- Absorption
- Oral bioavailability about 50%; food does not change the amount absorbed.
- Metabolism
- Liver, by CYP3A, to the active 14-hydroxy metabolite; it also inhibits CYP3A.
- Elimination
- Urine and faeces; the dose is adjusted in moderate or severe kidney impairment.
- Half-life
- About 3–7 hours, longer at higher doses.
Indications
- Helicobacter pylori eradication, combined with a proton-pump inhibitor and amoxicillin Helicobacter pylori gastritis →
- Community-acquired pneumonia and other respiratory infections Community-acquired pneumonia →
- Streptococcal pharyngitis when a β-lactam cannot be used Streptococcal pharyngitis →
- Prevention and treatment of Mycobacterium avium complex disease in advanced HIV infection
Adverse effects
Common
- Altered or metallic taste
- Diarrhoea, nausea and abdominal pain
- Headache
Contraindications
- Allergy to any macrolide
- Use with cisapride, pimozide, ergot alkaloids, lomitapide, lovastatin, simvastatin or lurasidone
- Colchicine in patients with kidney or liver impairment
- Previous cholestatic jaundice with clarithromycin; QT prolongation or ventricular arrhythmia
Key interactions
- Simvastatin and lovastatin
- Contraindicated: risk of rhabdomyolysis.
- Colchicine
- Life-threatening colchicine toxicity, especially with kidney or liver impairment.
- Carbamazepine, ciclosporin, tacrolimus and other CYP3A substrates
- Levels rise; drug levels are monitored.
- Warfarin
- Stronger anticoagulant effect.
What is monitored
- Full medication review before starting, for CYP3A interactions
- ECG if there is QT risk
- INR on warfarin; liver tests if symptoms
Administration and safety
- Extended-release tablets are swallowed whole
- Check every other medicine the patient takes before the first dose
Nursing care
- Look for statins, colchicine, antiarrhythmics and transplant drugs on the medication list
- Warn about a bitter or metallic taste
- Teach to report palpitations, muscle pain, dark urine or yellow skin
Pregnancy and breastfeeding
Not recommended in pregnancy unless no suitable alternative exists, because of findings in animal studies.
Test yourself
Think of the answer, then tap the question to see it.
Why is simvastatin contraindicated with clarithromycin?
Clarithromycin blocks CYP3A, raising simvastatin levels and the risk of rhabdomyolysis.
In which infection is clarithromycin part of triple therapy?
Helicobacter pylori, with a proton-pump inhibitor and amoxicillin.
Which mycobacterium does clarithromycin treat?
Mycobacterium avium complex, mainly in advanced HIV infection.
Related drugs
Related conditions
← Back to the class: Macrolides
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - CLARITHROMYCIN tablet, film coated (DailyMed (U.S. National Library of Medicine), 2026); Clarithromycin: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); eEML - Electronic Essential Medicines List (World Health Organization, 2025).
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Representative model, for educational purposes only.