[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Macrolides](https://durgical.com/en/pharmacology/classes/macrolides/) › Clarithromycin

[Pharmacology](https://durgical.com/en/pharmacology/) · [Macrolides](https://durgical.com/en/pharmacology/classes/macrolides/)

# 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

- Class: [Macrolides](https://durgical.com/en/pharmacology/classes/macrolides/)
- Target: Bacterial ribosome, 50S subunit (23S rRNA, exit tunnel)
- ATC code: J01FA09
- WHO Model List of Essential Medicines

◆**Bacterial ribosome, 50S subunit (23S rRNA, exit tunnel)**Clarithromycin

ⓘ The figure shows clarithromycin bound to the 50S ribosomal subunit of Mycobacterium tuberculosis, a relative of M. avium, which clarithromycin treats.

**Target in 3D:** Bacterial ribosome, 50S subunit (23S rRNA, exit tunnel). PDB structure 7F0D (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/7F0D) · Drag to rotate · pinch to zoom

## 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 →](https://durgical.com/en/conditions/helicobacter-pylori-gastritis/)
- Community-acquired pneumonia and other respiratory infections [Community-acquired pneumonia →](https://durgical.com/en/conditions/community-acquired-pneumonia/)
- Streptococcal pharyngitis when a β-lactam cannot be used [Streptococcal pharyngitis →](https://durgical.com/en/conditions/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

### Serious (rare, important)

- QT prolongation and ventricular arrhythmias
- Hepatotoxicity
- Serious drug interactions through CYP3A (colchicine toxicity, rhabdomyolysis with statins, hypotension with calcium-channel blockers)
- Higher long-term all-cause mortality seen in a trial in coronary artery disease; C. difficile colitis

## 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.

## Memory aid

«Clari clogs the CYP»: wherever clarithromycin goes, CYP3A slows down and other drugs pile up.

## 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.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/clarithromycin/)

## Related drugs

- [Azithromycin](https://durgical.com/en/pharmacology/azithromycin/)
- [Erythromycin](https://durgical.com/en/pharmacology/erythromycin/)

## Related conditions

- [Helicobacter pylori gastritis](https://durgical.com/en/conditions/helicobacter-pylori-gastritis/)
- [Community-acquired pneumonia](https://durgical.com/en/conditions/community-acquired-pneumonia/)
- [Streptococcal pharyngitis](https://durgical.com/en/conditions/streptococcal-pharyngitis/)

[← Back to the class: Macrolides](https://durgical.com/en/pharmacology/classes/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](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=d836ae7e-fdbf-4dcb-a90d-ede1dcbc3e67) (DailyMed (U.S. National Library of Medicine), 2026); [Clarithromycin: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a692005.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [eEML - Electronic Essential Medicines List](https://list.essentialmeds.org/?query=clarithromycin) (World Health Organization, 2025).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/pharmacology/clarithromycin/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/clarithromycin/