Macrolide antibiotic

Clarithromycin

Brand names: Klaricid, Klaricid XL

Clarithromycin is a macrolide antibiotic indicated for common respiratory, ENT and skin infections and as part of combination therapy for Helicobacter pylori eradication.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

Clinical monograph

How it works

It inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit and blocking translocation, and is typically bacteriostatic against susceptible organisms.

Prescribing in practice

Clarithromycin can prolong the QT interval and provoke arrhythmias, so concurrent QT-prolonging medicines and high-risk cardiac patients should be avoided.
As a strong CYP3A4 inhibitor it is contraindicated with simvastatin and several other agents owing to the risk of serious toxicity.
It potentiates warfarin and can increase exposure to colchicine and some other co-prescribed drugs.

Monitoring

Monitor clinically for cardiac, hepatic and interaction-related effects rather than by routine bloods in uncomplicated use.

Counselling the patient

Seek advice if you develop palpitations, blackouts or muscle pain while taking it.
Always disclose your other medicines, as many interact with clarithromycin.

Evidence & guidelines

The cardiac and interaction cautions for clarithromycin are reflected in MHRA advice and its SPC.

Reference: NICE CKS; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Drugs

Pathways