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Macrolide antibiotic

Clarithromycin (ENT Indications)

Brand names: Klaricid

Used in: Pneumonia Cellulitis & Skin Infection

Clarithromycin is a macrolide antibiotic used for respiratory and ENT infections, as part of Helicobacter pylori eradication, and as a penicillin alternative in some indications.

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.

US labelling (FDA)

Reference — US labelling, may differ from UK

Adults : clarithromycin tablets 250 mg or 500 mg every 12 hours for 7 to 14 days ( 2.2 ) H. pylori eradication (in combination with lansoprazole/amoxicillin, omeprazole/amoxicillin, or omeprazole): clarithromycin tablets 500 mg every 8 or 12 hours for 10 to 14 days. See full prescribing information (FPI) for additional information. ( 2.3 ) Pediatric Patients : clarithromycin 15 mg/kg/day divided every 12 hours for 10 days ( 2.4 ) Mycobacterial Infections : clarithromycin tablets 500 mg every 12 hours; clarithromycin tablets 7.5 mg/kg up to 500 mg every 12 hours in pediatric patients ( 2.5 ) Reduce dose in moderate renal impairment with concomitant atazanavir or ritonavir-containing regimens …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2025-10-15. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Clinical monograph

How it works

Clarithromycin binds the bacterial 50S ribosomal subunit, inhibiting protein synthesis (bacteriostatic at usual concentrations).

Prescribing in practice

  • It is a strong CYP3A4 inhibitor with many important interactions — notably statins (myopathy risk), some DOACs, and other QT-prolonging drugs.
  • It can prolong the QT interval; use caution with other QT-prolonging agents and in electrolyte disturbance.
  • Reduce the dose in significant renal impairment.

Monitoring

Short courses need no routine monitoring; review interacting drugs (e.g. temporarily withholding certain statins) and consider ECG/electrolytes where QT risk is high.

Counselling the patient

  • Complete the course; gastrointestinal upset and a metallic taste are common.
  • Tell your clinician about all other medicines, as clarithromycin interacts with many.

Evidence & guidelines

Macrolides are recommended where a penicillin is unsuitable and within H. pylori eradication regimens, subject to local guidance and interaction checks.

Reference: PHE ENT Antimicrobial Guidelines; 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).

Related

Curated clinical cross-links plus same-class fallbacks.

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