Macrolides · Anti-infectives
Clarithromycin
Biaxin®(brand names vary by market)
An effective antibiotic and a potent CYP3A4 inhibitor in the same tablet.
Also: oral liquid, modified release
Mechanism
50S ribosomal binding, as with the other macrolides, plus strong inhibition of CYP3A4, which is where most of its clinical trouble comes from.
Indications
- Helicobacter pylori eradication regimens
- Community-acquired pneumonia
- Skin and soft tissue infection
- Mycobacterium avium complex
Formulations
Dosing concepts
H. pylori
Used as part of a multi-drug regimen and avoided where local macrolide resistance is high or the patient has had a recent macrolide course.
Interaction management
The usual approach with a statin is to hold it for the duration of the course rather than to accept the interaction.
Concepts, not prescribing instructions. Practice numbers live in current references and local protocols.
Pharmacokinetics
- Bioavailability
- ~50%
- Half-life
- 3 to 7 h
- Elimination
- hepatic: CYP3A4 substrate and potent inhibitor; an active metabolite adds to the effect
- Protein binding
- ~70%
Adverse effects
- Metallic tastecommonCharacteristic and distinctive.
- Gastrointestinal upsetcommon
- QT prolongationserious
- Hepatotoxicityserious
- Interaction-mediated harmseriousRhabdomyolysis with statins, bleeding with warfarin, hypotension with calcium channel blockers, colchicine toxicity.
Contraindications & precautions
Contraindications
- Concurrent simvastatin or lovastatin
- Concurrent colchicine in renal or hepatic impairment
- Known QT prolongation with other risk factors
- Prior macrolide cholestatic jaundice
Precautions
- Concurrent CYP3A4-dependent drugs
- Renal impairment
- Cardiac disease
Interactions
- Warfarin + Clarithromycin / erythromycincautionINR climbs within days of starting the antibiotic.
- Simvastatin / atorvastatin + Clarithromycin, itraconazole, ritonavir (strong CYP3A4 inhibitors)avoidMyopathy up to rhabdomyolysis: muscle pain, dark urine, AKI.
- Broad-spectrum antibiotics (any) + WarfarinmonitorModest INR rise, additive with any CYP effect of the specific agent.
- Amlodipine / felodipine + Strong CYP3A4 inhibitors; grapefruit (felodipine)monitorMore vasodilation: flushing, edema, hypotension.
Monitoring
The rest of the medication list, before the first dose
This is a drug whose main risk is what else the patient takes
INR in warfarin patients
One of the sharpest interactions in practice
Muscle symptoms if a statin was continued
Rhabdomyolysis
Counselling points
- Tell us every other medicine you take, including over-the-counter ones, before starting this.
- Your cholesterol tablet may be paused for a few days; that is deliberate.
- A metallic taste is common and harmless.
- Report muscle pain or weakness.
Clinical pearls
- The clarithromycin plus simvastatin combination has caused fatal rhabdomyolysis and is a hard contraindication rather than a caution. Rosuvastatin and pravastatin are the statins that survive the interaction.
- Clarithromycin plus colchicine in a patient with renal impairment is another documented fatal combination, and colchicine is easy to overlook because the patient only takes it for flares.
References & review
- Clarithromycin product monograph (consult the current version for your market) (monograph)
- Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed. (reference-work)
Last reviewed 2026-08-16 · jurisdiction: global · drug information changes; verify against current references before practice use.