Macrolide antibiotic

Clarithromycin

Brand names: Klaricid, Klaricid XL

Adult dose

Dose: PO 250–500mg BD; XL 500mg OD. IV 500mg BD

Route: PO/IV

Frequency: BD

Paediatric dose

Dose: 7.5 mg/kg

Route: PO

Frequency: BD

Max: 500mg/dose

Concentration: 25 mg/ml

Standard 7.5 mg/kg BD; severe infections up to 15 mg/kg/day

Dose adjustments

Renal

CrCl <30: halve dose

Paediatric weight-based calculator

Patient weight (kg)

Standard 7.5 mg/kg BD; severe infections up to 15 mg/kg/day

Clinical pearls

First-line CAP penicillin-allergic; H. pylori eradication component
ECG if cardiac risk; many CYP3A4 interactions

Contraindications

History of QT prolongation
With ergot alkaloids
Concurrent astemizole/cisapride/domperidone (potent CYP3A4 inhibition)
Severe hepatic impairment + renal impairment

Side effects

GI upset
Taste disturbance
QT prolongation
Hepatotoxicity
C. difficile
Worsening myasthenia gravis

Interactions

Major: simvastatin/atorvastatin (myopathy — avoid)
Warfarin (raised INR)
Colchicine (toxicity)
Digoxin
Tacrolimus/ciclosporin
Direct oral anticoagulants

Monitoring

LFTs if prolonged
ECG if QT risk

Reference: BNFc; BNF; NICE CKS; https://bnf.nice.org.uk/drugs/clarithromycin/. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

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