Macrolide antibiotic Pregnancy: Use only if benefit outweighs risk — some reports of cardiovascular defects. Avoid in first trimester if possible.

Clarithromycin (ENT Indications)

Brand names: Klaricid

Adult dose

Dose: 250–500 mg twice daily for 5–14 days

Route: Oral or IV

Frequency: Twice daily

Max: 500 mg twice daily (1 g/day)

Tonsillitis/pharyngitis (penicillin allergy): 250 mg BD for 5 days. Acute sinusitis (penicillin allergy): 250–500 mg BD for 5 days. Community pneumonia (atypicals): 500 mg BD. H. pylori triple therapy: 500 mg BD + amoxicillin + PPI. IV: 500 mg BD for severe infections.

Paediatric dose

Dose: 7.5 mg/kg

Route: Oral

Frequency: Twice daily

Max: 500 mg/dose

Concentration: 125 mg/ml

1 month–11 years: 7.5 mg/kg BD (max 250 mg BD standard; 500 mg BD severe). 12–17 years: adult dose. Granules or suspension for younger children (125 mg/5 mL).

Dose adjustments

Renal

If eGFR <30: halve dose or double interval. Avoid prolonged high-dose use.

Hepatic

Avoid in severe hepatic disease; caution in moderate impairment.

Paediatric weight-based calculator

Patient weight (kg)

1 month–11 years: 7.5 mg/kg BD (max 250 mg BD standard; 500 mg BD severe). 12–17 years: adult dose. Granules or suspension for younger children (125 mg/5 mL).

Clinical pearls

Alternative to amoxicillin for penicillin-allergic patients with respiratory/ENT infections
Active against Group A Streptococcus, Moraxella, H. influenzae (limited), atypical organisms
Significant CYP3A4 inhibitor — numerous drug interactions
Metallic taste common — take with food to reduce GI side effects
AVOID with simvastatin or lovastatin — statin myopathy risk

Contraindications

QT prolongation or Torsades de Pointes history
Concomitant use of QT-prolonging drugs
Hypersensitivity to macrolides

Side effects

GI upset (nausea, abdominal pain, diarrhoea)
Metallic taste
QT prolongation
Elevated liver enzymes
Antibiotic-associated colitis
Hearing disturbance (high doses)

Interactions

Statins (simvastatin, atorvastatin) — increased myopathy risk (avoid combination or reduce statin dose)
Warfarin — significantly increases INR
Ciclosporin, tacrolimus — increased levels
Colchicine — increased toxicity (avoid if renal/hepatic impairment)
Carbamazepine — increased carbamazepine levels

Monitoring

LFTs (prolonged use)
Drug interactions
ECG (if QT risk)

Reference: BNFc; BNF; BNFc; PHE ENT Antimicrobial Guidelines. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Drugs

Pathways