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First-Generation Macrolide — Penicillin Allergy Alternative / Gastroparesis Prokinetic Pregnancy: Safe (except estolate formulation) — erythromycin widely used in pregnancy; azithromycin preferred for macrolide atypical cover

Erythromycin

Brand names: Erythrocin, Erythroped, Tiloryth

Adult dose

Dose: Infection: 250–500 mg every 6 hours orally; IV: 6.25–12.5 mg/kg every 6 hours; Gastroparesis (prokinetic): 250 mg 3–4 times daily before meals
Route: Oral or IV
Frequency: 4 times daily
Max: 4 g/day
Oldest macrolide — fewer interactions than clarithromycin. Used as penicillin allergy alternative for respiratory infections, skin infections, STIs (chlamydia), pertussis. As prokinetic: stimulates motilin receptors in GI tract — accelerates gastric emptying. IV formulation causes significant phlebitis — central line preferred for IV use.

Paediatric dose

Dose: 12.5 mg/kg mg/kg
Route: Oral
Frequency: 4 times daily
Max: 2 g/day
BNFc: suspension available (125, 250, 500 mg/5 mL); used for pertussis, chlamydia conjunctivitis in neonates, penicillin allergy

Dose adjustments

Renal

No dose adjustment required

Hepatic

Use with caution — hepatically metabolised; cholestatic jaundice risk (erythromycin estolate formulation — avoid in hepatic impairment)

Paediatric weight-based calculator

BNFc: suspension available (125, 250, 500 mg/5 mL); used for pertussis, chlamydia conjunctivitis in neonates, penicillin allergy

Clinical pearls

  • Prokinetic use: well-established for gastroparesis (especially diabetic) and ICU gastric emptying — mechanism distinct from metoclopramide (motilin agonist not dopamine antagonist); tachyphylaxis develops within days — often used for short periods
  • GI side effects are the major limitation — nausea/vomiting in up to 50% of patients; azithromycin or clarithromycin preferred when available
  • Pertussis: erythromycin (or azithromycin) for 7–14 days — reduces infectivity even if does not alter course once cough established; give to household contacts
  • Phlebitis with IV: dilute to <1 mg/mL and use large vein or central line

Contraindications

  • Concurrent cisapride, pimozide, or ergotamine
  • QT prolongation
  • Erythromycin estolate in hepatic impairment

Side effects

  • GI upset (nausea, vomiting, diarrhoea — very common)
  • QTc prolongation
  • Cholestatic jaundice (especially estolate form)
  • Phlebitis (IV)
  • Hearing loss (high doses)
  • Dysgeusia

Interactions

  • Warfarin — enhanced anticoagulant effect
  • Statins (simvastatin) — increased statin levels
  • Digoxin — increased levels
  • Carbamazepine — increased levels
  • Theophylline — reduced clearance (toxicity)
  • Colchicine — toxicity (less potent CYP3A4 inhibitor than clarithromycin)

Monitoring

  • ECG (QTc)
  • LFTs (cholestatic jaundice)
  • Hearing (high-dose/prolonged courses)
  • Theophylline levels if co-prescribed

Reference: BNFc; BNF 90; PHE Antibiotic Guidelines; NICE Pertussis Guidance; MHRA QT Prolongation Guidance. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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