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Macrolide Antibiotic — Obstetric

Erythromycin (PPROM / GBS in Pregnancy)

Brand names: Erythrocin, Erymax

Erythromycin is a macrolide antibiotic used in obstetrics for preterm prelabour rupture of membranes (PPROM) and as an option in group B streptococcus (GBS) prophylaxis when penicillin is unsuitable.

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.

Clinical monograph

How it works

Inhibits bacterial protein synthesis by binding the 50S ribosomal subunit, giving bacteriostatic activity against many Gram-positive and atypical organisms.

Prescribing in practice

  • Co-amoxiclav should be avoided in PPROM because of the increased risk of neonatal necrotising enterocolitis, so erythromycin is the preferred agent in this setting.
  • Erythromycin prolongs the QT interval and inhibits CYP3A4, so review concurrent QT-prolonging and interacting drugs before prescribing.
  • Gastrointestinal upset is common and may limit tolerability.

Monitoring

Routine laboratory monitoring is not usually required; monitor for gastrointestinal intolerance and review the maternal and neonatal infection picture.

Counselling the patient

  • Nausea, abdominal cramps and diarrhoea are common side effects.
  • Take the course as directed and complete it even if symptoms settle.
  • Report palpitations or fainting, and mention all other medicines being taken.

Evidence & guidelines

NICE guidance on preterm labour recommends erythromycin in PPROM and advises against co-amoxiclav because of the necrotising enterocolitis signal seen in the ORACLE trial.

Reference: NICE NG25 (Preterm Labour and Birth); ORACLE I Trial; RCOG Green-top 44 (PPROM); 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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