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Macrolide Antibiotic — STI Treatment Pregnancy: Preferred macrolide in pregnancy for chlamydia — superior to doxycycline (contraindicated) and erythromycin (GI tolerability)

Azithromycin (Chlamydia / STI in Pregnancy)

Brand names: Zithromax

Adult dose

Dose: 1 g oral single dose (chlamydia); 2 g oral single dose (gonorrhoea — with ceftriaxone)
Route: Oral
Frequency: Single dose
Max: 2 g single dose
BASHH guidelines: Chlamydia trachomatis — azithromycin 1 g single dose (preferred in pregnancy over doxycycline). Gonorrhoea: ceftriaxone 1 g IM + azithromycin 2 g oral (dual therapy). Always test of cure 2 weeks after treatment in pregnancy

Paediatric dose

Dose: Not applicable in this STI context N/A/kg
Route: Oral
Frequency: N/A
Max: N/A
Maternal medication for STI treatment in pregnancy

Dose adjustments

Renal

No dose adjustment required

Hepatic

Avoid in severe hepatic impairment — hepatically metabolised

Paediatric weight-based calculator

Maternal medication for STI treatment in pregnancy

Clinical pearls

  • Chlamydia in pregnancy: azithromycin 1 g single dose is preferred over doxycycline (contraindicated in pregnancy) — improved bone and tooth safety; BASHH recommends test of cure at 5-6 weeks post-treatment
  • Gonorrhoea in pregnancy: dual therapy mandatory — ceftriaxone 1 g IM + azithromycin 2 g oral; single-agent treatment inadequate due to resistance; BASHH 2019
  • QT prolongation: MHRA 2013 warning — azithromycin prolongs QT; single 1-2 g doses carry lower cumulative risk than courses; obtain ECG if baseline QT concern
  • Neonatal chlamydia: untreated maternal chlamydia causes neonatal conjunctivitis and pneumonia — treatment of the mother is the most effective prevention
  • Partner notification: essential for all STI diagnoses — contact public health / GUM clinic for tracing

Contraindications

  • Hypersensitivity to macrolides
  • QT prolongation or drugs that prolong QT

Side effects

  • GI upset (nausea, diarrhoea)
  • QT prolongation
  • Transient liver enzyme elevation
  • Ototoxicity (high doses — rare)

Interactions

  • QT-prolonging drugs (additive risk)
  • Warfarin (increased INR — monitor)
  • Antacids (reduce peak concentration — separate by 1 hour)

Monitoring

  • Test of cure (5-6 weeks post-treatment)
  • QTc if risk factors present

Reference: BNFc; BNF 90; BASHH Chlamydia Guidelines 2018; BASHH Gonorrhoea Guidelines 2019; MHRA QT alert 2013. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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