What is the recommended dose of azithromycin (AZM) for laboring women undergoing cesarean section?

Azithromycin Dosage for Cesarean Section in Laboring Women

For women in labor undergoing cesarean section, a single dose of 500 mg intravenous azithromycin should be administered 30-60 minutes before skin incision, in addition to standard antibiotic prophylaxis (typically cefazolin). 1

Standard Prophylactic Regimen

• The primary prophylactic regimen for cesarean section consists of cefazolin plus azithromycin for women in labor or with ruptured membranes 1
• Cefazolin dosing should be weight-based:
  • 2g IV if BMI <30 kg/m² 1, 2
  • 3g IV if BMI ≥30 kg/m² 1, 2
• Azithromycin should be administered as a single 500 mg IV dose 1, 3
• Both antibiotics should be given 30-60 minutes before skin incision, not after cord clamping 1

Evidence Supporting Azithromycin Addition

• Adding azithromycin to standard cefazolin prophylaxis significantly reduces postoperative infections in women undergoing cesarean delivery during labor or after membrane rupture 3
• Clinical trials demonstrate significant reductions in:
  • Surgical site infections (15% vs 3%, p=0.03) 4
  • Endometritis (8% vs 2%, p=0.048) 4
  • Post-operative febrile morbidity (17% vs 3%, p=0.001) 4
  • Overall composite infection rates (6.1% vs 12.0%, p<0.001) 3

Timing Considerations

• Antibiotics should be administered 30-60 minutes before skin incision 1
• This timing is superior to the older practice of administering after cord clamping 2
• No additional doses are needed if the procedure lasts less than 4 hours 1

Special Considerations

• For patients with penicillin/cephalosporin allergy, clindamycin 900 mg IV is recommended instead of cefazolin 1
• Azithromycin prophylaxis has also been shown to reduce:
  • Hospital stay by approximately 2 days 4
  • Need for additional postoperative antibiotics 4
  • Long-term complications such as cesarean scar defects (32.7% vs 46.3%, p=0.043) 5

Recent Evidence

• A 2023 study showed that adjunctive azithromycin prophylaxis is beneficial even for prelabor cesarean deliveries, with lower odds of composite infection (3.3% vs 4.8%, adjusted OR 0.60) 6
• The combination of cefazolin plus azithromycin has been shown to reduce endometritis rates to very low levels without increasing neonatal sepsis evaluations 2

Clinical Pitfalls to Avoid

• Do not delay administration until after cord clamping, as pre-incision administration is significantly more effective 1, 2
• Do not omit azithromycin for laboring women, as the combination therapy is superior to cefazolin alone 1, 3
• Ensure proper dosing of cefazolin based on patient's BMI to optimize prophylaxis 1, 2