Adjunctive azithromycin cuts postcesarean infection

Adding a single intravenous dose of azithromycin to standard antibiotic prophylaxis further reduces maternal infections without increasing neonatal adverse outcomes after nonelective cesarean delivery, according to a report published in the New England Journal of Medicine.

The adjunctive azithromycin also significantly decreased rates of postpartum fever and of readmission or unscheduled office visits, wrote Alan T.N. Tita, MD, PhD, of the University of Alabama at Birmingham, and his colleagues.

Recent studies have suggested that extended-spectrum prophylaxis using azithromycin, when added to standard cephalosporin prophylaxis, would further reduce the incidence of post-cesarean infection, chiefly because of azithromycin’s coverage of ureaplasma species that are frequently associated with these infections. The C/SOAP (Cesarean Section Optimal Antibiotic Prophylaxis) trial tested this hypothesis in 2,013 women who underwent nonelective cesarean delivery of singleton neonates at 14 U.S. hospitals during a 3.5-year period.

All the women received standard antibiotic prophylaxis (usually with cefazolin) and were randomly assigned to receive either a 500-mg dose of azithromycin (1,019 participants) or a matching placebo (994 participants) before surgical incision.

The primary outcome measure – a composite of endometritis; wound infection; or other infections such as abdominopelvic abscess, maternal sepsis, pelvic septic thrombophlebitis, pyelonephritis, pneumonia, or meningitis occurring up to 6 weeks after surgery – developed in half as many women in the azithromycin group (6.1%) as in the placebo group (12.0%). The relative risk (RR) was 0.51 (P less than .001).

Azithromycin, in particular, was associated with significantly lower rates of endometritis (3.8% vs. 6.1%; RR, 0.62; P = .02) and wound infection (2.4% vs. 6.6%; RR, 0.35; P less than .001). This benefit extended across all subgroups of patients regardless of study site, maternal obesity status, the presence or absence of membrane rupture at randomization, preterm or term delivery, or maternal diabetes status.

The number of patients who would need to be treated to prevent one study outcome was 17 for the primary outcome, 43 for endometritis, and 24 for wound infections, the researchers reported (N Engl J Med. 2016 Sep 29;375:1231-41).

Serious maternal adverse events also were less common with azithromycin (1.5%) than with placebo (2.9%). Neonatal outcomes did not differ between the study groups. The rate of combined neonatal death or complications was 14.3% with azithromycin and 13.6% with placebo, a nonsignificant difference.

The study was supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development. Pfizer donated the azithromycin used in the trial. Dr. Tita reported having no relevant financial disclosures; his colleagues reported ties to numerous industry sources.