Azithromycin vs erythromycin for the management of preterm premature rupture of membranes

Preterm premature rupture of membranes complicates 2–3% of pregnancies. Many institutions have advocated for the use of azithromycin instead of erythromycin. This is secondary to national shortages of erythromycin, ease of administration, better side effect profile, and decreased cost of azithromycin as compared with erythromycin. The objective of the study was to evaluate whether there are differences in the latency from preterm premature rupture of membranes to delivery in patients treated with different dosing regimens of azithromycin vs erythromycin. This is a multicenter, retrospective cohort of women with singleton pregnancies with confirmed rupture of membranes between 230 and 336 weeks from January 2010 to June 2015. Patients were excluded if there was a contraindication to expectant management of preterm premature rupture of membranes. Patients received 1 of 4 antibiotic regimens: (1) azithromycin 1000 mg per os once (azithromycin 1 day group); (2) azithromycin 500 mg per os once, followed by azithromycin 250 mg per os daily for 4 days (azithromycin 5 day group); (3) azithromycin 500 mg intravenously for 2 days, followed by azithromycin 500 mg per os daily for 5 days (azithromycin 7 day group); or (4) erythromycin intravenously for 2 days followed by erythromycin per os for 5 days (erythromycin group). The choice of macrolide was based on institutional policy and/or availability of antibiotics at the time of admission. In addition, all patients received ampicillin intravenously for 2 days followed by amoxicillin per os for 5 days. Primary outcome was latency from diagnosis of rupture of membranes to delivery. Secondary outcomes included clinical and histopathological chorioamnionitis and neonatal outcomes. Four hundred fifty-three patients who met inclusion criteria were identified. Seventy-eight patients received azithromycin for 1 day, 191 patients received azithromycin for 5 days, 52 patients received azithromycin for 7 days, and 132 patients received erythromycin. Women who received the 5 day regimen were younger and less likely to be non-African American, have hypertension, have sexually transmitted infection, or experienced substance abuse. There was no statistical difference in median latency time of azithromycin 1 day (4.9 days, 95% confidence interval, 3.3–6.4), azithromycin 5 days (5.0, 95% confidence interval, 3.9–6.1), or azithromycin 7 days (4.9 days, 95% confidence interval, 2.8–7.0) when compared with erythromycin (5.1 days, 95% con