Oral zidovudine during labor to prevent perinatal HIV transmission, Bangkok: tolerance and zidovudine concentration in cord blood

Objectives: To evaluate tolerance for the oral administration of zidovudine (ZDV) during labor and measure the resulting ZDV concentrations in umbilic al cord blood. Design: A cross-sectional study of women in a placebo-controlled trial of s hort-course ZDV (twice a day from 36 weeks' gestation until labor and every 3 h during labor) to prevent perinatal HIV transmission in Bangkok. Methods: Umbilical cord blood was collected. Sixty control specimens and sp ecimens from 372 women (182 in the ZDV group, 190 in the placebo group) wer e tested for ZDV by radioimmunoassay (lower detection limit < 1 ng/ml). Results: All women in the ZDV group took one or more labor dose, 170 (93%) took their fast dose within 3 h of delivery and only five (3%) experienced nausea or vomiting, a proportion similar to the placebo group. The median c oncentration of ZDV in the cord blood in the ZDV group was 252 ng/ml (range , < 1-1133 ng/ml); 31 (17%) specimens were less than 130 ng/ml (0.5 mu M), the concentration thought to be active against HIV in vitro. Median concent rations were 189 ng/ml in specimens from women taking one or two labor dose s, 290 ng/ml in those taking three or four doses, and 293 ng/ml in those ta king more than four doses (P < 0.01). The ZDV concentration was not associa ted with time since the last dose, body weight, or perinatal transmission. Conclusion: Oral intrapartum ZDV was feasible and well tolerated. Most ZDV concentrations in the cord blood after oral dosing during labor were at the rapeutic concentrations but were lower than those reported after continuous intravenous administration. Although concentrations were not associated wi th perinatal transmission, these data do not exclude the possibility that i ntrapartum and neonatal chemoprophylaxis is effective. (C) 2000 Lippincott Williams & Wilkins.