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

The aim was to evaluate tolerance for the oral administration of zidovudine (ZDV) during labor and measure the resulting ZDV concentrations in umbilical cord blood. A cross-sectional study was conducted on women in a placebo-controlled trial of short-course ZDV (twice a day from 36 weeks gestation until labor and every 3 hours during labor) to prevent perinatal HIV transmission in Bangkok. Umbilical cord blood was collected. 60 control specimens and specimens from 372 women (182 in the ZDV group 190 in the placebo group) were tested for ZDV by radioimmunoassay (lower detection limit <1 ng/ml). All women in the ZDV group took one or more labor dose 170 (93%) took their last dose within 3 hours of delivery and only 5 (3%) experienced nausea or vomiting a proportion similar to the placebo group. The median concentration of ZDV in the cord blood in the ZDV group was 252 ng/ml (range <1-1133 ng/ml); 31 (17%) specimens were <130 ng/ml (0.5 mcM) the concentration thought to be active against HIV in vitro. Median concentrations were 189 ng/ml in specimens from women taking 1 or 2 labor doses 290 ng/ml in those taking 3 or 4 doses and 293 ng/ml in those taking more than 4 doses (P < 0.01). The ZDV concentration was not associated with time since the last dose body weight or perinatal transmission. Oral intrapartum ZDV was feasible and well tolerated. Most ZDV concentrations in the cord blood after oral dosing during labor were at therapeutic concentrations but were lower than those reported after continuous intravenous administration. Although concentrations were not associated with perinatal transmission these data do not exclude the possibility that intrapartum and neonatal chemoprophylaxis is effective. (authors)