THE MATERNAL-FETAL TRANSFER OF LAMIVUDINE IN THE EX-VIVO HUMAN PLACENTA

OBJECTIVE: Our purpose was to measure the transfer of lamivudine ([-]- 2'-deoxy-3'-thiacytidine] across the human placenta both alone and in the presence of zidovudine. STUDY DESIGN: Nine placentas from term, el ective cesarean deliveries were analyzed with use of the ex vivo singl e cotyledon perfusion system. Antipyrine was used as the reference com pound to measure the clearance index values of lamivudine alone and in combination with zidovudine. Lamivudine concentrations in the perfusa tes and tissues were quantified by high-pressure liquid chromatography . RESULTS: The clearance index of lamivudine at a maternal concentrati on of 1.39 mu g/ml was 0.23 +/- 0.14. At a peak concentration of 14.68 mu g/ml the clearance index was 0.14 +/- 0.06. These index values did not significantly change in the presence of 1 or 10 mu g/ml of zidovu dine. In a closed recirculating system the fetal lamivudine concentrat ion increased as more lamivudine was added to the maternal perfusate. The addition of zidovudine did not influence this transfer. CONCLUSION : Lamivudine appears to cross the placenta by simple diffusion and its transfer does not appear to be altered by zidovudine.