Transfer of cocaine and benzoylecgonine across the perfused human placental cotyledon

OBJECTIVE: Our aim was to measure the transfer of cocaine and its major metabolite benzoylecgonine across the human term placenta. STUDY DESIGN: By means of in vitro perfusion of the human term placental cotyledon the transfer of these compounds was measured. RESULTS: The steady-state maternal-to-fetal transfer of cocaine (0.18 ± 0.05 μg/ml/min) was significantly greater than benzoylecgonine transfer (0.02 ± 0.01 μg/ml/min) (p < 0.05). When the perfused tissue was analyzed 32% ± 7% of the maternal cocaine dose was retained by the placental tissue, whereas only 12% ± 12% of the maternal benzoylecgonine dose was retained by the placental compartment. CONCLUSIONS: These results suggest (1) the placenta may serve as a depot for large amounts of cocaine, thus offering some degree of fetal protection after bolus administration; (2) fetal exposure may be prolonged by placental retention and subsequent release of cocaine and benzoylecgonine; and (3) benzoylecgonine does not cross the placenta as readily as does cocaine. Variability in placental handling of cocaine and benzoylecgonine may therefore determine fetal exposure to these agents. (AM J OBSTET GYNECOL 1994;170:1404-10.)