Prenatal cocaine exposure to the fetus: a sheep model for cardiovascular evaluation

Transplacental passage of cocaine in response to maternal administration of intravenous (IV) cocaine in doses of 1.0 and 2.0 mg/kg was studied in 6 pregnant ewes and fetuses and correlated with maximum changes in maternal and fetal blood pressures (BP), heart rates (HR) and fetal arterial blood gas values. Certain animals were given larger doses (3.0 and 5.0 mg/kg) of cocaine to examine cocaine-related cardiopulmonary and neurologic sequelae. Cocaine was extracted on C-18 sorbent columns and analyzed by gas chromatography. At 1.0 and 2.0 mg/kg, cocaine produced dose-dependent increases in maternal HR and BP which were maximum by 1 minute. The fetal response was characterized by maximum increases in BP and decreases in PO2 by 3 minutes and increases in HR by 15 minutes. Cocaine rapidly appeared in the fetal circulation, was approximately 15% of maternal concentrations by 5 minutes, and was undetectable in both circulations by 60 minutes. At cocaine doses of 3.0 and 5.0 mg/kg significant maternal cardiopulmonary and neurologic complications were encountered including bradyarrhythmias, respiratory distress, seizure and death. These data indicate that cocaine exerts direct drug actions upon maternal cardiovascular and neurologic function. In addition, cocaine affects fetal cardiovascular function directly via transplacental passage and indirectly by fetal hypoxemia from cocaine-induced uterine artery vasoconstriction. (NIDA 04415)