To test the hypothesis that chronic exposure to cocaine would alter drug el
imination in pregnant and fetal sheep compared to a single exposure, we adm
inistered intravenous cocaine HCl to 8 pregnant sheep daily as a bolus, fol
lowed by a 2-h infusion beginning at gestational age 75 days. Eight additio
nal animals received an equivalent volume of saline. Three days after mater
nal and fetal catheter placement on day 125, ewes in both groups received c
ocaine HCl, 2 mg/kg, as a bolus. Maternal and fetal plasma samples were ser
ially obtained and analyzed for cocaine and benzoylecognine. Cocaine half-l
ife in the ewes and fetuses exposed to cocaine was no different from that i
n animals exposed to saline. We conclude that cocaine is rapidly metabolize
d in pregnant sheep and that chronic administration does not alter drug cle
arance.