Intravenous administration of cocaine stimulates gravid baboon myometrium in the last third of gestation

Abstract

OBJECTIVE: The hypothesis for this investigation was that intravenous cocaine results in a dose-dependent increase in myometrial activity of the unanesthetized, chronically instrumented gravid nonhuman primate. STUDY DESIGN: Seven chronically instrumented gravid baboons were individually caged in an environment of 14 hours of light and 10 hours of darkness. Maternal femoral artery and vein catheters and three pairs of myometrial electromyographic wires were surgically placed at 90 to 121 days' gestation (term 180 days). At least 5 days after surgery, bolus intravenous cocaine hydrochloride doses of 0.05, 0.1, 0.3, 0.5, and 1.0 mg/kg maternal body weight were administered according to various schedules. Myometrial activity was analyzed by quantifying the myometrial electromyographic envelope data as the power spectral density window of contraction activity and as the total area under the rectified electromyographic voltage signal (i.e., total electromyographic activity) before and during the experimental period. RESULTS: Myometrial contraction activity increased after the 0.3 mg/kg dose (p < 0.01), the 0.5 mg/kg dose (p < 0.005), and the 1.0 mg/kg dose (p = 0.07) compared with baseline. The total myometrial electromyographic activity also increased as the cocaine dose increased. CONCLUSION: Intravenous cocaine results in increased myometrial contractions in the gravid baboon during the latter third of pregnancy. (AM J OBSTET GYNECOL 1994;170:1416-20.)