MATERNAL AND FETAL CARDIOVASCULAR-RESPONSES TO METHAMPHETAMINE IN THEPREGNANT SHEEP

OBJECTIVES: Our purpose was to evaluate the maternal and fetal cardiov ascular effects of maternally administered methamphetamine and to dete rmine the extent of placental transfer STUDY DESIGN: Seven near-term p regnant sheep were surgically instrumented to measure maternal and fet al blood pressure and heart rate, cardiac output, uterine flow, and um bilical flow. A single dose of methamphetamine 1 mg/kg was administere d as a bolus to study maternal and fetal cardiovascular responses and placental transfer RESULTS: Maternal administration of methamphetamine caused increases in maternal blood pressure, heart rate, cardiac outp ut, and systemic vascular resistance and decreased uterine blood flow. Peak maternal changes occurred within 10 minutes after methamphetamin e administration and were near baseline by 180 minutes. Fetal blood pr essure increased and returned slowly to baseline by 2 hours. After an initial decrease fetal heart rate increased above baseline values over the next 2 hours. Umbilical blood flow also decreased initially and t hen increased slightly. Fetal pH and PO2 tended to decrease. Maternal and fetal methamphetamine levels reached a maximum of 2.9 and 1.9 mug/ ml, respectively. Rapid and significant placental transfer, delayed ex cretion into the amniotic fluid, and slow elimination from the materna l and fetal circulation were demonstrated. CONCLUSION: Methamphetamine readily crosses the ovine placenta, producing significant and long-la sting maternal and fetal cardiovascular effects, which may have long-t erm consequences, especially if administered repetitively.