Cardiovascular and uterine blood flow changes during nicardipine HCl tocolysis in the rabbit

We studied the changes in cardiovascular performance and uterine blood flow during treatment with nicardipine HCl, a recently developed calcium entry blocker. Pregnant rabbits were surgically prepared for monitoring of uterine activity and blood flow measurements on day 24-26 of gestation. On day 29 of gestation, regular uterine activity was induced and then treated by intravenous nicardipine HCl infusion. Measurements were made before induction of labor and before and after tocolysis. Nicardipine HCl treatment was associated with a rise in pulse rate and concomitant fall in mean arterial pressure. While there was a significant (greater than 40%) increase in cardiac output during tocolysis, there was also a fall in uteroplacental blood flow. The significance of these changes and their implications for fetal well-being need further investigation before clinical studies can begin.