Cardiovascular and tocolytic effects of nicardipine HCl in the pregnant rabbit: comparison with ritodrine HCl.

Abstract

The effects of two dosage schedules of nicardipine, a calcium-entry blocker, were studied in the pregnant rabbit during induced preterm uterine contractions and compared with the effects of ritodrine hydrochloride. Uterine activity was inhibited by all treatment regimens, but the most significant inhibition was achieved by the higher dose of nicardipine, which nearly abolished all uterine activity. However, while maternal tachycardia and hypotension were observed during treatment with each of these medications, the most significant drop in blood pressure occurred with high-dose nicardipine. These findings may indicate that nicardipine is a potent tocolytic agent with side effects similar in degree, but of different etiology, than those seen with ritodrine. Additional studies to clarify the effect of nicardipine tocolysis on the fetus are needed before it can be considered for use in human pregnancy.