Acute efficacy of a sublingual dose of nifedipine on uterine arterial blood flow: preliminary data in prematurely menopausal women.

OBJECTIVES To determine whether the calcium blocker nifedipine alters Doppler velocimetry and impedance parameters in the uterine artery in prematurely menopausal women. METHODS Uterine artery Doppler examinations were performed transvaginally in seventeen prematurely menopausal women without the use of calcium blocker (T0). Following a 10-mg sublingual dose of nifedipine patients were subsequently rescanned at successive time intervals (T25 = 25, T40 = 40, T60 = 60 min). PI (normalized (NPI) for heart rate) and maximum, minimum and average velocities of the uterine artery were recorded and waveforms were qualitatively assessed using Goswamy and Steptoe's waveform classification. RESULTS Quantitative analysis showed a significant decrease in NPI at T(25) in the right and left uterine arteries (T0: PI = 2.95 and 3.01; T25: PI = 1.52 and 1.52, respectively; P < 0.001) and until the end of the experiment. Minimum and average blood flow velocities increased strongly (P < 0.001) whereas the maximum velocities did not change significantly (P = 0.12). Qualitative analysis revealed more conspicuous results: eight subjects presented 'abnormal' spectra: one was type A (absence of protodiastole), three were type B (absence of telediastole) and four were type O (no diastolic blood flow); all of them recovered type C waveforms (normal spectrum) during the hour following nifedipine administration. CONCLUSIONS Nifedipine induces a reversible decrease in NPI and an increase in blood flow velocities in the uterine artery in prematurely menopausal women. These results suggest that nifedipine is a potent uterine arterial vasodilator.