Maternal and fetal cardiovascular effects of transdermal glyceryl trinitrate and intravenous ritodrine

Objective: To determine the maternal and fetal cardiovascular effects of tr ansdermal glyceryl trinitrate compared with ritodrine for acute tocolysis. Methods: Sixty women in preterm labor were enrolled in this study that was part of a multicenter study of glyceryl trinitrate. Once randomized, the wo men received transdermal glyceryl trinitrate or intravenous ritodrine for a cute tocolysis, Measurements of maternal pulse, blood pressure (BP), and fe tal heart rate (FHR) were recorded for up to 24 hours and compared over the treatment course. Results: Changes from baseline in mean maternal heart rate, FHR, and matern al BP (mean arterial pressure [MAP]) were compared between the glyceryl tri nitrate and ritodrine groups over the entire treatment course. The mean cha nge from baseline in maternal heart rate was 21.1 beats per minute less (95 % confidence interval [CI] 15.7, 26.5, P <.001), and the mean maternal hear t rate was 21.8 beats per minute lower (95% CI 16.9, 26.7, P <.001) in the glyceryl trinitrate group. The mean change in FHR was 9.2 beats per minute less (95% CI 3.8, 14.6, P =.001) and the mean FHR significantly lower (6.9 beats per minute, 95% CI 1.9, 11.9, P =.008) during glyceryl trinitrate tre atment. Ritodrine had a significantly hypotensive effect on MAP (95% CI -4. 3, 0.0, P =.03). Mean arterial pressure was not significantly different ove r the treatment course. Conclusion: At doses required for acute tocolysis, transdermal glyceryl tri nitrate had minimal effects on maternal pulse, EP, and FHR, and significant ly fewer adverse cardiovascular effects than intravenous ritodrine. Thus, t ransdermal glyceryl trinitrate might be a safer treatment for women in pret erm labor. (Obstet Gynecol 1999;94:572-6. (C) 1999 by The American College of Obstetricians and Gynecologists.).