Nitroglycerin experiences 'rebirth' as an effective tocolytic agent. (Rapid Uterine Relaxation).

Nitroglycerin has been rediscovered as a tocolytic and as a means of rapid uterine relaxation in childbirth, Dr. Mark Rosen said at a meeting on antepartum and intrapartum management sponsored by the University of California, San Francisco.

Nitroglycerin works by releasing nitric oxide (NO). The first modern successful use of NO was noted in 1989 for manual removal of retained placentae. Since then nitroglycerin has become increasingly popular for use during cerclage placement, tocolysis for fetal distress, internal and external versions, entrapped fetus, cesarean section, and uterine inversion.

"We never stopped using nitric oxide donor agents. But nitroglycerin has certainly had a rebirth," said Dr. Rosen, professor, vice chair, and director of obstetrical anesthesia at the University of California, San Francisco.

Nitroglycerin was reborn as an agent to facilitate uterine relaxation necessary for fetal surgery in the 1980s. Although the primary agents used for this were inhaled halo-genated anesthetics, nitroglycerin was extremely effective as a supplement. By the late 1980s, nitroglycerin was in use as a tocolytic and has since grown in popularity.

It took scientists until the 1980s to understand how the NO released by nitroglycerin worked. By then, it was well established that NO is an endothelium-derived relaxing factor.

The NO released by nitroglycerin activates protein kinases, resulting in reduced calcium inside the cell and smooth muscle relaxation. Studies show that both pregnant and ...