Physostigmine's effect on diminished fetal heart rate variability caused by scopolamine, meperidine and propiomazine

Physostigmine was given to 17 patients in labor, previously given scopolamine alone or meperidine and propiomazine in combination, to ascertain its effect on reversing the loss of fetal heart rate variability caused by the administration of these drugs. The results of the study indicated that scopolamine in doses of 0.65 to 1.08 milligrams diminished fetal heart rate variability in all 7 patients and physostigmine reversed this loss of fetal heart rate variability in all 7 patients within 4 to 17 minutes after injection of the first dose of physostigmine. Similar results were noted in 10 patients with the combination of meperidine, 50 mg, and propiomazine, 20 mg. It seems tenable from this study that physostigmine does cross the placental barrier and enters the fetal circulation and that this usually occurs within 3 to 17 minutes with an average of approximately 9 minutes. In the healthy fetus the loss of fetal heart rate variability caused by scopolamine, meperidine or propiomazine can be reversed by the use of physostigmine and this reversal seems abrupt and clinically measurable on the fetal monitor print out.