Myometrial activity in first trimester human pregnancy after Epostane therapy. Effect of intravenous oxytocin

The effect on myometrial activity of Epostane, a competitive inhibitor of the 3 beta-hydroxy steroid dehydrogenase enzyme system (3 beta-HSD) has been studied in 20 women awaiting termination of pregnancy. The women were randomly allocated by a double-blind procedure into two groups. In the Epostane-treated group there were significant falls in serum progesterone and oestradiol concentrations after 3 days of treatment. The placebo-treated group showed a small but significant decline in serum progesterone concentration. Insertion of an intrauterine balloon catheter for pressure measurements produced significantly greater uterine activity in the Epostane-treated group. The oxytocin response was variable and there was no significant difference between the two groups. A small rise in the peripheral plasma concentration of a prostaglandin F2 alpha metabolite (PGFM) was observed in the placebo group following oxytocin injection. There was a significant inverse correlation between post treatment progesterone values and uterine activity. Epostane appears to sensitize the myometrium to endogenous oxytocics and this probably results from progesterone 'withdrawal'. This effect may prove useful in potentiating the action of exogenous myometrial stimulants, such as prostaglandins, and may have a role in the termination of early pregnancy.