Epostane acts as an antiprogestogen and terminates pregnancy by inhibiting 3β-hydroxysteroid dehydrogenase and preventing the biosynthesis of progesterone and pregnenolone. [4]

METHODS: Using one fish oocyte, the ovary was cut into small pieces and incubated with Epostane (1 μg/mL), and the incidence of germinal vesicle breakdown (GVBD) was examined microscopically
RESULTS Epostane induced a significant decrease in the frequency of GVBD in oocytes, but Epostane failed to eliminate the maturation effect of 17α,20 β-diOHprog, the most potent maturation-inducing steroid in this species.

METHODS: A single-dose, randomized, double-blind study was conducted in which each woman awaiting termination of pregnancy was administered either 50 mg Epostane or 100 mg Epostane orally, and the effects of in vivo serum luteinizing hormone (P), estradiol (E2), and cortisol were determined.
RESULTS Both serum P concentrations decreased significantly, and a similar decrease in serum E2 was observed, with subsequent normalization of E2. [1]
METHODS: Seventy-eight healthy women were recruited to the study who were less than 49 days from their last menstrual period and requested termination of pregnancy, 200 mg Epostane four times daily for a total of 7 days.
RESULTS The complete abortion rate in the Epostane group was 73%. [2]