Early abortifacient action of RU 486 by continuous intravenous infusion in rat

RU 486 administered through constant intravenous infusion at 20 mg/kg dose on day 8 of pregnancy induced frank vaginal bleeding and resorption of all implantations in 100% rats. This was associated with an almost 4-fold reduction in progesterone secretion rate by the dispersed luteal cells ex-vivo. At 12 mg/kg dose, an incomplete resorption of implantations was observed in all treated animals. Results indicate that slow and continuous intravenous infusion of this antiprogestin was highly effective in terminating pregnancy shortly after implantation in the rat and this could, at least partially, be related to its luteolytic action in this species.