Abstract
17α-hydroxyprogesterone caproate (Proluton Depot®, Schering AG, Berlin) was given after ovulation in a dose of 500 mg intramuscularly to four women with normal menstrual cycles. The plasma levels of progesterone and oestradiol were measured and compared to the levels found during previous control cycles of the same women. In the four normal women a small reduction of the plasma levels of progesterone and oestradiol was found after the injection of 500 mg of 17α-hydroxyprogesterone caproate. However, the number of days with progesterone concentrations above the mean level of the follicular phase was not changed. The menstrual bleeding was delayed and appeared to be a withdrawal bleeding from 17α-hydroxyprogesterone caproate rather than from progester one.