A pilot study on the assessment of a progesterone/estradiol sustained release as once-a-month-injectable contraceptive.

A pilot study to assess the use of natural hormones in macrocrystalline sustained release system was undertaken in normal menstruating women. Progesterone at a dose of 100 mg in combination with 5 mg estradiol-17 beta aqueous macrocrystalline suspension (3ml) of defined particle size range (100-250 microns) were administered to five female volunteers of reproductive age, on day 5 of their normal menstrual cycles and then every 28 days consecutively for the next two months. Peripheral venous blood samples were obtained from the women three times a week for 60 days after the third injection for the measurement of serum progesterone, estradiol-17 beta, LH and FSH. The menstrual bleeding patterns were closely monitored during the study period. The results obtained indicate that the exogenous hormone administration produces blood levels similar to those observed during the luteal phase of the menstrual cycle. Follicular maturation as assessed by endogenous estradiol rise, above 150 pg/ml, occurred 29.7 days s.d. 6.4 after the injection. Ovulation as measured by progesterone levels above 5 ng/ml was documented 34.4 days s.d. 4.3 after the third injection. The bleeding patterns were regular though initially shorter but these increased progressively towards normal pattern during course of the study. The data suggest that progesterone/estradiol-17 beta combination administered as an aqueous macrocrystalline suspension is capable of producing sustained ovulation inhibition and could be applied in the design of new once-a-month injectable contraceptives.