The Plasma Concentration of Medroxyprogesterone Acetate and Ovarian Function During Treatment with Medroxyprogesterone Acetate in 5 and 10 mg Doses

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Abstract
Peripheral plasma levels of medroxyprogesterone acetate (MPA) [contraceptive] were determined by radioimmunoassay in 5 women after oral administration of 5 and 10 mg MPA daily. Peak levels of MPA in plasma were recorded within 1-3 h of taking the tablet, which indicates a rapid absorption from the gastro-intestinal tract. The levels of MPA 12 h after taking of the 5 mg tablet remained constant throughout the 8 wk of study. Peripheral plasma levels of estradiol and progesterone were determined throughout treatment. The estradiol levels indicated development of follicles in 7 of 10 treatment months in the 5 mg group, and in 3 of the subjects treated with 10 mg MPA. The progesterone levels in those women treated with 5 mg MPA showed normal luteal concentration values in 2 of 10 treatment months. No woman treated with 10 mg MPA had an increase in progesterone during the 21-day period of treatment. MPA (10 mg) daily will inhibit ovulation but 5 mg is not sufficient to inhibit ovulation in all women.