Serum medroxyprogesterone acetate (MPA) concentrations and ovarian function following intramuscular injection of depo-MPA.

ABSTRACT

PIP: Serum medroxyprogesterone acetate (MPA) concentrations were measured by a newly developed, highly sensitive, radioimmunoassay technique, and ovarian function was evaluated in 3 women after a single im injection of MPA (150 mg). Initial MPA concentrations ranged from 1.5 to 3 ng/ml for the 1st few days, and then gradually declined to a relatively constant level of about 1 ng/ml for 2-3 months. During the 6th month, MPA concentrations had declined to about .2 ng/ml, and became undetectable between 7!-9 months. Serum estradiol levels remained at early or midfollicurlar phase values for 4-6 months following injection, and then increased to preovulatory values (.25-.5 ng/ml). However, ovulation did not occur as determined by serum progesterone concentrations. Prolonged suppression of ovarian function by depo-MPA is due to the slow release of MPA; from the injection site.