title: Radioimmunoassay of serum medroxyprogesterone acetate (Provera) in women following oral and intravaginal administration.
abstract: A radioimmunoassay (RIA) method for measuring medroxyprogesterone acetate (MPA, Provera) in serum has been developed utilizing benzene:iso-octane extraction, 3H-MPA to assess procedural losses, goat anti-MPA-3-(0-carboxymethyl) oxime-bovine serum albumin serum and dextran-coated charcoal separation. Control serum blanks were undetectable, 200 pg/ml of MPA was measurable with a high reliability, and intra- and interassay coefficients of variation were 6 and 13 percent, respectively. MPA added to control serum was quantitatively recovered. Serum MPA levels measured in 2 women after ingestion of 10 mg MPA rose to 3.4 to 4.4 ng/ml within 1 to 4 hours after oral intake and fell rapidly thereafter to 0.3 to 0.6 ng/ml within 24 hours. Insertion of Silastic intra-vaginal rings (IVRs), containing 100 or 200 mg of MPA, into 4 women for periods of 3 weeks resulted in a rapid rise of serum MPA after insertion, rather stable MPA levels of 0.9 to 1.6 ng/ml while the IVRs were in place, and a rapid decline of serum MPA following IVR removal. Serum estradiol-17beta and progesterone concentrations, measured about 3 times a week in these patients, indicated that ovulation was consistently inhibited. The serum MPA levels observed in this study were approximately 5 times lower than those reported by other investigators using a double-antibody RIA of MPA in unextracted serum.
mesh_terms: D000284:Administration, Oral; D000328:Adult; D004958:Estradiol / Q000097:blood; D005260:Female; D006801:Humans; D008525:Medroxyprogesterone / Q000008:administration & dosage / Q000097:blood* / Q000276:immunology; D011374:Progesterone / Q000097:blood; D011863:Radioimmunoassay; D013997:Time Factors; D014621:Vagina
chemical_list: D011374:Progesterone; D004958:Estradiol; D008525:Medroxyprogesterone