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Plasma medroxyprogesterone acetate levels following intramuscular or oral administration in patients with endometrial adenocarcinoma.


The concentration of medroxyprogesterone acetate (MPA) in plasma samples taken 24 h after intramuscular or oral administration of 100 mg daily doses of the drug to patients with endometrial adenocarcinoma was measured by radioimmunoassay. In general, a plasma level of about 4 ng/ml was found 24 h after the dose, independent of the route of drug administration. However, in three of the patients to whom intramuscular MPA was given, considerably higher values were found. A maximal plasma level was achieved three hours after ingestion of 100 mg MPA. This was followed by a rapid decline to 20-25% of the peak value after about 12 h. A rather small day-to-day intraindividual variation was found in daily blood samples taken just before administration of the next dose. However, considerable differences were found between individuals and it is concluded that this variation in plasma levels may be reflected in the clinical efficacy of the treatment. Thus further studies in which plasma values and clinical effectiveness are correlated seem to be indicated.


Past studies have shown that patients with recurrent or advanced endometrial carcinoma respond favorably to treatment with progestin. Theories relate the success of the treatment to the concentration of progestin in the blood supplied to cancerous tissues. A study was undertaken to measure the plasma level of the steroid in patients with endometrial adenocarcinoma. Medroxyprogesterone Acetate (MPA) was administered to two groups of patients. One group received a single 100mg dose of MPA intramuscularly every day. The other group was subdivided and individuals received from 100 to 300mg of MPA orally everyday for a month. Plasma levels of MPA were measured daily twenty-four hours after the last dose. Radioimmunoassay techniques were used to measure MPA levels. Plasma levels of patients receiving 100 mg either orally or intramuscularly were the same. Patients who received the 200 mg and 300 mg dosage of MPA orally exhibited higher mean plasma values. Examination of cancerous tissues removed by surgery near the time of plasma MPA evaluation showed marked effects of the therapy. Two of the four patients who had the surgery had received the higher 200mg and 300mg dosage. Based on the results of this investigation, further studies on the effectiveness of treatment for recurrent or advanced endometrial adenocarcinoma should include a phase to monitor MPA plasma levels.

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