Progestagenic effects in general are recognized to be strongly porphyrogenic. No published reports of attacks of acute porphyria connected with exposure to medroxyprogesterone. The substance is listed as inducer of CYP3A4, but there is no clinical evidence supporting significant potency.

Medroxyprogesterone acetate is a synthetic progestin, a derivative of 17 α-hydroxyprogesterone that differs structurally by the addition of a 6 α-methyl group and a 17 α-acetate group.

Medroxyprogesterone is indicated for the treatment of certain hormone dependant neoplasms, such as endometrial carcinoma, renal cell carcinoma, or carcinoma of breast in post menopausal women. It is also used for the treatment of menorrhagia, secondary amenorrhoea, endometriosis or as a contraceptive. It is given orally or, for prolonged action, as an aqueous suspension by intramuscular or subcutaneous injection.

Medroxyprogesterone acetate is metabolised in the liver. It is oxidatively metabolized in the liver to hydroxy derivative and excreted in urine and bile after conjugation. Listed as substrate (Rendic, 2002; Zhou, 2007) and weak inducer of CYP 3A4 (Zhou, 2007). Medroxyprogesterone was found to be a moderate inhibitor of CYP2C9 and weak inhibitor of CYP3A4, but is not a mechanism based-inhibitor (Zhang, 2006).

A low dose (10 mg) of medroxyprogesterone was used in combination with the GnRH agonist buserelin for the treatment of premenstrual attacks of porphyria in one AIP woman and one VP woman, the women did not experience any attacks during this treatment (Bargetzi, 1989).