9.2 Drug Interactions Overview
Medroxyprogesterone acetate is metabolized in-vitro primarily by hydroxylation via the CYP3A4.52, 53Specific drug-drug interaction studies evaluating the clinical effects with CYP3A4 inducers or inhibitors on medroxyprogesterone acetate have not been conducted and therefore the clinical effects of CYP3A4 inducers or inhibitors are unknown.
The results of one study indicated that intramuscularly administered medroxyprogesterone acetate may induce or activate the CYP3A4 enzyme system, leading to an increased metabolism of many CYP3A4 substrates.
9.4 Drug-Drug Interactions
Aminoglutethimide: Aminoglutethimide administered concomitantly with DEPO-PROVERA (medroxyprogesterone acetate) may significantly depress the serum concentration of medroxyprogesterone acetate. Users of DEPO-PROVERA should be warned of the possibility of decreased efficacy with the use of this or any related drugs.
Rifampin: Rifampin can increase the metabolism of exogenously administered progestational agents. Norethindrone has specifically been affected; a reduction of plasma concentrations has occurred. The extent to which rifampin may alter the metabolism of other progestogens remains to be determined; the possibility of an interaction should be considered.
9.5 Drug-Food Interactions
Interactions with food have not been established.
9.6 Drug-Herb Interactions
Interactions with herbal products have not been established.
9.7 Drug-Laboratory Test Interactions
Certain endocrine and possibly liver function tests may be affected by treatment with DEPO-PROVERA. Therefore, if such tests are abnormal in a woman taking DEPO-PROVERA, it is recommended that they be repeated 6 to 12 months after the drug has been withdrawn.
The clinical chemist or pathologist should be advised of progestogen therapy when a woman’s blood or tissue specimens are submitted for laboratory diagnosis or biochemical analysis.
The following laboratory tests may be affected by the use of DEPO-PROVERA:
(a) Gonadotropin levels - inhibition of the midcycle LH surge
(b) Plasma progesterone levels - inhibition of ovulation and thus the postovulatory rise of progesterone
(c) Plasma estrogen levels - do not exceed early-to-mid-proliferative phase levels
(d) Plasma cortisol levels - not significantly affected by the dose used for contraception
(e) Glucose tolerance test - occasionally some degree of glucose intolerance may develop
(f) Plasma lipid concentrations - decrease in high density lipoprotein cholesterol (HDL-C) in some studies. The clinical relevance of this has yet to be determined
(g) Urinary pregnanediol levels (Note: DEPO-PROVERA does not interfere with the assay of human chorionic gonadotropin (HCG) either chemically or pharmacologically).