Medroxyprogesterone Acetate

MEDROXYPROGESTERONE ACETATE- medroxyprogesterone acetate tablet
Avera McKennan Hospital

WARNING: CARDIOVASCULAR DISORDERS, BREAST CANCER AND PROBABLE DEMENTIA FOR ESTROGEN PLUS PROGESTIN THERAPY

Cardiovascular Disorders and Probable Dementia

Estrogen plus progestin therapy should not be used for the prevention of cardiovascular disease or dementia. (See CLINICAL STUDIES and WARNINGS, Cardiovascular Disorders and Probable Dementia.)

The Women’s Health Initiative (WHI) estrogen plus progestin substudy reported an increased risk of deep vein thrombosis (DVT), pulmonary embolism (PE), stroke and myocardial infarction (MI) in postmenopausal women (50 to 79 years of age) during 5.6 years of treatment with daily oral conjugated estrogens (CE) [0.625] mg combined with medroxyprogesterone acetate (MPA) [2.5 mg], relative to placebo. (See CLINICAL STUDIES and WARNINGS, Cardiovascular Disorders.)

The WHI Memory Study (WHIMS) estrogen plus progestin ancillary study reported an increased risk of developing probable dementia in postmenopausal women 65 years of age or older during 4 years of treatment with daily CE (0.625 mg) combined with MPA (2.5 mg), relative to placebo. It is unknown whether this finding applies to younger postmenopausal women. (See CLINICAL STUDIES and WARNINGS, Probable Dementia and PRECAUTIONS, Geriatric Use.)

Breast Cancer

The WHI estrogen plus progestin substudy demonstrated an increased risk of invasive breast cancer. (See CLINICAL STUDIES and WARNINGS, Malignant Neoplasm, Breast Cancer. )

In the absence of comparable data, these risks should be assumed to be similar for other doses of CE and MPA, and other combinations and dosage forms of estrogens and progestins.

Progestins with estrogens should be prescribed at the lowest effective doses and for the shortest duration consistent with treatment goals and risks for the individual woman.

DESCRIPTION

Medroxyprogesterone acetate tablets contain medroxyprogesterone acetate, which is a derivative of progesterone. It is a white to off-white, odorless crystalline powder, stable in air, melting between 200 and 210°C. It is freely soluble in chloroform, soluble in acetone and in dioxane, sparingly soluble in alcohol and in methanol, slightly soluble in ether, and insoluble in water.

The chemical name for medroxyprogesterone acetate is pregn-4-ene-3, 20-dione, 17-(acetyloxy)-6-methyl-, (6α)-. The structural formula is:

Chemical Structure
(click image for full-size original)

Each medroxyprogesterone acetate tablet for oral administration contains 2.5 mg, 5 mg or 10 mg of medroxyprogesterone acetate and the following inactive ingredients: calcium stearate, corn starch, lactose, mineral oil, sorbic acid, sucrose, and talc. The 2.5 mg tablet contains FD&C Yellow No. 6.

CLINICAL PHARMACOLOGY

Medroxyprogesterone acetate (MPA) administered orally or parenterally in the recommended doses to women with adequate endogenous estrogen, transforms proliferative into secretory endometrium. Androgenic and anabolic effects have been noted, but the drug is apparently devoid of significant estrogenic activity. While parenterally administered MPA inhibits gonadotropin production, which in turn prevents follicular maturation and ovulation, available data indicate that this does not occur when the usually recommended oral dosage is given as single daily doses.

Pharmacokinetics

The pharmacokinetics of MPA were determined in 20 postmenopausal women following a single-dose administration of eight MPA 2.5 mg tablets or a single administration of two MPA 10 mg tablets under fasting conditions. In another study, the steady-state pharmacokinetics of MPA were determined under fasting conditions in 30 postmenopausal women following daily administration of one MPA 10 mg tablet for 7 days. In both studies, MPA was quantified in serum using a validated gas chromatography-mass spectrometry (GC-MS) method. Estimates of the pharmacokinetic parameters of MPA after single and multiple doses of MPA tablets were highly variable and are summarized in Table 1.

Table 1. Mean (SD) Pharmacokinetic Parameters for Medroxyprogesterone Acetate (MPA)
Tablet Strength C max (ng/mL) T max (h) Auc 0–(∞) (ng∙h/mL) t 1/2 (h) Vd/f(L) CL/f(mL/min)
*
Following Day 7 dose
Single Dose
2 × 10 mg 1.01 (0.599) 2.65 (1.41) 6.95 (3.39) 12.1 (3.49) 78024(47220) 64110(42662)
8 × 2.5 mg 0.805 (0.413) 2.22 (1.39) 5.62 (2.79) 11.6 (2.81) 62748(40146) 74123(35126)
Multiple Dose
10 mg * 0.71 (0.35) 2.83 (1.83) 6.01 (3.16) 16.6 (15.0) 40564(38256) 41963(38402)

A. Absorption

No specific investigation on the absolute bioavailability of MPA in humans has been conducted. MPA is rapidly absorbed from the gastrointestinal tract, and maximum MPA concentrations are obtained between 2 to 4 hours after oral administration.

Administration of MPA with food increases the bioavailability of MPA. A 10 mg dose of MPA, taken immediately before or after a meal, increased MPA Cmax (50 to 70%) and AUC (18 to 33%). The half-life of MPA was not changed with food.

B. Distribution

MPA is approximately 90% protein bound, primarily to albumin; no MPA binding occurs with sex hormone binding globulin.

C. Metabolism

Following oral dosing, MPA is extensively metabolized in the liver via hydroxylation, with subsequent conjugation and elimination in the urine.

D. Excretion

Most MPA metabolites are excreted in the urine as glucuronide conjugates with only minor amounts excreted as sulfates.

E. Specific Populations

Hepatic Insufficiency

MPA is almost exclusively eliminated via hepatic metabolism. In 14 patients with advanced liver disease, MPA disposition was significantly altered (reduced elimination). In patients with fatty liver, the mean percent dose excreted in the 24-hour urine as intact MPA after a 10 mg or 100 mg dose was 7.3% and 6.4%, respectively.

Renal Insufficiency

The effect of renal impairment on the pharmacokinetics of MPA has not been studied.

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