Megestrol Tablets

• It is used to help raise feelings of hunger.
• It is used to treat endometrial or breast cancer.
• It may be given to you for other reasons. Talk with the doctor.

Megestrol acetate, is a synthetic, antineoplastic and progestational drug. Megestrol acetate USP is a white to creamy white, crystalline powder chemically designated as pregna-4,6-diene-3,20-dione, 17-(acetyloxy)-6-methyl-. Solubility at 37°C in water is 2 mcg per mL, solubility in plasma is 24 mcg per mL. Its molecular weight is 384.51. The empirical formula is C24 H32O4 and the structural formula is represented as follows:

Megestrol Acetate Tablets USP are supplied for oral administration containing 20 mg or 40 mg megestrol acetate USP. Each tablet contains the following inactive ingredients: acacia, colloidal silicon dioxide, dibasic calcium phosphate, lactose monohydrate, magnesium stearate and starch (corn).

While the precise mechanism by which megestrol produces its antineoplastic effects against endometrial carcinoma is unknown at the present time, inhibition of pituitary gonadotrophin production and resultant decrease in estrogen secretion may be factors. There is evidence to suggest a local effect as a result of the marked changes brought about by the direct instillation of progestational agents into the endometrial cavity. The antineoplastic action of megestrol acetate on carcinoma of the breast is effected by modifying the action of other steroid hormones and by exerting a direct cytotoxic effect on tumor cells. In metastatic cancer, hormone receptors may be present in some tissues but not others. The receptor mechanism is a cyclic process whereby estrogen produced by the ovaries enters the target cell, forms a complex with cytoplasmic receptor and is transported into the cell nucleus. There it induces gene transcription and leads to the alteration of normal cell functions. Pharmacologic doses of megestrol acetate not only decrease the number of hormone-dependent human breast cancer cells but also are capable of modifying and abolishing the stimulatory effects of estrogen on these cells. It has been suggested that progestins may inhibit in one of two ways: by interfering with either the stability, availability, or turnover of the estrogen receptor complex in its interaction with genes or in conjunction with the progestin receptor complex, by interacting directly with the genome to turn off specific estrogen-responsive genes.

There are several analytical methods used to estimate megestrol acetate plasma levels, including mass fragmentography, gas chromatography (GC), high pressure liquid chromatography (HPLC) and radioimmunoassay. The plasma levels by HPLC assay or radioimmunoassay methods are about one-sixth those obtained by the GC method. The plasma levels are dependent not only on the method used, but also on intestinal and hepatic inactivation of the drug, which may be affected by factors such as intestinal tract motility, intestinal bacteria, antibiotics administered, body weight, diet, and liver function.

Metabolites account for only 5% to 8% of the administered dose and are considered negligible. The major route of drug elimination in humans is the urine. When radiolabeled megestrol acetate was administered to humans in doses of 4 to 90 mg, the urinary excretion within 10 days ranged from 56.5% to 78.4% (mean 66.4%) and fecal excretion ranged from 7.7% to 30.3% (mean 19.8%). The total recovered radioactivity varied between 83.1% and 94.7% (mean 86.2%). Respiratory excretion as labeled carbon dioxide and fat storage may have accounted for at least part of the radioactivity not found in the urine and feces.

In normal male volunteers (n=23) who received 160 mg of megestrol acetate given as a 40 mg q.i.d. regimen, the oral absorption of megestrol acetate appeared to be variable. Plasma levels were assayed by a high pressure liquid chromatograpic (HPLC) procedure. Peak drug levels for the first 40 mg dose ranged from 10 to 56 ng/mL (mean 27.6 ng/mL) and the times to peak concentrations ranged from 1 to 3 hours (mean 2.2 hours). Plasma elimination half-life ranged from 13 to 104.9 hours (mean 34.2 hours). The steady state plasma concentrations for a 40 mg q.i.d. regimen have not been established.

History of hypersensitivity to megestrol acetate or any component of the formulation.

Weight Gain

Weight gain is a frequent side effect of megestrol. This gain has been associated with increased appetite and is not necessarily associated with fluid retention.

Thromboembolic Phenomena

Thromboembolic phenomena including thrombophlebitis and pulmonary embolism (in some cases fatal) have been reported.

Glucocorticoid Effects

See Warnings section.

Other Adverse Reactions

Heart failure, nausea and vomiting, edema, breakthrough menstrual bleeding, dyspnea, tumor flare (with or without hypercalcemia), hyperglycemia, glucose intolerance, alopecia, hypertension, carpal tunnel syndrome, mood changes, hot flashes, malaise, asthenia, lethargy, sweating and rash.

Breast Cancer: 160 mg/day (40 mg q.i.d.).

Endometrial Carcinoma: 40 mg/day to 320 mg/day in divided doses.

At least 2 months of continuous treatment is considered an adequate period for determining the efficacy of megestrol acetate.

Store at 20° to 25°C (68° to 77°F). [See USP Controlled Room Temperature.]

Protect from temperatures above 40°C (104°F).

Health Hazard Data

There is no threshold limit value established by OSHA, NIOSH, or ACGIH.

Exposure or “overdose” at levels approaching recommended dosing levels could result in side effects described above (see Warnings and Adverse Reactions sections). Women at risk of pregnancy should avoid such exposure.

Distr. by: West-Ward

Pharmaceuticals Corp.

Eatontown, NJ 07724

4056065//07

Revised May 2016