Megestrol acetate

Megestrol acetate (MGA), sold under the brand name Megace among others, is a progestin medication which is used mainly as an appetite stimulant to treat wasting syndromes such as cachexia. It is also used to treat breast cancer and endometrial cancer, and has been used in birth control. Megestrol acetate is generally formulated alone, although it has been combined with estrogens in birth control formulations. It is usually taken by mouth.

Megestrol acetate
Clinical data
Trade namesMegace, others
Other namesMGA; BDH-1298; NSC-71423; SC-10363; 17α-Acetoxy-6-dehydro-6-methylprogesterone; 17α-Acetoxy-6-methylpregna-4,6-diene-3,20-dione
License data
Routes of
administration		By mouth
Drug classProgestogen; Progestin; Progestogen ester; Antigonadotropin; Steroidal antiandrogen
ATC code
Legal status
Legal status
  • US: ℞-only
  • In general: ℞ (Prescription only)
Pharmacokinetic data
Bioavailability100%
Protein binding82% to albumin, no affinity for SHBGTooltip sex hormone-binding globulin or CBGTooltip corticosteroid-binding globulin
MetabolismLiver (hydroxylation, reduction, conjugation)
Elimination half-lifeMean: 34 hours
Range: 13–105 hours
ExcretionUrine: 57–78%
Feces: 8–30%
Identifiers
  • [(8R,9S,10R,13S,14S,17R)-17-acetyl-6,10,13-trimethyl-3-oxo-2,8,9,11,12,14,15,16-octahydro-1H-cyclopenta[a]phenanthren-17-yl] acetate
CAS Number
PubChem CID
DrugBank
ChemSpider
UNII
KEGG
ChEBI
CompTox Dashboard (EPA)
ECHA InfoCard100.008.969
Chemical and physical data
FormulaC24H32O4
Molar mass384.516 g·mol−1
3D model (JSmol)
  • CC1=C[C@@H]2[C@H](CC[C@]3([C@H]2CC[C@@]3(C(=O)C)OC(=O)C)C)[C@@]4(C1=CC(=O)CC4)C
  • InChI=1S/C24H32O4/c1-14-12-18-19(22(4)9-6-17(27)13-21(14)22)7-10-23(5)20(18)8-11-24(23,15(2)25)28-16(3)26/h12-13,18-20H,6-11H2,1-5H3/t18-,19+,20+,22-,23+,24+/m1/s1
  • Key:RQZAXGRLVPAYTJ-GQFGMJRRSA-N

Side effects of megestrol acetate include increased appetite, weight gain, vaginal bleeding, nausea, edema, low sex hormone levels, sexual dysfunction, osteoporosis, cardiovascular complications, glucocorticoid effects, and others. Megestrol acetate is a progestin, or a synthetic progestogen, and hence is an agonist of the progesterone receptor, the biological target of progestogens like progesterone. It has weak partial androgenic activity, weak glucocorticoid activity, and no other important hormonal activity. Due to its progestogenic activity, megestrol acetate has antigonadotropic effects. The mechanism of action of the appetite stimulant effects of megestrol acetate is unknown.

Megestrol acetate was discovered in 1959 and was introduced for medical use, specifically in birth control pills, in 1963. It may be considered a "first-generation" progestin. The medication was withdrawn in some countries in 1970 due to concerns about mammary toxicity observed in dogs, but this turned out not to apply to humans. Megestrol acetate was approved for the treatment of endometrial cancer in 1971 and wasting syndromes in 1993. It is marketed widely throughout the world. It is available as a generic medication.

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