Megestrol is a synthetic steroid, a derivative of chlormadinone. It possesses progestogenic and antigonadotropic properties, but does not exhibit androgenic or estrogenic activity. It inhibits ovulation. Megestrol acetate is used in the treatment of hormone-dependent breast and endometrial cancers. Megestrol reduces or inhibits the stimulatory effects of estrogens on receptors and also exerts a direct cytotoxic effect on tumor cells. It increases body weight by stimulating appetite and promoting the growth of adipose and muscle tissue.
Megestrol is well absorbed after oral administration. However, its gastrointestinal absorption depends on intestinal peristalsis, commensal flora, patient body weight, diet, and concomitant use of other medications.
Megestrol may accumulate in adipose tissue.
The liver is primarily responsible for the metabolism of megestrol, producing active metabolites. Megestrol acetate exhibits activity at androgen and glucocorticoid receptors, while its metabolites are active at progesterone receptors.
The mean elimination half-life of megestrol acetate is 34.2 hours. Approximately 66% of the substance is excreted renally and approximately 20% in feces. The portion of the drug not excreted renally or into the gastrointestinal lumen is eliminated via the respiratory system or stored in adipose tissue.
⚠️ Warnings
Megestrol must not be used in pregnant women due to the risk of fetal harm, particularly during the first months of pregnancy. Women of childbearing potential should use effective contraception while taking this medication. Megestrol should also be avoided in breastfeeding women. Due to a minimally increased risk of breast cancer, regular check-ups should be recommended for patients taking megestrol. In patients with diabetes mellitus, increased insulin requirements may occur during megestrol therapy. Particular caution should also be exercised in patients with thrombophlebitis. Both the use and discontinuation of megestrol may slightly suppress adrenal function. Particularly in cases of abrupt discontinuation, patients should be monitored for symptoms such as hypotension, dizziness, nausea, or vomiting.
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