Progestins are hormones used to treat various forms of cancer.
These drugs include:
· hydroxyprogesterone caproate
· medroxyprogesterone acetate
· megestrol acetate.
When taken orally, megestrol acetate is well absorbed. After I.M. injection in an aqueous or oil suspension, hydroxyprogesterone caproate and medroxyprogesterone are absorbed slowly from their deposit sites.
These drugs are well distributed throughout the body and may se-quester in fatty tissue. Progestins are metabolized in the liver and excreted as metabolites in urine.
The mechanism of action of progestins in treating tumors isn’t completely understood. Researchers believe the drugs bind to a specific receptor to act on hormonally sensitive cells.
Because progestins don’t exhibit a cytotoxic activity (destroying or poisoning cells), they’re considered cytostatic (they keep the cells from multiplying).
Progestins are used for the palliative treatment of advanced en-dometrial, breast, prostate, and renal cancers. Of these drugs, megestrol is used most commonly.
No drug interactions have been identified for megestrol. However, other progestins do have significant interactions with other drugs.
· Barbiturates, carbamazepine, and rifampin reduce the progestin effects of hydroxyprogesterone.
· Hydroxyprogesterone and medroxyprogesterone may interfere with bromocriptine’s effects, causing menstruation to stop.
· Hydroxyprogesterone taken with dantrolene and other liver-toxic drugs increases the risk of liver toxicity.
· Dose adjustments in oral anticoagulants may be needed when they’re taken with hydroxyprogesterone.
· Aminoglutethimide and rifampin may reduce the progestin ef-fects of medroxyprogesterone. (See Adverse reactions to pro-gestins.)