Antiandrogens, also known as androgen antagonists or testosterone blockers, are a class of drugs that prevent androgens like testosterone and dihydrotestosterone (DHT) from mediating their biological effects in the body. They act by blocking the androgen receptor (AR) and/or inhibiting or suppressing androgen production. They can be thought of as the functional opposites of AR agonists, for instance androgens and anabolic steroids (AAS) like testosterone, DHT, and nandrolone and selective androgen receptor modulators (SARMs) like enobosarm. Antiandrogens are one of three types of sex hormone antagonists, the others being antiestrogens and antiprogestogens.
Dihydrotestosterone is an endogenous androgen sex steroid and hormone primarily involved in the growth and repair of the prostate, the production of sebum, and body hair composition.
Finasteride, sold under the brand names Proscar and Propecia among others, is a medication used to treat pattern hair loss and benign prostatic hyperplasia (BPH) in men. It can also be used to treat excessive hair growth in women. It is usually taken orally but there are topical formulations for patients with hair loss, designed to minimize systemic exposure by acting specifically on hair follicles.
5α-Reductase inhibitors (5-ARIs), also known as dihydrotestosterone (DHT) blockers, are a class of medications with antiandrogenic effects which are used primarily in the treatment of enlarged prostate and scalp hair loss. They are also sometimes used to treat excess hair growth in women and as a component of hormone therapy for transgender women.
Flutamide, sold under the brand name Eulexin among others, is a nonsteroidal antiandrogen (NSAA) which is used primarily to treat prostate cancer. It is also used in the treatment of androgen-dependent conditions like acne, excessive hair growth, and high androgen levels in women. It is taken by mouth, usually three times per day.
Feminizing hormone therapy, also known as transfeminine hormone therapy, is hormone therapy and sex reassignment therapy to change the secondary sex characteristics of transgender people from masculine or androgynous to feminine. It is a common type of transgender hormone therapy and is used to treat transgender women and non-binary transfeminine individuals. Some, in particular intersex people but also some non-transgender people, take this form of therapy according to their personal needs and preferences.
Medrogestone, sold under the brand name Colprone among others, is a progestin medication which has been used in menopausal hormone therapy and in the treatment of gynecological disorders. It is available both alone and in combination with an estrogen. It is taken by mouth.
Allylestrenol, sold under the brand names Gestanin and Turinal among others, is a progestin medication which is used to treat recurrent and threatened miscarriage and to prevent premature labor in pregnant women. However, except in the case of proven progesterone deficiency, its use for such purposes is no longer recommended. It is also used in Japan to treat benign prostatic hyperplasia (BPH) in men. The medication is used alone and is not formulated in combination with an estrogen. It is taken by mouth.
Cyproterone acetate (CPA), sold alone under the brand name Androcur or with ethinylestradiol under the brand names Diane or Diane-35 among others, is an antiandrogen and progestin medication used in the treatment of androgen-dependent conditions such as acne, excessive body hair growth, early puberty, and prostate cancer, as a component of feminizing hormone therapy for transgender women, and in birth control pills. It is formulated and used both alone and in combination with an estrogen. CPA is taken by mouth one to three times per day.
Cyproterone, also known by its developmental code name SH-80881, is a steroidal antiandrogen which was studied in the 1960s and 1970s but was never introduced for medical use. It is an analogue of cyproterone acetate (CPA), an antiandrogen, progestin, and antigonadotropin which was introduced instead of cyproterone and is widely used as a medication. Cyproterone and CPA were among the first antiandrogens to be developed.
Delmadinone acetate (DMA), sold under the brand name Tardak among others, is a progestin and antiandrogen which is used in veterinary medicine to treat androgen-dependent conditions such as benign prostatic hyperplasia. It must be used with care as it has the potential to cause adrenal insufficiency via inhibition of adrenocorticotropic hormone (ACTH) secretion from the pituitary gland. DMA is the C17α acetate ester of delmadinone, which, in contrast to DMA, was never marketed for medical use.
Osaterone acetate, sold under the brand name Ypozane, is a medication which is used in veterinary medicine in Europe in the treatment of enlarged prostate in dogs. It is given by mouth.
Oxendolone, sold under the brand names Prostetin and Roxenone, is an antiandrogen and progestin medication which is used in Japan in the treatment of enlarged prostate. However, this use is controversial due to concerns about its clinical efficacy. Oxendolone is not effective by mouth and must be given by injection into muscle.
A nonsteroidal antiandrogen (NSAA) is an antiandrogen with a nonsteroidal chemical structure. They are typically selective and full or silent antagonists of the androgen receptor (AR) and act by directly blocking the effects of androgens like testosterone and dihydrotestosterone (DHT). NSAAs are used in the treatment of androgen-dependent conditions in men and women. They are the converse of steroidal antiandrogens (SAAs), which are antiandrogens that are steroids and are structurally related to testosterone.
Bifluranol is a synthetic nonsteroidal estrogen of the stilbestrol group related to diethylstilbestrol that has been used as an antiandrogen in the United Kingdom in the treatment of benign prostatic hyperplasia. It is a polyfluorinated biphenyl that is related to polybrominated and polychlorinated biphenyls and diethylstilbestrol. The drug is described as a weak estrogen, and possesses about one-eighth the potency of diethylstilbestrol.
BOMT, also known by its developmental code name Ro 7-2340 and as 6α-bromo-4-oxa-17α-methyl-5α-dihydrotestosterone, is a synthetic steroidal antiandrogen which was first developed in 1970 and was never marketed for medical use. It is the 6α-brominated, 4-oxygenated, and 17α-methylated derivative of the androgen dihydrotestosterone (DHT). Along with benorterone, cyproterone, and flutamide, BOMT was among the earliest antiandrogens to be developed and extensively studied, although it is less well-documented in comparison to the others. BOMT has been investigated clinically in the treatment of benign prostatic hyperplasia, though development for this use did not continue. There was also interest in BOMT for the potential applications of acne, pattern hair loss, and possibly prostate cancer, but it was not developed for these indications either.
Trimethyltrienolone (TMT), also known by its developmental code name R-2956 or RU-2956, is an antiandrogen medication which was never introduced for medical use but has been used in scientific research.
A steroidal antiandrogen (SAA) is an antiandrogen with a steroidal chemical structure. They are typically antagonists of the androgen receptor (AR) and act both by blocking the effects of androgens like testosterone and dihydrotestosterone (DHT) and by suppressing gonadal androgen production. SAAs lower concentrations of testosterone through simulation of the negative feedback inhibition of the hypothalamus. SAAs are used in the treatment of androgen-dependent conditions in men and women, and are also used in veterinary medicine for the same purpose. They are the converse of nonsteroidal antiandrogens (NSAAs), which are antiandrogens that are not steroids and are structurally unrelated to testosterone.
The pharmacology of bicalutamide is the study of the pharmacodynamic and pharmacokinetic properties of the nonsteroidal antiandrogen (NSAA) bicalutamide. In terms of pharmacodynamics, bicalutamide acts as a selective antagonist of the androgen receptor (AR), the biological target of androgens like testosterone and dihydrotestosterone (DHT). It has no capacity to activate the AR. It does not decrease androgen levels and has no other important hormonal activity. The medication has progonadotropic effects due to its AR antagonist activity and can increase androgen, estrogen, and neurosteroid production and levels. This results in a variety of differences of bicalutamide monotherapy compared to surgical and medical castration, such as indirect estrogenic effects and associated benefits like preservation of sexual function and drawbacks like gynecomastia. Bicalutamide can paradoxically stimulate late-stage prostate cancer due to accumulated mutations in the cancer. When used as a monotherapy, bicalutamide can induce breast development in males due to its estrogenic effects. Unlike other kinds of antiandrogens, it may have less adverse effect on the testes and fertility.
5α-Dihydroethisterone is an active metabolite of the formerly clinically used but now-discontinued progestin ethisterone and the experimental and never-marketed hormonal antineoplastic agent ethynylandrostanediol (HE-3235). Its formation from its parent drugs is catalyzed by 5α-reductase in tissues that express the enzyme in high amounts like the liver, skin, hair follicles, and prostate gland. 5α-DHET has significant affinity for steroid hormone receptors and may contribute importantly to the activities of its parent drugs.
