Antiandrogen
An antiandrogen, or androgen antagonist, is any of a group of hormone antagonist compounds that are capable of preventing or inhibiting the biologic effects of androgens, male sex hormones, on normally responsive tissues in the body (see androgen insensitivity syndrome). Antiandrogens usually work by blocking the appropriate receptors, competing for binding sites on the cell's surface, literally obstructing the androgens' pathway.
Antiandrogens are often indicated to treat severe male sexual disorders, such as hypersexuality (excessive sexual desire) and sexual deviation, specifically paraphilias, as well as use as a antineoplastic agent and palliative, adjuvant or neoadjuvant hormonal therapy in prostate cancer.
Antiandrogens can also be used for treatment of benign prostatic hyperplasia (prostate enlargement), acne, androgenetic alopecia (male pattern baldness), and hirsutism (excessive hairiness). They are also occasionally used as a male contraceptive agent, to purposefully prevent or counteract masculinisation in the case of male to female transsexuals, and to prevent the symptoms associated with reduced testosterone, like hot flashes, following castration.
The administration of antiandrogens in males can result in slowed or halted development or reversal of male secondary sex characteristics, reduced activity or function of the accessory male sex organs, and hyposexuality (diminished sexual desire or libido).
The term antiandrogen withdrawal response (AAWR) describes the medical course taken when cancer cells adapt to feed on the antiandrogens rather than androgen, so that treatment must be halted in order to starve those cells thriving on the antiandrogens.
Currently available antiandrogen drugs (brand names in parentheses) include:
- Bicalutamide (Casodex), A nonsteroidal antiandrogen, administered orally, used in combination with a luteinizing hormone-releasing hormone (LHRH) agonist in treatment of prostate cancer
- Cyproterone acetate (Androcur), a synthetic steroid, a potent antiandrogen that also possesses progestational properties
- Finasteride (Proscar, Propecia), a synthetic enzyme inhibitor, known as a 5-α-reductase (type II) inhibitor, that prevents dihydrotestosterone synthesis, administered orally, mainly used for treatment of benign prostate enlargement and as a hair growth stimulant
- Dutasteride (Avodart), a newer 5α-reductase inhibitor, that also blocks 5α-reductase type I
- Flutamide (Eulexin), a nonsteroidal androgen receptor blocker used to treat hirsutism and metastatic prostate cancer, and to increase the flow of urine in benign prostate enlargement
- Ketoconazole (Nizoral), an imidazole derivative used as a broad-spectrum antifungal agent effective against a variety of fungal infections, side effects include serious liver damage and reduced levels of androgen from both the testicles and adrenal glands
- Nilutamide (Anandron, Nilandron), a nonsteroidal antiandrogen used as an antineoplastic agent in treatment of prostate cancer
- Spironolactone (Aldactone, Spiritone), a synthetic 17-spirolactone corticosteroid, which is a renal competitive aldosterone antagonist in a class of pharmaceuticals called potassium-sparing diuretics, used primarily to treat low-rennin hypertension, hypokalemia, and Conn's syndrome
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