Antiandrogen

Antiandrogen

Antiandrogen MDV3100

• Antiandrogens are a class of drugs that inhibit the effects of androgen hormones, such as testosterone and dihydrotestosterone (DHT), in the body.
• Androgens play a crucial role in the development and maintenance of male sexual characteristics and are also involved in the growth and function of certain tissues.
• Antiandrogens are used in the treatment of various conditions related to androgen excess or androgen-dependent diseases.

Mechanisms of Action

• Antiandrogens exert their effects through different mechanisms, including:

Competitive Androgen Receptor (AR) Antagonism:

• Antiandrogens compete with androgens for binding to the androgen receptor, which is present in target tissues.
• By occupying the receptor, antiandrogens block the binding of endogenous androgens and prevent their activation of target genes, thereby inhibiting androgen signaling.

Inhibition of Androgen Synthesis:

• Some antiandrogens, such as cyproterone acetate and abiraterone, work by inhibiting the production of androgens.
• They target enzymes involved in the synthesis of androgens, such as 5-alpha reductase or cytochrome P450 enzymes, reducing the overall androgen levels in the body.

Suppression of Gonadal Function:

• Antiandrogens can also act by suppressing gonadal function, either directly or indirectly.
• For example, gonadotropin-releasing hormone (GnRH) analogs, such as leuprolide or goserelin, inhibit the release of luteinizing hormone (LH), which in turn reduces the production of testosterone by the testes.

Types of Antiandrogens

There are different types of antiandrogens used in medical practice, including:

Nonsteroidal Antiandrogens:

• Drugs such as bicalutamide, enzalutamide, and flutamide belong to this class.
• They exert their antiandrogenic effects by competitively binding to the androgen receptor, blocking the activation of target genes.

Steroidal Antiandrogens:

• Cyproterone acetate and spironolactone are examples of steroidal antiandrogens.
• They possess both antiandrogenic and progestational or anti-mineralocorticoid properties.

5-Alpha Reductase Inhibitors:

• Finasteride and dutasteride are commonly used 5-alpha reductase inhibitors.
• They inhibit the enzyme 5-alpha reductase, which converts testosterone to its more potent form, dihydrotestosterone (DHT).

GnRH Analogues:

• Gonadotropin-releasing hormone analogues, such as leuprolide and goserelin, suppress the release of luteinizing hormone (LH), which leads to decreased testosterone production by the testes.

Examples of antiandrogens

• Bicalutamide: Bicalutamide is a nonsteroidal antiandrogen commonly used in the treatment of prostate cancer. It competitively binds to the androgen receptor, blocking the action of androgens.

• Flutamide: Flutamide is another nonsteroidal antiandrogen used in the treatment of prostate cancer. It acts by blocking androgen receptors in target tissues.

• Cyproterone acetate: Cyproterone acetate is a steroidal antiandrogen that is used in the treatment of conditions such as hirsutism, acne, and androgenetic alopecia. It also possesses progestational activity and is used in hormone replacement therapy for transgender women.

• Spironolactone: Spironolactone is a medication with antiandrogenic effects that is primarily used as a diuretic. It is also prescribed in the treatment of conditions such as hirsutism, acne, and androgenetic alopecia in women.

• Finasteride: Finasteride is a 5-alpha reductase inhibitor that is commonly used in the treatment of benign prostatic hyperplasia (BPH) and male-pattern baldness (androgenetic alopecia). It inhibits the enzyme 5-alpha reductase, which converts testosterone to its more potent form, dihydrotestosterone (DHT).

• Dutasteride: Dutasteride is another 5-alpha reductase inhibitor used in the treatment of BPH. It inhibits both type I and type II 5-alpha reductase enzymes, resulting in a reduction in DHT levels.

• These are just a few examples of antiandrogens, and there are other drugs available in this class with varying mechanisms of action and indications.
• The specific choice of antiandrogen depends on the condition being treated and individual patient factors, and it should always be prescribed by a healthcare professional.

Indications

Antiandrogens have various medical indications, including:

• Prostate Cancer: Antiandrogens are used in the treatment of prostate cancer, either as a monotherapy or in combination with other treatments. By blocking androgen receptor signaling or reducing androgen levels, antiandrogens can slow down the growth of prostate cancer cells.

• Hirsutism: Antiandrogens, such as spironolactone, can be used to manage excessive hair growth (hirsutism) in women. They inhibit the effects of androgens on hair follicles, leading to a reduction in hair growth.

• Androgenetic Alopecia: Some antiandrogens, such as finasteride, are used to treat male-pattern baldness (androgenetic alopecia) by inhibiting the conversion of testosterone to DHT, which is implicated in hair follicle miniaturization.

• Polycystic Ovary Syndrome (PCOS): Antiandrogens may be prescribed to manage symptoms of PCOS, such as acne, hirsutism, and irregular menstrual cycles. By reducing androgen activity, antiandrogens can help alleviate these symptoms.

Adverse Effects

• The use of antiandrogens can be associated with certain adverse effects, which can vary depending on the specific drug and individual factors.

Some common adverse effects include:

• Hormonal Imbalances: Antiandrogens can disrupt the hormonal balance in the body, leading to side effects such as changes in libido, mood swings, and menstrual irregularities.
• Gastrointestinal Effects: Some antiandrogens, particularly those taken orally, can cause gastrointestinal disturbances such as nausea, vomiting, or diarrhea.
• Liver Toxicity: Certain antiandrogens, like flutamide, can rarely cause liver toxicity. Regular liver function tests may be necessary during treatment.
• Cardiovascular Effects: Some antiandrogens may have cardiovascular effects, including an increased risk of blood clots or cardiovascular events. Close monitoring of cardiovascular health is important during treatment.

Drug Interactions

• Antiandrogens may interact with other medications, potentially affecting their efficacy or increasing the risk of adverse effects.

Some examples of drug interactions include:

• Warfarin: Some antiandrogens, such as bicalutamide, may interfere with the metabolism of warfarin, an oral anticoagulant. Close monitoring of prothrombin time and international normalized ratio (INR) is necessary when these drugs are used together.
• Digoxin: Certain antiandrogens, like spironolactone, can increase the serum levels of digoxin, a medication used for heart conditions.

See Also

• Androgen
• Prostate Cancer
• Hirsutism
• Polycystic Ovary Syndrome (PCOS)
• Gonadotropin-Releasing Hormone (GnRH) Analog
• Testosterone
• Antiandrogen Therapy in Prostate Cancer
• Male-Pattern Baldness (Androgenetic Alopecia)
• Endocrine System
• Pharmacology

References

• Mohler, M. L., Bohl, C. E., Jones, A., Coss, C. C., Narayanan, R., He, Y., ... & Dalton, J. T. (2009). Nonsteroidal selective androgen receptor modulators (SARMs): dissociating the anabolic and androgenic activities of the androgen receptor for therapeutic benefit. Journal of medicinal chemistry, 52(12), 3597-3617.
• Freedberg, I. M., Eisen, A. Z., Wolff, K., Austen, K. F., Goldsmith, L. A., Katz, S. I., & Fitzpatrick, T. B. (Eds.). (2003). Fitzpatrick's Dermatology in General Medicine (6th ed.). McGraw-Hill.
• Crawford, E. D., Heidenreich, A., Lawrentschuk, N., Tombal, B., Pompeo, A. C. L., Mendoza-Valdes, A., ... & Shore, N. (2017). Androgen-targeted therapy in men with prostate cancer: evolving practice and future considerations. Prostate cancer and prostatic diseases, 20(4), 361-379.
• Arlt, W., & Auchus, R. J. (Eds.). (2018). Androgen Excess Disorders in Women: Polycystic Ovary Syndrome and Other Disorders (2nd ed.). Springer International Publishing.

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