Mechanisms of antiandrogen action
Pharmacological agents of this group exert their effects through two main pathways:
- Disruption of androgen hormone synthesis in the body.
- Direct blockade of androgen binding to sensitive receptors.
The selectivity of these agents' effects is strictly limited to tissues where hormonal activity is mediated predominantly by dihydrotestosterone. The main targets for their action are the prostate gland and external genitalia.
Androgen synthesis inhibitors
A prominent representative of synthesis inhibitors is Finasteride (known under the trade name Proscar).
- Pharmacodynamics: the drug selectively inhibits the enzyme $5\alpha$-reductase, and its action is tissue-specific, manifesting in the prostate gland.
- Chain of effects: blockade of the enzyme leads to impaired conversion of testosterone into active dihydrotestosterone $\rightarrow$ reduced stimulation of prostate cell proliferation $\rightarrow$ a decrease in overall gland size.
- Administration: the drug is taken orally (per os) and is the primary agent for the treatment of benign prostatic hyperplasia (BPH).
Classification of receptor blockers
Drugs that block androgen receptors are divided into two main groups. Their categorization is based on chemical structure features and the specific mechanism of interaction with the body's cellular receptors.
Briefly: answers to topical questions
What are the two groups into which androgen receptor blockers are divided?
Androgen receptor blockers are divided into two groups depending on their chemical structure and mechanism of interaction with receptors. Based on this classification, the following main groups of drugs are distinguished:
- Steroid drugs — derivatives of progesterone.
- Non-steroidal competitive antagonists — synthetic non-steroidal antiandrogens that compete with natural hormones for binding to receptors in target organs.
Which drugs belong to steroid antiandrogens?
Steroid antiandrogenic drugs include cyproterone, a progesterone derivative.
- Cyproterone (Cyproterone) is a steroid drug. It is a partial agonist of androgen receptors with antiandrogenic activity, suppresses the secretion of pituitary gonadotropic hormones, and reduces the effects of androgens in tissues.
Which drugs belong to non-steroidal antiandrogens?
The group of synthetic non-steroidal antiandrogens includes competitive antagonists used for the treatment of prostate cancer. This group includes the following drugs:
- Flutamide (Flutamide) — competitively blocks androgen binding to receptors and suppresses the inhibitory effect of testosterone on gonadotropin secretion.
- Bicalutamide (Bicalutamide) — a non-steroidal competitive antagonist that blocks androgen binding.
- Nilutamide — a synthetic non-steroidal antiandrogen.
FINAsteride: FINA-lizes (reduces) the prostate by blocking 5-alpha-reductase and the conversion of testosterone to dihydrotestosterone.
Class and exam questions
What are the two main mechanisms of action of antiandrogen drugs?
Drugs act by disrupting the synthesis of androgen hormones or by blocking the binding of androgens to cellular receptors.
Which enzyme does finasteride inhibit, and what is its localization?
Finasteride inhibits the enzyme 5α-reductase, and its action is tissue-specific, manifesting in the prostate gland.
What is the primary indication for the use of finasteride?
The primary indication is benign prostatic hyperplasia (BPH); the drug is taken orally.
What else to study on this topic
- Detailed analysis of the clinical pharmacology of Cyproterone
- Study of the two groups of androgen receptor blockers by chemical structure
- Use of the antiestrogen clomifene in anovulatory infertility
- Use of the gonadotropin synthesis inhibitor danazol in endometriosis
- Peculiarities of thiamazole use in hyperthyroidism
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