Mechanisms of Action of Antiandrogens
Pharmacological agents in this group exert their effects through two primary pathways:
- Disruption of androgen hormone synthesis in the body.
- Direct blockade of androgen binding to sensitive receptors.
The selectivity of these agents is strictly limited to tissues where hormonal activity is driven primarily by dihydrotestosterone. The main targets for their action are the prostate gland and external genitalia.
Androgen Synthesis Inhibitors
A prominent example of a synthesis inhibitor is finasteride (known under the brand name Proscar).
- Pharmacodynamics: The drug selectively inhibits the enzyme $5\alpha$-reductase, and its action is tissue-specific, taking place in the prostate gland.
- Chain of effects: Enzyme blockade leads to impaired conversion of testosterone into active dihydrotestosterone $\rightarrow$ decreased stimulation of prostate cell proliferation $\rightarrow$ reduction in overall prostate volume.
- Administration: The drug is taken orally (per os) and is a primary treatment for 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.