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Pharmacology: Pharmacodynamics: Finasteride is a synthetic 4-azasteroid compound, competitively and specifically inhibits 5α-reductase (type II), an isoenzyme that metabolizes testosterone into dihydrotestosterone (DHT).
1 mg: The inhibition blocks the peripheral conversion of testosterone to DHT, leading to significant reduction in serum and tissue DHT. Finasteride increases hair growth and slows hair loss.
5 mg: DHT is the potent androgen responsible for the development and enlargement of the prostate gland. In benign prostatic hyperplasia (BPH), Finasteride decreases serum and tissue DHT. Finasteride had no affinity for the androgen receptor.
Pharmacokinetics: Food does not affect the bioavailability of Finasteride. It is about 90% bound to plasma protein. Finasteride crosses the blood-brain barrier. It is metabolized in the liver, primarily by the cytochrome P450 CYP3A4, and excreted in urine (39%) and feces (57%) as metabolites.
1 mg: The mean bioavailability of Finasteride was 65%.
5 mg: The mean bioavailability of Finasteride was 63%.
