Finasteride

Category: hormone

Aliases: Propecia, Proscar, MK-906

Pharmacological Mechanism

4-Azasteroid competitive inhibitor of 5α-reductase type II (dominant in prostate, seminal vesicles, scalp follicles). Blocks conversion of testosterone → dihydrotestosterone (DHT). ~70% serum DHT suppression at 1 mg/d; higher suppression at 5 mg in prostatic tissue. Does not affect testosterone or estradiol levels. Does not cover type I isoform (sebum, liver) — dutasteride inhibits both.

Half-Life (t½)

PO: 6h

Dosing Guidelines

• PO: Typical 1mg (Range: 1 - 1 mg)

Target Organ Systems

• endocrine
• reproductive
• integumentary

Interactions

• Testosterone (TRT)
• Dutasteride