Overview
Finasteride is a synthetic 4-azasteroid compound that acts as a competitive inhibitor of Type II 5α-reductase, an intracellular enzyme that converts testosterone to dihydrotestosterone (DHT). It is used primarily for the treatment of symptomatic benign prostatic hyperplasia (BPH) and male pattern hair loss (androgenetic alopecia).
Mechanism of Action
Finasteride inhibits Type II 5α-reductase, blocking the conversion of testosterone to dihydrotestosterone (DHT) in target tissues. This reduces serum and tissue DHT levels, leading to decreased prostate volume in BPH and reduced hair follicle miniaturization in androgenetic alopecia.
Indications
- Treatment of symptomatic benign prostatic hyperplasia (BPH) to improve symptoms and reduce the risk of acute urinary retention and need for surgery
- Treatment of male pattern hair loss (androgenetic alopecia) in men only
Dosage
For BPH: 5 mg orally once daily. For male pattern hair loss: 1 mg orally once daily. Both formulations should be taken with or without food. Clinical response may require 6 months or more of treatment for BPH.
Contraindications
- Hypersensitivity to finasteride or any component of the formulation
- Pregnancy (Category X) - risk of fetal abnormalities
- Women who are or may become pregnant
- Children
Side Effects
- Decreased libido
- Erectile dysfunction
- Ejaculation disorder
- Breast tenderness and enlargement
- Skin rash
- Depression
- Dizziness
- Headache
Interactions
- No clinically significant drug interactions have been identified
- Theoretically could interact with other 5α-reductase inhibitors, but clinical significance unknown