Finasteride

Updated: 2026-09-16

Overview

Finasteride is a synthetic 4-azasteroid medication first approved by the FDA in 1992. It was developed by Merck & Co. under the brand names Proscar (for BPH) and Propecia (for hair loss). As a competitive inhibitor of Type II 5α-reductase, it disrupts the conversion of testosterone to dihydrotestosterone (DHT), a hormone linked to prostate growth and hair follicle miniaturization. Its clinical efficacy is well-documented, with studies showing a 50-60% reduction in prostate volume for BPH patients and improved hair count in 80% of male pattern baldness cases after 6-12 months of use. The drug is typically administered orally in 1mg (for alopecia) or 5mg (for BPH) doses.

Physical and Chemical Properties

Finasteride is a white crystalline powder with moderate lipophilicity (logP ~3.0), contributing to its good membrane permeability. It exhibits stability under normal storage conditions but may degrade upon prolonged exposure to UV light or high humidity. The compound has two polymorphic forms (Form I and Form II), with Form I being the commercially used variant. Its poor water solubility (0.03 mg/mL at 25°C) necessitates formulation with solubilizing agents for oral bioavailability. The molecule contains a lactam group (C=O-N) and a steroidal backbone, making it structurally distinct from non-steroidal anti-androgens.

Main Applications

In urology, finasteride 5mg tablets are first-line therapy for moderate benign prostatic hyperplasia (BPH), often combined with alpha-blockers. It reduces prostate volume by 20-30% within 6 months, alleviating urinary obstruction symptoms. In dermatology, the 1mg formulation is prescribed for androgenetic alopecia in men, with visible hair regrowth typically appearing after 3-6 months of daily use. Off-label applications include hirsutism management and preoperative reduction of bleeding in transurethral prostate resection. Veterinary use for canine prostatic diseases is also documented.

Safety and Storage

Finasteride is classified as pregnancy category X due to risk of fetal abnormalities if absorbed through skin or mucous membranes. Pharmacists and handlers should use gloves when processing bulk powder. Proper storage requires airtight containers with desiccants, maintaining temperature below 25°C. Degradation products may include oxidation byproducts and lactam ring-opened forms. Shelf life typically exceeds 24 months when stored correctly. Disposal should follow pharmaceutical waste guidelines to prevent environmental contamination.

B2B Procurement Guide

Bulk pharmaceutical buyers should prioritize suppliers with WHO-GMP or EU-GMP certification. Key quality parameters include HPLC purity ≥98%, low heavy metal content (<10ppm), and absence of genotoxic impurities. For formulation manufacturers, particle size distribution (D90 <50μm) and polymorphic consistency are critical for tablet compression. Large-volume purchasers (100kg+) can negotiate prices down to $40-80/kg. Always request Certificate of Analysis (CoA), DMF/ASMF references, and stability study data. Consider suppliers with dual sourcing capabilities to mitigate supply chain risks.