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Finasteride (Finasteride (Propecia/Proscar))

Category: Hair Growth. Status: FDA Approved (hair loss & BPH).

The first-line FDA-approved treatment for male pattern hair loss. Selectively inhibits type II 5-alpha reductase, reducing scalp DHT levels by ~60-70% to slow or reverse follicular miniaturization.

How it works

Selectively inhibits type II 5-alpha reductase (predominant in hair follicles), reducing conversion of testosterone to dihydrotestosterone. Serum DHT decreases ~70%, scalp DHT ~40%, allowing follicle recovery.

Key facts

  • Molecular weight: 372.54 Da
  • Half-life: ~6-8 hours (but DHT suppression lasts 24h)
  • Bioavailability: ~80% oral
  • Storage: Room temperature. Do not handle crushed tablets if pregnant.

Dosing overview

  • Typical dose: 1 mg (hair) or 5 mg (prostate)
  • Frequency: Daily
  • Duration: 12+ months for full assessment
  • Route: Oral tablet

Reported benefits

  • Halts hair loss progression (90% of men)
  • Regrows hair (65% of men)
  • Well-studied long-term safety
  • FDA-approved
  • Available generic
  • Topical option available

Possible side effects

  • Decreased libido (2-3%)
  • Erectile dysfunction (1-2%)
  • Decreased ejaculate volume
  • Gynecomastia (rare)
  • Depression (rare)

Research

  • Finasteride 10-year follow-up (2019): 10-year data showed 86% of treated men maintained or improved hair counts, with only 14% showing continued loss.
  • Topical vs oral finasteride (2022): Topical finasteride 0.25% achieved equivalent hair counts to oral 1mg with 50% less systemic DHT suppression, reducing side effect risk.

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Research and educational reference only. Not medical advice.