Finasteride and dutasteride are the most effective medications against androgenetic alopecia. Yet their mechanism, comparative efficacy, and side effects remain poorly understood. A complete, evidence-based guide.
Why DHT Causes Hair Loss
Androgenetic alopecia is caused by follicle sensitivity to dihydrotestosterone (DHT), derived from testosterone via the enzyme 5-alpha-reductase (5aR). DHT causes progressive miniaturization of genetically sensitive follicles until complete extinction. 5aR inhibitors block this conversion and reduce scalp DHT levels.
Finasteride (Propecia): Mechanism and Efficacy
Finasteride 1mg selectively inhibits 5aR type II, responsible for 60-70% of follicular DHT production. It reduces serum DHT by approximately 65-70%.
- Stops or slows hair loss in 83-90% of cases
- Visible regrowth in 60-65% of patients after 2 years
- Optimal results after 12-24 months of continuous treatment
- Most effective on the vertex (crown) and midline frontal zone
FDA-approved since 1997. Prescribed for nearly 30 years with a well-established safety profile.
Dutasteride (Avodart): More Powerful
Dutasteride 0.5mg inhibits both isoforms of 5-alpha-reductase (types I AND II), reducing DHT levels by 90-95% — 25 to 30 percentage points more than finasteride.
- Superior to finasteride in regrowth in direct comparative studies
- Visible results faster (6-9 months vs 12 months)
- Particularly suited for rapidly progressive cases (Norwood IV-VI)
- Much longer half-life (5 weeks vs 6 hours)
Side Effects: Reality vs Perception
Clinical trial data show:
- Erectile dysfunction: 1-2% of patients (vs 0.7% in placebo group)
- Decreased libido: 1-1.5%
- Ejaculatory disorders: 1.2%
Most effects are reversible upon discontinuation. The nocebo effect is well-documented in the scientific literature.
Optimal Protocol
- Finasteride: 1mg/day, oral, at a fixed time
- Dutasteride: 0.5mg/day OR 0.5mg/week depending on profile and tolerance
- Evaluate efficacy at 12 months minimum
- Stopping = progressive relapse within 6-12 months: lifelong treatment
- Annual monitoring recommended (PSA, hormonal panel if needed)
FUE Transplant + DHT Inhibitors: The Complete Strategy
- Finasteride/Dutasteride for miniaturizing zones: stabilizes what remains
- FUE transplant for definitively extinct zones: restores what is lost
Starting an inhibitor before the transplant often stabilizes progression and optimizes surgical planning.
Finasteride, dutasteride, or FUE transplant — which solution is right for your hair loss? Free consultation at Phoenix Hair Center Paris — personalized diagnosis, no commitment.
