5α-reductase inhibitors (hair loss)5α-reductase inhibitorA compound that inhibits the 5α-reductase enzyme, reducing conversion of testosterone into dihydrotestosterone (DHT).
Finasteride vs Dutasteride
The table compares the compounds’ key data from their entry pages. Open each compound’s full entry for details. Educational content, not medical advice.
 Finasteride |  Dutasteride | |
|---|---|---|
| What it is | Selective inhibitor of type II 5-alpha-reductase. FDA-approved for androgenetic alopecia (Propecia 1 mg) and BPH (Proscar 5 mg). Reduces DHT formation by ~70%. | Dual 5-alpha-reductase inhibitor (type I + II). FDA-approved for BPH (Avodart 0.5 mg), off-label for androgenetic alopecia (approved in South Korea/Japan). Reduces serum DHT by ~90-95%, more strongly than finasteride. |
| ATC codeATC codeThe WHO Anatomical Therapeutic Chemical code that classifies drugs by organ system and mechanism. | D11AX10 (1mg) / G04CB01 (5mg) | G04CB02 |
| Prescription status | Prescription only (Rx) | Prescription (Rx); off-label for AGA |
| Mechanism of actionMechanism of actionThe molecular pathway by which a compound acts in the body (e.g. which receptor or enzyme it binds). | Selective inhibition of type II 5-alpha-reductase, ~70% DHT reduction | Dual 5-alpha-reductase (I + II) inhibition, ~90-95% DHT reduction |
| Half-lifeHalf-lifeThe time for the compound’s plasma concentration to fall by half; indicates how fast it clears and how often it is dosed. | 5-6 hours plasma, 96+ hours enzyme affinity | ~5 weeks (terminal) – far longer than finasteride |
| Onset of actionOnsetThe time from dosing until a measurable effect appears. | 3-6 months (hair stabilization), 6-12 months (regrowth) | 3-6 months (hair stabilization), 6-12 months (regrowth) |
| Full entry | Open → | Open → |
What it is
FinasterideSelective inhibitor of type II 5-alpha-reductase. FDA-approved for androgenetic alopecia (Propecia 1 mg) and BPH (Proscar 5 mg). Reduces DHT formation by ~70%.
DutasterideDual 5-alpha-reductase inhibitor (type I + II). FDA-approved for BPH (Avodart 0.5 mg), off-label for androgenetic alopecia (approved in South Korea/Japan). Reduces serum DHT by ~90-95%, more strongly than finasteride.
ATC codeATC codeThe WHO Anatomical Therapeutic Chemical code that classifies drugs by organ system and mechanism.
FinasterideD11AX10 (1mg) / G04CB01 (5mg)
DutasterideG04CB02
Prescription status
FinasteridePrescription only (Rx)
DutasteridePrescription (Rx); off-label for AGA
Mechanism of actionMechanism of actionThe molecular pathway by which a compound acts in the body (e.g. which receptor or enzyme it binds).
FinasterideSelective inhibition of type II 5-alpha-reductase, ~70% DHT reduction
DutasterideDual 5-alpha-reductase (I + II) inhibition, ~90-95% DHT reduction
Half-lifeHalf-lifeThe time for the compound’s plasma concentration to fall by half; indicates how fast it clears and how often it is dosed.
Finasteride5-6 hours plasma, 96+ hours enzyme affinity
Dutasteride~5 weeks (terminal) – far longer than finasteride
Onset of actionOnsetThe time from dosing until a measurable effect appears.
Finasteride3-6 months (hair stabilization), 6-12 months (regrowth)
Dutasteride3-6 months (hair stabilization), 6-12 months (regrowth)
Full entry