5α-reductase inhibitors5α-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 (Propecia / Proscar) | Dutasteride (Avodart) | |
|---|---|---|
| What it is | Selective type-II 5α-reductase inhibitor. FDA-approved (Proscar 1992 BPH 5 mg, Propecia 1997 AGA 1 mg). In AAS: scalp DHT suppression to slow hair loss in genetically predisposed users. Type-I 5AR not inhibited. | Dual 5α-reductase inhibitor (type-I + type-II). FDA-approved (2001 GSK) for BPH. In AAS: ~90% scalp DHT + acne reduction. Long t1/2 ~5 weeks – washout ~6 months. Higher PFS risk vs finasteride. |
| MechanismMechanism of actionThe molecular pathway by which a compound acts in the body (e.g. which receptor or enzyme it binds). | Selective type-II 5α-reductase inhibitor, ~70% scalp DHT suppression at 1 mg/day | Dual 5α-reductase inhibitor (type-I + type-II), ~90% scalp DHT suppression at 0.5 mg/day |
| Dosing (AAS hair-loss prevention)Hair-loss treatmentA category of compounds used to treat androgen-related hair loss (androgenetic alopecia) by different mechanisms (e.g. reducing DHT or increasing follicle perfusion). | 1 mg/day (Propecia) continuous during cycle | — |
| 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. | ~6 h parent, pharmacodynamic effect 24+ h enzyme inhibition | ~5 weeks (very long, steady-state ~6 months, washout ~6 months) |
| OnsetOnsetThe time from dosing until a measurable effect appears. | DHT reduction measurable 24 h, hair stabilization 3-6 months | DHT reduction measurable 1 week, hair stabilization 3-6 months |
| Legal statusLegal / WADA statusThe compound’s regulatory status (e.g. prescription) and its place on the WADA prohibited-in-sport list. | FDA + EMA Rx, HU + PL approved, WADA allowed (not 5AR-banned) | FDA + EMA Rx (BPH), HU + PL approved, off-label AGA US/EU, WADA allowed |
| Dosing (AAS hair-loss + acne)Hair-loss treatmentA category of compounds used to treat androgen-related hair loss (androgenetic alopecia) by different mechanisms (e.g. reducing DHT or increasing follicle perfusion). | — | 0.5 mg/day continuous or every other day (cost-saving) |
| Full entry | Open → | Open → |
What it is
Finasteride (Propecia / Proscar)Selective type-II 5α-reductase inhibitor. FDA-approved (Proscar 1992 BPH 5 mg, Propecia 1997 AGA 1 mg). In AAS: scalp DHT suppression to slow hair loss in genetically predisposed users. Type-I 5AR not inhibited.
Dutasteride (Avodart)Dual 5α-reductase inhibitor (type-I + type-II). FDA-approved (2001 GSK) for BPH. In AAS: ~90% scalp DHT + acne reduction. Long t1/2 ~5 weeks – washout ~6 months. Higher PFS risk vs finasteride.
MechanismMechanism of actionThe molecular pathway by which a compound acts in the body (e.g. which receptor or enzyme it binds).
Finasteride (Propecia / Proscar)Selective type-II 5α-reductase inhibitor, ~70% scalp DHT suppression at 1 mg/day
Dutasteride (Avodart)Dual 5α-reductase inhibitor (type-I + type-II), ~90% scalp DHT suppression at 0.5 mg/day
Dosing (AAS hair-loss prevention)Hair-loss treatmentA category of compounds used to treat androgen-related hair loss (androgenetic alopecia) by different mechanisms (e.g. reducing DHT or increasing follicle perfusion).
Finasteride (Propecia / Proscar)1 mg/day (Propecia) continuous during cycle
Dutasteride (Avodart)—
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.
Finasteride (Propecia / Proscar)~6 h parent, pharmacodynamic effect 24+ h enzyme inhibition
Dutasteride (Avodart)~5 weeks (very long, steady-state ~6 months, washout ~6 months)
OnsetOnsetThe time from dosing until a measurable effect appears.
Finasteride (Propecia / Proscar)DHT reduction measurable 24 h, hair stabilization 3-6 months
Dutasteride (Avodart)DHT reduction measurable 1 week, hair stabilization 3-6 months
Legal statusLegal / WADA statusThe compound’s regulatory status (e.g. prescription) and its place on the WADA prohibited-in-sport list.
Finasteride (Propecia / Proscar)FDA + EMA Rx, HU + PL approved, WADA allowed (not 5AR-banned)
Dutasteride (Avodart)FDA + EMA Rx (BPH), HU + PL approved, off-label AGA US/EU, WADA allowed
Dosing (AAS hair-loss + acne)Hair-loss treatmentA category of compounds used to treat androgen-related hair loss (androgenetic alopecia) by different mechanisms (e.g. reducing DHT or increasing follicle perfusion).
Finasteride (Propecia / Proscar)—
Dutasteride (Avodart)0.5 mg/day continuous or every other day (cost-saving)