Which to choose?
Finasteride: first choice for androgenetic alopecia (the licensed indication) and standard BPH. Dutasteride: high-volume BPH, or when finasteride is not effective. Both are prescription only. NEVER take either if the partner could be pregnant (fetal risk).
Point-by-point comparison
Brands: Proscar · Propecia
Brands: Avodart
| Finasteride | Dutasteride | |
|---|---|---|
| Mechanism | Selectively inhibits type 2 5-alpha-reductase, reducing conversion of testosterone to DHT. | Inhibits both isoenzymes (types 1 and 2), reducing DHT by around 95%. |
| Indications | Benign prostatic hyperplasia (5 mg, Proscar). Male androgenetic alopecia (1 mg, Propecia). | BPH. Off-label use in androgenetic alopecia. |
| Adult dose | BPH: 5 mg/day. Hair loss: 1 mg/day. | 0.5 mg/day. |
| Onset of effect | Urinary symptoms improve at 3-6 months. Hair loss: 3-6 months to stabilise shedding. | Urinary symptoms improve at 3-6 months. |
| Duration of effect | While treatment continues. Reversible within weeks of stopping. | Much longer half-life (5 weeks) — prolonged residual effect. |
| Pregnancy | CONTRAINDICATED in women of childbearing potential (male fetal genital teratogenicity). | CONTRAINDICATED. |
| Breastfeeding | CONTRAINDICATED. | CONTRAINDICATED. |
| Paediatric use | Not indicated. | Not indicated. |
| Advantages | More studied and more widely used. Sexual adverse effects somewhat less frequent. | Greater DHT suppression (95%). Better in high-volume BPH. |
| Disadvantages | Inhibits only the type 2 isoenzyme. DHT reduction around 70%. | Very long half-life. Sexual adverse effects potentially greater. Not licensed for hair loss. |
Source: BNF, EAU guidelines, Spanish SmPC (AEMPS)
Frequently asked questions
Which is better, finasteride or dutasteride?
Finasteride: first choice for androgenetic alopecia (the licensed indication) and standard BPH. Dutasteride: high-volume BPH, or when finasteride is not effective. Both are prescription only. NEVER take either if the partner could be pregnant (fetal risk).
Can finasteride or dutasteride be taken in pregnancy?
Finasteride: CONTRAINDICATED in women of childbearing potential (male fetal genital teratogenicity). Dutasteride: CONTRAINDICATED. Always ask a doctor or pharmacist before taking a medicine in pregnancy.
And while breastfeeding?
Finasteride: CONTRAINDICATED. Dutasteride: CONTRAINDICATED.