Dutasteride
C
Dutasteride
Dutasteride
Oral
Dutasteride is a dual type I + type II 5α-reductase inhibitor that reduces serum DHT by approximately 90-95%, more potently than finasteride [1] . Used as adjunctive therapy in transfeminine HRT when finasteride proves insufficient.
Mechanism
Section titled “Mechanism”Dutasteride simultaneously inhibits both type I and type II 5α-reductase:
- Type I: Primarily found in skin (sebaceous glands) and liver
- Type II: Primarily found in hair follicles and prostate
This dual inhibition achieves 90-95% DHT reduction, compared to ~65-70% with finasteride.
Comparison with Finasteride
Section titled “Comparison with Finasteride”| Feature | Dutasteride | Finasteride |
|---|---|---|
| Target | Type I + II | Type II only |
| DHT reduction | ~90-95% | ~65-70% |
| Half-life | ~4-5 weeks | ~6-8 hours |
| Onset | 3-6 months | 3-6 months |
| Washout after stopping | Months (very long half-life) | Weeks |
| Generic availability | Limited | Widespread |
| Evidence level | C | B |
Dosing
Section titled “Dosing”| Indication | Dose | Notes |
|---|---|---|
| Adjunct to HRT | 0.5 mg/day | Standard dose; do not exceed |
- 0.5 mg/day is the only recommended dose
- Due to the very long half-life (~4-5 weeks), missing one day does not require make-up dosing
- Capsules must not be opened or chewed
Brands & Availability
Section titled “Brands & Availability”| Brand | Strength | Notes |
|---|---|---|
| Avodart | 0.5 mg capsule | Original brand |
| Generics | 0.5 mg capsule | Available in some regions |
Monitoring
Section titled “Monitoring”- T: Continue routine HRT monitoring every 3 months
- DHT (optional): Can confirm 5αRI effect
- PSA: Dutasteride lowers PSA; inform your doctor if being tested
Contraindications
Section titled “Contraindications”- Dutasteride allergy
- Severe hepatic impairment (dutasteride is metabolized via CYP3A4)
- Concomitant strong CYP3A4 inhibitors (e.g. ketoconazole) — may cause dutasteride accumulation