Dutasteride 0.5 mg is the only commercially available strength and is the standard dose for both FDA-approved BPH treatment and off-label hair loss use. At 0.5 mg daily, median serum DHT falls by about 85% after one week and about 90% after two weeks, reaching about 94% after a year of treatment.
Why 0.5 mg?
The 0.5 mg dose came out of Phase II dose-ranging work and was carried into the three pivotal Phase III BPH trials. Higher doses have been studied (the Olsen hair-loss trial included a 2.5 mg arm, and 5 mg daily was studied in men awaiting prostate surgery), but 0.5 mg is the only strength the FDA has approved and the only one marketed.
What the Capsule Contains
Dutasteride 0.5 mg soft gelatin capsules contain the drug dissolved in a mixture of mono-di-glycerides of caprylic/capric acid and butylated hydroxytoluene (BHT). The inactive excipients in the capsule shell are ferric oxide (yellow), gelatin, glycerin and titanium dioxide. The capsules are oblong, opaque and dull yellow, printed with “GX CE2” in red edible ink on one side.
Pharmacokinetics at 0.5 mg
| Parameter | Value |
|---|---|
| Time to peak serum concentration (Tmax) | 2 to 3 hours post-dose |
| Average steady-state serum concentration | 40 ng/mL after 1 year at 0.5 mg/day |
| Absolute bioavailability | ~60% (range 40% to 94%) |
| Median serum DHT reduction | 90% at 2 weeks, 94% at 1 year |
| Terminal elimination half-life | ~5 weeks at steady state |
All dosing options · Dosing for hair loss · Twice-weekly dosing
⚠️ Contraindicated in Pregnancy: Dutasteride is contraindicated in women who are or may become pregnant. Exposure to even crushed or leaking capsules through skin contact can harm a male fetus. Women must not handle broken dutasteride capsules. Due to the ~5-week half-life, the drug persists in the body for months after stopping.
Sources
- FDA. Avodart prescribing information. accessdata.fda.gov