Finasteride Vs Dutasteride
there is evidence that dutasteride is three times as potent as finasteride at inhibiting type II 5-alpha reductase and more than 100 times as potent at inhibiting the type I enzyme. This suggests enhanced efficacy over the existing finasteride.
Because of these increased effects on the 5-alpha reductase enzymes, scalp and serum levels of DHT are more affected. Dutasteride can decrease serum DHT by more than 90%, while finasteride decreases serum DHT by 70%. One 4-year study of men on dutasteride 0.5 mg continuously for BPH showed a near complete suppression of serum DHT, decreasing by a mean of 93% from baseline. In comparison with dutasteride, finasteride reportedly reduces scalp DHT by only 34% to 41%.
As with finasteride, inhibition of the 5-alpha reductase enzyme can increase levels of testosterone locally in the scalp. However, the increased efficacy means that it can also increase testosterone levels in the serum. The 4-year study above noted that serum testosterone rose by 25% from 3951.9 pg/mL to 4767.0 pg/mL. Minimal dose-dependent effects on serum testosterone have been described for finasteride.