It depends upon dosage. Neither is necessarily better than the other in the abstract as dutasteride might wipe out more of the first type of reductase than is necessary for many people. How much depends on dosage but in general, duta wipes out all of type one, over 90 percent and 70 percent of type II if I recall correctly. finasteride reduces only type I by about 70 percent at standard dosaging. Since these are titrated often, it's difficult to be more precise but generally titrating upwards from 1 mg of finasteride to 5 mg before trying duta is less likely to cause sheds possibly. There's actually three types of reductases although the third seems to be less discussed and perhaps less implicated in hair loss. The nomenclature appears to be inconsistent related to which type of reductase is referred to as Type I.
Except for eradication possibly of certain neurotransmitters, Duta is better for hair growth and improvement but might cause more shedding.
en.wikipedia.org
Dutasteride belongs to a class of drugs called
5α-reductase inhibitors, which block the action of the
5α-reductase enzymes that convert testosterone into DHT.
[42] It
inhibits all three
forms of
5α-reductase, and can decrease DHT levels in the blood by up to 98%.
[1][43][44] Specifically it is a
competitive,
mechanism-based (
irreversible)
inhibitor of all three
isoforms of 5α-reductase,
types I,
II, and
III (
IC50 values are 3.9 nM for type I and 1.8 nM for type II).
[1][43][45][46] This is in contrast to finasteride, which is similarly an irreversible inhibitor of 5α-reductase
[46][47] but only inhibits the type II and III
isoenzymes.
[43] As a result of this difference, dutasteride is able to achieve a reduction in circulating DHT levels of up to 98%, whereas finasteride is able to achieve a reduction of only 65 to 70%.
[44][2][42][48] In spite of the differential reduction in circulating DHT levels, the two drugs decrease levels of DHT to a similar extent of approximately 85 to 90% in the
prostate gland,
[48] where the type II isoform of 5α-reductase predominates.
[45]
The 2 5α-reductase inhibitors (5ARIs), dutasteride and finasteride, suppress dihydrotestosterone (DHT) by inhibiting the conversion of testosterone to DHT. Finasteride inhibits only the Type 2 5AR isoenzyme, whereas dutasteride, the only dual 5ARI, selectively inhibits both Type 1 and Type 2 5AR isoenzymes.
