Dutasteride vs Finasteride Study
Olsen E. et. al.
In the study, 416 men with male pattern hair loss (MPHL) ages 21 to 45 years old, were randomized to receive dutasteride 0.05, 0.1, 0.5 or 2.5 mg, finasteride 5 mg, or placebo daily for 24 weeks. The results of the study showed that dutasteride increased hair counts in a dose-dependent fashion and dutasteride 2.5 mg was superior to finasteride 5mg at 12 and 24 weeks.
Although testosterone is the major circulating androgen, to be maximally active in scalp hair follicles it must first be converted to dihydrotestosterone (DHT) by the enzyme 5?-reductase. The importance of DHT as a causative factor in male pattern hair loss is shown by the absence of this MPHL in men with a congenital deficiency of the type 2 5?-reductase enzyme. A type 1 5?-reductase, which also metabolizes testosterone to DHT, differs in its location and amount in different tissues. In the skin, type 1 5?-reductase is the principal isoenzyme in sebaceous and sweat glands. There is no recognized genetic deficiency of type 1 5?-reductase in humans to assess its role in MPHL.
Dutasteride (Avodart) inhibits both type 1 and type 2 5?-reductase and is approved at the 0.5-mg dose for treatment of symptomatic benign prostatic hyperplasia (BPH). It is about 3 times as potent as finasteride at inhibiting type 2 5?-reductase and more than 100 times as potent at inhibiting the type 1 5?-reductase enzyme.
Dutasteride caused scalp and serum dihydrotestosterone levels to decrease and testosterone levels to increase in a dose-dependent fashion. Whereas 5-mg finasteride decreases serum DHT by about 70%, dutasteride can decrease serum DHT by more than 90%.
Results
In this phase II, dose-ranging study, 2.5-mg dutasteride was superior to 5-mg finasteride in improving scalp hair growth in men between ages 21 and 45 years with MPHL as judged by target area hair counts, expert panel assessment, and investigator assessment at 12 and 24 weeks.
In a test area at 24 weeks, results showed:
Placebo -32.3 hairs
Finasteride 5mg 75.6 hairs
Dutasteride 0.1 mg 78.5 hairs
Dutasteride 0.5 mg 94.6 hairs
Dutasteride 2.5 mg 109.6 hairs
Dutasteride 2.5mg vs. 0.5mg
The 2.5-mg dutasteride dose was consistently superior to 0.5-mg dutasteride in promoting scalp hair growth. The 2.5-mg dose was also better than the 0.5-mg dose at suppressing scalp DHT (79% vs. 51%), whereas it was only marginally better at suppressing serum DHT (96% vs. 92%). This difference in the dose-response of serum and scalp DHT to inhibition with dutasteride is likely to be due to the greater contribution of type 1 5?-reductase to scalp DHT concentrations. |
