Comparison of oral minoxidil, finasteride, and dutasteride for treating androgenetic alopecia.

Background: Androgenetic alopecia (AGA) is the most common cause of hair loss, often challenging to treat. While oral finasteride (1 mg/d) is an FDA-approved treatment for male AGA, oral minoxidil and oral dutasteride are not approved yet. However, clinicians have been increasingly using these two drugs off-label for hair loss. Recently, Japan and South Korea have approved oral dutasteride (0.5 mg/d) for male AGA.

Efficacy and safety: A probable efficacy ranking, in decreasing order, is - dutasteride 0.5 mg/d, finasteride 5 mg/d, minoxidil 5 mg/d, finasteride 1 mg/d, followed by minoxidil 0.25 mg/d. Oral minoxidil predominantly causes hypertrichosis and cardiovascular system (CVS) symptoms/signs in a dose-dependent manner, whereas oral finasteride and dutasteride are associated with sexual dysfunction and neuropsychiatric side effects.

Pharmacokinetics and pharmacodynamics: The average plasma half-lives of minoxidil, finasteride, and dutasteride are ∼4 h, ∼4.5 h, and ∼5 weeks, respectively. Minoxidil acts through multiple pathways to promote hair growth. It has been shown as a vasodilator, an anti-inflammatory agent, a Wnt/β-catenin signaling inducer, and an antiandrogen. Finasteride inhibits 5α-reductase (5AR) type II isoenzyme, while dutasteride inhibits both type I and type II. Thus, dutasteride suppresses DHT levels more than finasteride in the serum and scalp.