The oral hair loss treatment drug Propecia™, aka 1 mg finasteride, preferentially inhibits the type 2 isoform of the enzyme 5-alpha Reductase. This enzyme, which converts the androgen hormone testosterone (T) into its more pathologic metabolite 5-alpha dihydrotestosterone (DHT) can be thought of as the match that lights the fuse in precipitating several disease phenotypes, including pattern hair loss and benign prostatic hyperplasia (BPH). While type 1 5AR is predominant in liver, type 2 is predominant in prostate, seminal vesicles, epididymis & hair follicles.
Originally developed as a therapy against BPH, 5 mg finasteride known as Proscar™ was reformulated in 1 mg strength and rebranded Propecia™. The mechanism of action of finasteride is based on its preferential blockade of Type 2 5AR through the formation of a stable complex with the enzyme. Inhibition of Type 2 5AR blocks the peripheral conversion of testosterone to DHT, resulting in significant decreases in serum and tissue DHT concentrations. While clinical research suggests that Propecia™ can reduce hair loss, unfortunately, Propecia™ has been linked to serious negative side effects. Reported side effects of Propecia™ include impotence, loss of interest in sex, trouble having an orgasm, abnormal ejaculation, gynecomastia (male breast enlargement), depression, & suicidal ideation. Due to its potential for causing feminizing birth defects, Propecia™ is not indicated for use by women.
Interestingly, while also demonstrating efficacy in a number of clinical trials, including placebo-controlled, double blind research (e.g. https://www.ncbi.nlm.nih.gov/pubmed/12006122) HairGenesis® has never been linked to negative side effects observed with Propecia™. Moreover, HairGenesis® was recently shown to dramatically outperform Propecia™ in a series of University of Chicago based studies: https://www.ncbi.nlm.nih.gov/pubmed/26990224
Finally, while Propecia™ operates as a monotherapy, HairGenesis® has been demonstrated to work thru a multi-faceted series of mechanisms, thereby targeting more than one causative pathway linked to pattern hair loss (https://www.ncbi.nlm.nih.gov/pubmed/19692448). This is highly relevant as common pattern hair loss has been definitively proven to be a complex trait disorder – meaning that there are multiple genetic, epigenetic and environmental factors operative in the onset and progression of the hair loss disease phenotype. Therefore, by targeting multiple triggers, HairGenesis® can arguably be said to be operating far more efficiently and effectively. Most importantly, HairGenesis®, in its maximal dosage, has also been show to be extremely safe for women as well as men.