Finasteride works by decreasing the conversion of testosterone to DHT, a more potent form of testosterone. DHT plays a central role in androgenetic alopecia (or baldness) by decreasing hair growth and causing follicle death.
Although it is a generally well-tolerated and safe medication, it frequently causes sexual side effects, such as decreased libido, erectile dysfunction, difficulty achieving orgasm and ejaculation disorders. The incidence of these side effects varies from about 2 to 19% in studies, but reached as high as 90% in a study based on standardized interviews published in 2011. Typically, these effects are not permanent and dissipate after treatment is stopped. In contrast, in the same study, sexual side effects persisted on average 3 years after discontinuation, and 20% of patients still had these effects more than 6 years after discontinuation. However, this analysis cannot determine the true incidence of persistent sexual side effects because of its many limitations. Additional studies are needed to validate these results. Other less common side effects include drops in blood pressure, dizziness and gynecomastia.
In addition, the efficacy of finasteride for hair regrowth is modest. In studies, the first benefits appeared after 3 months of treatment. After 6 to 12 months, average hair growth was 9% higher with finasteride compared to placebo and this difference continued to increase over time. After 4 years, hair growth was 24% higher than placebo. In addition, 67% of patients achieved a clinically meaningful response after 2 years of treatment.
When making a decision, it is important to weigh the risks and benefits of the treatment, because as with any medication, there is a risk of adverse effects. Do the benefits of the drug outweigh the risks? Is the modest effectiveness of finasteride worth the risk of sexual side effects? These are all questions that should be discussed with your doctor and pharmacist.
Before turning to finasteride, better-tolerated alternatives can be tried, such as topical minoxidil application, low-level laser therapy (LLLT), platelet-rich plasma (PRP) therapies and hair transplantation.
I hope my answer sheds some light on the subject,
Raphaël Parent, Pharmacist