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Hair color or style is one of the first things we notice about another person. Your hair is a part of your identity, so losing your hair can feel like a blow to your sense of self, and you might be eager to fix this issue quickly. Unfortunately, there are many gimmicks on the market, so how do you know what really works?
In this article, we’ll look at one of the most popular hair loss treatments on the market, finasteride, to see if it works, what people use it for, and what side effects you should be aware of before taking it.
Does finasteride work?
It does! Finasteride is not one of those “snake oil” options on the market.
Finasteride is an oral medication in a class of drugs called 5-alpha-reductase inhibitors, often known by its brand name, Propecia. It’s very effective at preventing further hair loss in patients with androgenetic alopecia (AGA, often called male pattern hair loss) (Kaufman, 2008). It also promotes hair regrowth to reverse at least some hair loss for many balding patients (Adil, 2017).
It’s more effective in men than in women, though, and is only FDA-approved for male patients with AGA (Varothai, 2014). Yes, women can get androgenetic alopecia, too. It affects up to 38% of women over 70, but other medications are more effective for AGA in women (Phillips, 2017).
In androgenetic alopecia, excess dihydrotestosterone (DHT) attacks the hair follicles on the head, causing miniaturization of the hair follicles and, eventually, hair loss. Finasteride works by preventing the conversion of testosterone into DHT.
That same mechanism makes finasteride effective at treating benign prostatic hyperplasia (BPH), too. In BPH, the prostate gets enlarged, and finasteride helps shrink the prostate’s size by decreasing DHT levels (Smith, 2009).
What is finasteride used for?
Although we often think of finasteride as a hair loss drug, it was a treatment for BPH first (Zito, 2020). Today, it’s used just as commonly to treat hair loss as it is for BPH. Let’s look more closely at how finasteride helps with both of these conditions.
Hair loss can happen for a whole host of reasons, including genetic, hormonal, autoimmune, and nutrition-related causes, among others. Androgenetic alopecia (AGA) is the most common cause of hair loss, occurring in up to 50% of men over 50 and up to 38% of women over 70 (Phillips, 2017). AGA happens when the body has a hyper response to androgens (male sex hormones), one of which is DHT.
Finasteride treats hair loss by lowering how much testosterone converts into DHT, thereby decreasing the body’s levels of DHT. One study showed finasteride was 93% more effective than placebo at preventing further hair loss (Kaufman, 2008). Another study showed improvement in new hair growth in 48% of participants in the first year and 66% in the second year (McClellan, 1999).
While finasteride works on its own, it’s even more effective at treating hair loss when combined with minoxidil (brand name Rogaine), an over-the-counter topical treatment that goes directly on the scalp (Chen, 2020).
Finasteride has been an approved treatment for BPH since 1992, but what is BPH, and how does finasteride help?
BPH is a condition in which the prostate is enlarged, most commonly in men over the age of 50. This often causes difficulty with urination.
Finasteride is a 5-alpha reductase inhibitor that lowers DHT levels in the blood and prostate by preventing testosterone from converting into DHT. When levels of DHT in the prostate are lowered, the size of the prostate can be reduced, too, in some cases by up to 19% (Smith, 2009).
The dose of finasteride is higher for treating BPH than it is for treating hair loss. The higher dose version is sold under the brand name Proscar.
Finasteride is only FDA-approved for hair loss and BPH, though it is sometimes used off-label in women with hirsutism (unwanted hair growth caused by high levels of androgen hormones).
Because finasteride lowers androgen hormones such as DHT, there was some hope it might also be useful in combination with estrogen therapy in transgender women, but we don’t have enough research yet showing that it works for that purpose. As of now, hair loss and BPH are the only approved medical conditions for finasteride.
Side effects of finasteride
Finasteride might be sounding pretty good right about now—and it is! It’s effective for many patients to stop hair loss in its tracks and increase hair count, and for patients with BPH, it relieves symptoms by decreasing the size of the prostate.
Like most good things in life, though, finasteride can come with some bad, too.
The side effects patients tend to be most worried about with finasteride are sexual side effects, including erectile dysfunction, low libido, and premature ejaculation. Many patients are so distressed about these potential side effects that they decide to forego treatment, which is understandable.
There’s good news and bad news. First, the good news: Clinical trials showed sexual dysfunction from finasteride is unlikely to happen when it’s used to treat hair loss since the dose is quite low (McClellan, 1999). The not-so-good news is that patients taking finasteride for BPH are at an increased risk of developing sexual side effects, particularly erectile dysfunction (Fertig, 2017). This is likely because of the much higher doses needed to treat BPH.
Other serious side effects of finasteride are unlikely but possible. These include:
- Breast enlargement (called gynecomastia). In very rare cases, male breast cancer can happen, too, so let your healthcare provider know if you are experiencing any pain, lumps, or discharge from your nipples.
- Depression and suicidal thoughts
- Male infertility
- Allergic reactions, such as rash or itching
These are just a few of the possible side effects, so be sure to speak with your healthcare provider if you notice any other persistent changes while on this medication (“Finasteride,” n.d.). You can learn more about finasteride side effects here.
Talk to your healthcare provider
While finasteride is effective and well-tolerated by most patients for both hair loss and BPH, it’s important to speak with your healthcare provider about any concerns you may have. Your complete medical history will help your healthcare provider make informed decisions about whether finasteride is right for you and which dosage is most appropriate.
- Adil, A., & Godwin, M. (2017). The effectiveness of treatments for androgenetic alopecia: A systematic review and meta-analysis. Journal of the American Academy of Dermatology, 77(1), 136–141.e5. doi: 10.1016/j.jaad.2017.02.054. https://pubmed.ncbi.nlm.nih.gov/28396101/
- Chen, L., Zhang, J., Wang, L., Wang, H., & Chen, B. (2020). The Efficacy and Safety of Finasteride Combined with Topical Minoxidil for Androgenetic Alopecia: A Systematic Review and Meta-analysis. Aesthetic plastic surgery, 44(3), 962–970. doi: 10.1007/s00266-020-01621-5. https://pubmed.ncbi.nlm.nih.gov/32166351/
- Fertig, R. M., Gamret, A. C., Darwin, E., & Gaudi, S. (2017). Sexual side effects of 5-α-reductase inhibitors finasteride and dutasteride: A comprehensive review. Dermatology Online Journal, 23(11). Retrieved from https://escholarship.org/uc/item/24k8q743
- Finasteride — drug summary. Prescribers’ Digital Reference. https://www.pdr.net/drug-summary/Propecia-finasteride-378.609. Accessed December 9, 2020.
- Kaufman, K. D., Rotonda, J., Shah, A., & Meehan, A. G. (2008). Long-term treatment with finasteride 1 mg decreases the likelihood of developing further visible hair loss in men with androgenetic alopecia (male pattern hair loss). European Journal of Dermatology, 18(4), 400–406. doi: 10.1684/ejd.2008.0436. https://pubmed.ncbi.nlm.nih.gov/18573712/
- Mcclellan, K. J., & Markham, A. (1999). Finasteride: a review of its use in male pattern hair loss. Drugs, 57(1), 111–126. doi: 10.2165/00003495-199957010-00014, https://www.ncbi.nlm.nih.gov/pubmed/9951956
- Phillips, T. G., Slomiany, W. P., & Allison, R. (2017). Hair Loss: Common Causes and Treatment. American Family Physician, 96(6), 371–378. https://pubmed.ncbi.nlm.nih.gov/28925637/
- Smith, A. B., & Carson, C. C. (2009). Finasteride in the treatment of patients with benign prostatic hyperplasia: a review. Therapeutics and clinical risk management, 5(3), 535–545. doi: 10.2147/tcrm.s6195. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2710385/
- Varothai, S., & Bergfeld, W. F. (2014). Androgenetic alopecia: an evidence-based treatment update. American Journal of Clinical Dermatology, 15(3), 217–230. doi: 10.1007/s40257-014-0077-5. https://pubmed.ncbi.nlm.nih.gov/24848508/
- Zito PM, Bistas KG, Syed K (2020). Finasteride. StatPearls. Available from: https://www.ncbi.nlm.nih.gov/books/NBK513329/
Dr. Mike is a licensed physician and the Director, Medical Content & Education at Ro.