Dutasteride vs. finasteride: is one better for hair loss?

Swollen glands. Achy muscles. A sensitive stomach. We've all been there, definitely feeling not our best but not sick enough to use that sick day or skip that workout. And, let's face it, we generally regret it when we have to take double the time off. It's about time to call these things as soon as they pop up, especially if you've noticed your hair thinning lately. While stress, vitamin deficiencies, and a lack of protein can all cause hair loss, they're rare conditions. You're likely looking at inherited baldness or androgenic alopecia (also called androgenetic alopecia), which causes 95% of cases of hair loss in men. Once a hair follicle is "dead," it's difficult to revive, which is why getting treatment—like using dutasteride or finasteride—early is critical.

Androgenic alopecia affects both men and women and generally causes gradual hair loss, eventually leading to male pattern baldness (MPB) and female pattern baldness. Up to 50% of men aged 50 years old have androgenic alopecia, and the prevalence of male pattern baldness increases with age (Phillips, 2017). That's because this particular type of hair loss has to do with your hormones, which change as you get older.

MPB, or androgenic alopecia, is caused by dihydrotestosterone (DHT)—a derivative of testosterone. DHT causes hair follicles to shrink and lose the ability to create long, thick, pigmented hairs in a process called "miniaturization." Testosterone is converted into DHT by an enzyme called 5-alpha reductase. This enzyme comes in different forms, but one of them is responsible for converting testosterone to DHT on the scalp. Medicines such as dutasteride and finasteride, though they may be different, work the same way; both stop the conversion of testosterone to DHT by blocking 5-alpha reductase.

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While finasteride (the generic form of Propecia) and dutasteride (commonly sold under the brand name Avodart) are both 5 alpha-reductase inhibitors, there's one big difference between the two: The U.S. Food and Drug Administration (FDA) has approved finasteride for the treatment of hair loss and dutasteride for the treatment of benign prostatic hyperplasia (BPH), also known as prostate enlargement or an enlarged prostate. Dutasteride may be used off-label to treat male pattern baldness or hair loss.

Like we mentioned earlier, timing may be key here. Finasteride works most effectively if it is started earlier in the hair loss process. Though the specific point in time differs from person to person, permanent scalp changes happen during the balding process that prevent hair regrowth. If finasteride is taken at this point, it may still be effective at preventing further hair loss. In fact, this medication prevented further hair loss in 83% of men who took it for two years, and 66% of men had some hair regrowth, research has found. In the short-term, hair counts increased in the first year compared to those of men in the placebo group, and the five-year follow-up showed enduring improvements in scalp hair. By five years, men treated with finasteride were also far more satisfied with their hairlines (Shapiro, 2003).

There are two types, called isoenzymes, of 5-alpha reductase: type 1 and type 2. Finasteride specifically blocks type 2. Dutasteride blocks both type 1 and type 2 5-alpha reductase, which means it prevents more testosterone from being converted into DHT.

Researchers have even compared the treatments, no pun intended, head-to-head. Clinical trials have shown that dutasteride treatment lowers serum DHT levels more than finasteride, but this doesn't necessarily translate to hair loss (Nickel, 2004). But a meta-analysis of studies that looked specifically at both medications' effects on hair found that dutasteride was more effective at treating androgenetic alopecia than finasteride. Total hair counts were higher in the group treated with dutasteride, as was subject assessment of the results of 24 weeks of treatment (Zhou, 2019).

This likely won't be your deciding factor when choosing between finasteride and dutasteride, but the meta-analysis that found dutasteride more effective at treating male pattern baldness also found that the side effects were similar across both medications (Zhou, 2019). Both, however, are generally well tolerated. Common sexual side effects include decreased sex drive, trouble getting or keeping an erection (erectile dysfunction), and a decrease in semen. More adverse effects have been reported, however. These include breast tenderness and enlargement, depression, allergic reactions, and problems with ejaculation.

You should also tell your healthcare provider that you're taking finasteride or dutasteride if you're getting screened for prostate cancer. These medications can affect a blood test called PSA (prostate-specific antigen), which is used as a screening test for prostate cancer.

Studies have found that dutasteride is more effective at treating male pattern baldness. This medication is not only shown to be potentially more effective at treating hair loss but also shows the same rate and types of side effects as finasteride. That means you likely won't be trading efficacy for more side effects. If for some reason, you cannot use dutasteride, finasteride may be an option—especially if you're in the beginning stages of hair loss since it shows its greatest efficacy at slowing or stopping hair loss rather than regrowing hair.

There are other considerations your healthcare provider may take into account. Since dutasteride is more effective at lowering DHT and is FDA-approved to treat benign prostatic hyperplasia (which is believed to be driven by DHT levels), it may be prescribed to treat both hair loss and BPH simultaneously (Nickel, 2004).

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Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Current version

June 26, 2020

Written by

Linnea Zielinski

Fact checked by

Mike Bohl, MD, MPH, ALM

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About the medical reviewer

Mike Bohl, MD, MPH, ALM

Dr. Mike is a licensed physician and a former Director, Medical Content & Education at Ro.