Are 5-alpha reductase blockers safe?


Despite how common it is, male pattern hair loss is something that exactly no one looks forward to. About 70% of men are expected to be affected at some point throughout life (1).  That’s about 35 million men in the United States at any given time. The best part is, as we all know, once hair loss starts, it usually only gets worse with age. It’s not all bad news though as there is treatment, especially when started early. Camouflage and concealers are an option. These will not prevent hair loss but can effectively hide it through use of hair thickening fibers for individuals with thinning hair. For those with larger areas to conceal, hair pieces or specialized tattooing is an option. Hair transplant surgery is also a very effective technique (2) but can be price-limiting. Therefore, many men rely on medication for hair regrowth and to prevent further loss. To support this demand, there are exactly two drugs that are currently FDA approved to treat hair loss (3).  The first is minoxidil. It is popular as it has been shown to promote hair growth (4) but some find the daily topical applications to be time-consuming and cumbersome. For this reason, the second drug, finasteride, has become a cornerstone in men’s health. The mechanism of action is different from minoxidil so the two can be used in combination plus, there are no messy applications with finasteride and it has been shown to promote hair growth (5). Finasteride, and its cousin dutasteride, are 5 α-reductase inhibitors which work to prevent the hormone changes that can cause hair follicle shrinkage and disappearance (6).

What’s the catch?

With multiple options available for hair loss treatment, this may seem like great news. The catch is that finasteride has become associated with some serious side effects, leaving only one choice for those who want non-surgical hair growth. Suspected side effects include fatigue, muscle weakness, and cognitive problems in combination with sexual dysfunction (7,8). Reports of these side effects are very rare however and conflict with clinical observations that finasteride is safe (9). Despite this, and due to the significance of the suggested side effects, you might still be wondering if finasteride is safe.


In reality, most of the hair loss studies that link finasteride to sexual dysfunction have been criticized for bias. In fact many problems with these studies have been discussed, including methodology, use of an inappropriate patient population and lack of controls (important for validating and analyzing the data). Nonetheless, as the suggested side effects are severe, they have been recently investigated. Multiple studies, specifically targeting the potential for sexual side effects, found no correlation or association with finasteride use (10,11).

The presence of a nocebo effect has also been suggested. A nocebo effect is like the opposite of a placebo effect. Instead of feeling mysteriously better after taking a sugar pill or some other sham treatment, patients displaying the nocebo effect will develop a complication or become ill. With finasteride it has been shown that the patients who are counselled on the possibility of sexual side effects are the patients significantly more likely to develop them (12). Therefore, the nocebo effect was suggested as an explanation for some of the increased reports of side effects.


Overall, finasteride has been shown to be effective in preventing hair loss (13). Reports of finasteride and sexual dysfunction are rare, with lots of evidence showing that finasteride is safe. If you are interested in trying finasteride, the best course of action is to talk to your doctor or health care provider. If not, there are some new treatments available known for little to no side effects which include laser therapy and platelet-rich plasma therapy (14,15). We can also be hopeful that in the future there will be even more options to choose from.

Article by: Dr. J.L. Carviel, Mediprobe Research


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