Finasteride and dutasteride, both 5-alpha reductase inhibitors, are considered first-line treatment for androgenetic hair loss in men and used increasingly in women. In each case, patients are expected to take the medications indefinitely despite the lack of research regarding long-term adverse effects. Concerns regarding the adverse effects of these medications has led the United States National Institutes of Health to add a link for post-finasteride syndrome to its Genetic and Rare Disease Information Center. Herein, the authors report the results of a literature search reviewing adverse events of 5-alpha reductase inhibitors as they relate to prostate cancer, psychological effects, sexual health, and use in women. Several large studies found no increase in incidence of prostate cancer, a possible increase of high-grade cancer when detected, and no change in survival rate with 5-alpha reductase inhibitor use. Currently, there is no direct link between 5-alpha reductase inhibitor use and depression; however, several small studies have led to depression being listed as a side effect on the medication packaging. Sexual effects including erectile dysfunction and decreased libido and ejaculate were reported in as many as 3.4 to 15.8 percent of men. To date, there are very few studies evaluating 5-alpha reductase inhibitor use in women. Risks include birth defects in male fetuses if used in pregnancy, decreased libido, headache, gastrointestinal discomfort, and isolated reports of changes in menstruation, acne, and dizziness. Overall, 5-alpha reductase inhibitors were well-tolerated in both men and women, but not without risk, highlighting the importance of patient education prior to treatment.
Dermatologists as well as primary care physicians widely use finasteride and dutasteride as a first-line treatment for male and female pattern hair loss. Presently there is a lack of research regarding long-term adverse effects of these medications, despite the fact that patients are expected to take them indefinitely to maintain hair growth. Concerns regarding the adverse effects of finasteride and dutasteride has led the United States National Institutes of Health to add a link for post-finasteride syndrome to its Genetic and Rare Disease Information Center website. Of the current literature, the majority of research examining the side effects of these medications are at higher doses intended to treat conditions such as benign prostatic hyperplasia rather than the lower doses commonly used in dermatology for hair loss. Furthermore, 5-alpha reductase inhibitor (5ARI) use in women has been limited due to a lack of research examining adverse reactions in this patient population. Herein, the authors present the results of a literature review examining the side effects of both finasteride and dutasteride. Androgenetic alopecia (AGA) is a hereditary pattern of hair loss where terminal hairs are converted into miniaturized vellus hairs.1 This type of hair loss is very common with reports showing up to 80 percent of Caucasian men and 50 percent of women showing evidence of AGA by 70 years of age.2,3 Men and women, however, typically exhibit different patterns of hair loss. Men tend to have thinning of the hairs in the frontotemporal scalp and scalp vertex, whereas women show thinning of the central scalp.1 The hair loss seen can lead to a large amount of emotional distress and affect a patient’s quality of life in a negative way leading them to seek treatment.4-6 5-alpha reductase (5AR) inhibitors, such as finasteride and dutasteride, are commonly used to stabilize hair loss and promote regrowth. The androgen dihydrotestosterone (DHT) is thought to play a large role in inducing AGA and is formed from the conversion of circulating testosterone to DHT by 5AR. Current therapy for AGA is aimed at blocking this conversion at the tissue level. There are three known isoenzymes of 5AR receptors5 with types I and II playing an important role in the treatment of AGA. Type I 5AR is located predominantly in the skin, including sebaceous glands and hair follicles, whereas type II is the major contributor to the DHT pool7 and is located in the inner root sheath of hair follicles in the scalp, beard, and chest as well as the genitals and prostate gland.1,5,8 Of the three isoforms of 5AR, dutasteride inhibits both type I and II, whereas finasteride inhibits only type II. Additionally, dutasteride is three times more potent than finasteride at inhibiting type II and 100 times more potent at inhibiting type I.9