[10][11] Exposure during pregnancy is specifically contraindicated because antiandrogens such as dutasteride have been shown to interfere with the sexual development of male fetuses.

[15] A 2010 Cochrane review found a 25–26% reduction in the risk of developing prostate cancer with 5α-reductase inhibitor chemoprevention.

[16] Dutasteride is approved for the treatment of male androgenetic alopecia in South Korea and Japan at a dosage of 0.5 mg per day.

[6][17] Several studies have found it to induce hair regrowth in men more rapidly and to a greater extent than even the highest approved dosage of finasteride.

However, dutasteride is not recommended for this indication due to a lack of supportive clinical evidence and a substantial risk of birth defects in female patients who inadvertently become pregnant.

[23][24] Dutasteride is sometimes used as a component of hormone therapy for transgender women in combination with an estrogen and/or another antiandrogen such as spironolactone.

[27] A small risk of sexual side effects has been documented in men taking the drug during the first few months of therapy.

[27][28] The FDA added a black-box warning to dutasteride in 2011 describing an increased risk of high-grade prostate cancer in those who take the drug.

The American Urological Association advises that increased risk for patients taking these drugs leads to higher prostate cancer-specific and all-cause mortality.

[30] The AUA also advises that this affect can be alleviated with more frequent screening and lower PSA cutoffs for diagnostic biopsies in men taking dutasteride or other 5α-reductase inhibitors.

[33] Sexual and mood side effects, such as erectile dysfunction,[34] loss of libido,[35] depression,[36] and reduced semen volume occur in as many as 4.8% of patients taking 5α-reductase inhibitors including dutasteride.

[11] A subset of men affected by sexual and mood side effects report persistent loss of libido,[34] depression,[27] and erectile dysfunction for several years after discontinuing treatment.

[30][45][46] The Post-Finasteride Syndrome Foundation (PFSF) was created with a medical advisory board to study the topic (finasteride is a similar 5α-reductase inhibitor)[47] and lawsuits alleging harm from the drug are ongoing.

[48] Concerns from the PFSF and other patient advocates led the FDA to add a black-box warning to Finasteride for possible risks of suicide in June 2022.

[30][49] Some experts have questioned the basis of the black-box warning, given that it relies on anecdotal patient-reported outcomes rather than prospective trials.

[54][55] Dutasteride belongs to a class of drugs called 5α-reductase inhibitors, which block the action of the 5α-reductase enzymes that convert testosterone into DHT.

[37] These neurosteroids are potent positive allosteric modulators of the GABAA receptor and have shown antidepressant, anxiolytic, and pro-sexual effects in animal research.

[37][64][65] For this reason, decreased neurosteroid production is one hypothesized mechanism for sexual dysfunction and depression associated with 5α-reductase inhibitors such as dutasteride.

[68][69] It was approved by the FDA for the treatment of BPH in November 2001, and was introduced on the United States market the following year under the brand name Avodart.

[69] The patent protection of dutasteride expired in November 2015, so the drug has since become available in the United States in a variety of low-cost generic formulations.