5a-RIs therapy, while improving urinary symptoms in patients with BPH and may prevent hair loss, produce significant adverse effects in some individuals including loss of libido, ED, ejaculatory dysfunction, and potential depression. They are serious enough to preclude them from pursuing such therapy.... The effects of these agents on vascular health should also be noted in light of recent findings that patients treated with 5a-RIs therapy had significant adverse cardiovascular events.... These observations suggest that extreme caution should be exercised prior to prescribing 5a-RIs therapy to patients for hair growth or for BPH symptoms.
Traish AM, Hassani J, Guay AT, Zitzmann M, Hansen ML, et al. Adverse side effects of 5α-reductase inhibitors therapy: persistent diminished libido and erectile dysfunction and depression in a subset of patients. J Sex Med. 2011 Mar;8(3):872-84. doi: 10.1111/j.1743-6109.2010.02157.x. Epub 2010 Dec 22. [PubMed]