Finasteride-Its Impact on Sexual Function and Prostate Cancer

Finasteride, a specific and competitive inhibitor of 5α-reductase enzyme Type 2, inhibits the conversion of testosterone to dihydrotestosterone (DHT). In adults, DHT acts as primary androgen in prostate and hair follicles. The only FDA-approved dermatological indication of finasteride is androgenetic alopecia. But, apprehension regarding sexual dysfunction associated with finasteride deters dermatologists from prescribing the drug and patients from taking the drug for androgenetic alopecia. Testosterone, through its humoral endocrine and local paracrine effects is relevant in central and peripheral modulation of sexual function than locally acting DHT. Several large population-based long-term placebo-controlled studies, using International Index of Erectile Function-5 questionnaire and objective method (Nocturnal Penile Tumescence) to assess the erectile function have demonstrated no clear evidence of the negative effect of finasteride on erectile function. Reduction in ejaculatory volume is the only established causal relationship between finasteride and sexual dysfunction. Though finasteride causes significant reduction in all the semen parameters except sperm morphology, they did not fall below the threshold levels to interfere with fertility. Therefore, the sexual adverse effects associated with finasteride should be viewed in relation to normal prevalence and natural history of erectile dysfunction in the population, age of the patient, other confounding factors and also nocebo effect. The impact of finasteride on the prevention of prostate cancer has been discussed extensively. Finasteride is found to be effective in significantly reducing the incidence of low-grade prostate cancer. But the paradoxical increase in high-grade cancer in the finasteride group has been attributed to increased sensitivity and improved performance of prostate specific antigen levels to detect all grades of prostate cancer.