A Cochrane review assessed different medical interventions for hirsutism. Finasteride 5mg to 7.5 mg daily was more effective than placebo in reducing Ferriman-Gallwey scores (score 0 to 36) (MD -5.73, 95% CI -6.87 to -4.58). Spironolactone showed similar effectiveness to finasteride (MD 1.49, 95% CI -0.58 to 3.56 and MD 0.40, 95% CI -1.18 to 1.98; 2 trials). However, results were inconsisntent when comparing finasteride with flutamide.
A topic in Clinical Evidence summarizes the results of 2 RCTs. The first RCT (n=24 women, 14 with polycystic ovary syndrome) found that finasteride 5 mg daily significantly reduced hirsutism compared with placebo (Ferriman-Gallwey score 6.7 vs 10.6, p<0.01). The second RCT (n=40, 21 with polycystic ovary syndrome) found that finasteride, spironolactone, and flutamide reduced hirsutism compared with placebo (p<0.01 for all treatments).
Comment: The quality of evidence is downgraded by study quality and by sparse data.