Pharmacological Inhibition of 5α-Reductase in Androgenetic Alopecia: A Comparative Narrative Review of Finasteride and Dutasteride, with Attention to Responder Heterogeneity and Female Pattern Hair Loss

This narrative review compares finasteride and dutasteride, two 5α-reductase inhibitors used in treating androgenetic alopecia (AGA) in both men and women. Finasteride reduces serum dihydrotestosterone (DHT) by about 70%, while dutasteride achieves a deeper suppression of approximately 90%, leading to slightly greater hair count improvements. A pivotal trial showed dutasteride at 2.5 mg was superior to finasteride at 5 mg, but the 0.5 mg dose of dutasteride is standard due to its efficacy and tolerability. Genetic factors, particularly androgen receptor variations, significantly influence treatment response. In women, higher doses of finasteride and variable doses of dutasteride are supported, especially in postmenopausal and some premenopausal groups. The review highlights the need for further research into genetic modifiers of response and emphasizes the importance of informed consent regarding post-finasteride syndrome.