[T]opical finasteride can still cause systemic side effects and isn’t necessarily “safer” than using the medicine orally.

Oral finasteride went through clinical trials to get FDA approved for male pattern hair loss. No clinical trials have been done to get topical finasteride approved by the FDA. After reading the FDA warning, all adverse side effects of topical finasteride were similar to oral finasteride. The most important takeaway is that topical finasteride can still cause systemic side effects and isn’t necessarily “safer” than using the medicine orally.

—Dermatologists Sound Off on Topical Finasteride After FDA Alert, NewBeauty.com: April 29, 2025