Finasteride-Induced Recurrent Aphthous Ulceration-Like Lesions: A Case Report with Dechallenge-Rechallenge Confirmation

This case report documents the first known instance of finasteride, a medication commonly used for male androgenetic alopecia, inducing recurrent aphthous ulceration (RAU)-like lesions in a 45-year-old male pharmacist. The patient experienced painful oral ulcers two to three times per month over six years of finasteride use, which resolved upon discontinuation of the drug and recurred upon rechallenge. Comprehensive investigations ruled out other potential causes, and a Naranjo score of 8 indicated a probable causal relationship, while the WHO-UMC system confirmed a "certain" causal link. Clinicians are advised to consider finasteride as a potential cause in patients with unexplained recurrent oral ulceration.