Risks Associated with 5α-Reductase Inhibitor Use: Analysis of Adverse Drug Reactions Reported to EudraVigilance

Background/Objectives: 5α-Reductase inhibitors (5ARIs) are commonly used to treat and prevent androgenic alopecia and benign prostatic hyperplasia. Despite their well-established effectiveness, they are associated with adverse drug reactions (ADRs), highlighting the need for continuous safety assessment. This study aimed to analyze the ADRs associated with finasteride and dutasteride, both as monotherapy and in combination therapy. Methods: A retrospective analysis of ADRs associated with finasteride and dutasteride reported to EudraVigilance between 1 January 2005 and 27 March 2023 was performed. A total of 7777 reports were selected, and various variables were examined, including the temporal evolution of ADR reports, reporter profile, and the age group of the affected population. ADRs were categorized based on their seriousness and outcome, with particular focus on the most common reactions and their alignment with the Summary of Product Characteristics (SmPC). Results: The most affected age group, excluding the "Not Specified" category, was "18-64 years." Overall, finasteride was the most reported. The majority of reported ADRs were classified as "Serious," with a predominant outcome of "Persists without recovery," and a significant proportion of these ADRs were not listed in the respective 5ARI SmPCs. Among the ADRs classified as "Serious," the most frequently reported seriousness criterion was "Clinically important". Conclusions: The results emphasize how crucial it is to continuously monitor these drugs in order to prevent and mitigate ADRs, ensure population safety, and promote public health. Additionally, more research is required to determine whether the ADRs not included in the SmPC could be new warning signs.