To quantify reports made to the Food and Drug Administration Adverse Event Reporting System (FAERS), create a demographic of patient reports, and examine the cluster of symptoms to correlate consistency of postfinasteride syndrome (PFS) complaints. PFS is a provisional diagnosis encompassing a cluster of sexual, physical, and psychological and/or neurologic symptoms associated with 5-alpha reductase inhibitor use that emerge or continue after discontinuation of medication.

FAERS dataset of 5-alpha reductase inhibitors from April 2011 to October 2014 was obtained. Each FAERS report had 16 categories for completion, but not every report was fully completed. Statistical analysis compared variables of interest between the 2 doses of finasteride (1mg vs 5 mg).

From FAERS, 2048 monotherapy cases were identified: 1581 of finasteride 1mg, 240 of finasteride 5mg, and 226 of unreported doses. Possibly related to labeling changes, from 2011 to 2014, there was a significant increase in adverse events (AEs) reported involving 1mg dosing. Finasteride use was reported with many sexual AEs including diminished libido, erectile dysfunction, and ejaculatory complaints. Other common AEs included dermatologic, metabolic, and psychological and/or neurologic complaints. There were more AE reports with the 1mg dose than the 5mg dose. One case of dutasteride reported back pain, not generally attributed to PFS.

FAERS data suggests that finasteride exposure is reported with a diverse collection of symptoms, particularly in younger men on 1mg dosage compared to older men on 5mg. Many of these complaints fall well out of the realm of previously established AEs from long-term controlled studies.