Medication-associated priapism events: validation of findings from the FDA pharmacovigilance database using insurance claim database

Pharmacovigilance databases are important for tracking rare adverse events associated with medications. Approximately 51 new drugs are approved each year by the United States Federal Drug Agency and rare adverse events may be too infrequent to be detected in pre-approval clinical trials, thus the importance of these ongoing pharmacovigilance databases. Using the Federal Drug Agency pharmacovigilance databases, Schifano et al. found trazadone, olanzapine, and tadalafil had a higher risk of causing priapism compared to other medications within this database. We attempted to validate these findings using a large US claims database to assess the frequency of priapism diagnosis within 6 months of prescribing medications identified by Schifano et al. (trazodone, quetiapine, risperidone, olanzapine, aripiprazole, tadalafil, sertraline, sildenafil, methylphenidate, alprostadil, and clozapine). On propensity-matched retrospective cohort analysis with 3.4 million men exposed to the drugs of interest with 3.4 million propensity-matched controls. We find that trazadone and tadalafil were associated with increased risk of priapism – risk ratio [RR] 1.73, 95% Confidence Interval [CI] 1.28–2.34 and (RR: 3.00, 95% CI 2.19–4.11), respectively. Sildenafil was also found to be associated with increased risk of priapism diagnosis (RR: 1.77, 95% CI 1.37–2.29). The antipsychotic quetiapine, a second-generation antipsychotic like olanzapine, had the greatest association with a diagnosis of priapism (RR 3.50, 95% CI 1.93–6.34). Some analyses were unable to be performed, such as for alprostadil and olanzapine, as low number of patients having received a prescription for these medications resulted in a propensity-matched control group that was too small to accurately assess the risk ratio for the incidence of priapism. We confirm the findings of Schifano et al. describing the increased risk of priapism associated with prescriptions of trazadone, tadalafil, sildenafil, and second-generation antipsychotics.