Patterns in spontaneous adverse event reporting among branded and generic antiepileptic drugs

Spontaneous adverse event reports constitute an important source of information on previously unknown adverse reactions to marketed medicines. However, the dynamics of such reporting following generic introduction are poorly understood. Using adverse event reports on five antiepileptic drugs from the US Food and Drug Administration's Adverse Event Reporting System, we describe temporal trends in adverse event reporting before and after generic introduction, and survey the quality of product-identifying information contained therein. The majority of reports were sent by innovator drug manufacturers while few were sent by generic manufacturers, even when generics accounted for >90% of dispensed prescriptions. We manually reviewed narratives from 2,500 reports and found that the suspect product type (brand or generic) could not be determined in 84% of reports, while generic products (16%) were identified more often than brand-name products (<1%). These results suggest that pharmacovigilance stakeholders should act to promote more detailed reporting practices.