Comparative Effectiveness of Generic Versus Brand-Name Antiepileptic Medications

Epilepsy Behav. 2015 Nov;52(Pt A):14-8. doi: 10.1016/j.yebeh.2015.08.014. Epub 2015 Sep 19.

Abstract

Objective: The objective of this study was to compare treatment persistence and rates of seizure-related events in patients who initiate antiepileptic drug (AED) therapy with a generic versus a brand-name product.

Methods: We used linked electronic medical and pharmacy claims data to identify Medicare beneficiaries who initiated one of five AEDs (clonazepam, gabapentin, oxcarbazepine, phenytoin, zonisamide). We matched initiators of generic versus brand-name versions of these drugs using a propensity score that accounted for demographic, clinical, and health service utilization variables. We used a Cox proportional hazards model to compare rates of seizure-related emergency room (ER) visit or hospitalization (primary outcome) and ER visit for bone fracture or head injury (secondary outcome) between the matched generic and brand-name initiators. We also compared treatment persistence, measured as time to first 14-day treatment gap, between generic and brand-name initiators.

Results: We identified 19,760 AED initiators who met study eligibility criteria; 18,306 (93%) initiated a generic AED. In the matched cohort, we observed 47 seizure-related hospitalizations and ER visits among brand-name initiators and 31 events among generic initiators, corresponding to a hazard ratio of 0.53 (95% confidence interval, 0.30 to 0.96). Similar results were observed for the secondary clinical endpoint and across sensitivity analyses. Mean time to first treatment gap was 124.2 days (standard deviation [sd], 125.8) for brand-name initiators and 137.9 (sd, 148.6) for generic initiators.

Significance: Patients who initiated generic AEDs had fewer adverse seizure-related clinical outcomes and longer continuous treatment periods before experiencing a gap than those who initiated brand-name versions.

Keywords: Antiepileptic drugs; Comparative effectiveness; Generics.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aged
  • Anticonvulsants / adverse effects
  • Anticonvulsants / therapeutic use*
  • Cohort Studies
  • Drugs, Generic / adverse effects
  • Drugs, Generic / therapeutic use*
  • Electronic Health Records
  • Emergency Service, Hospital / statistics & numerical data
  • Endpoint Determination
  • Epilepsy / drug therapy*
  • Female
  • Humans
  • Male
  • Medical Record Linkage
  • Medicare
  • Pharmacies
  • Propensity Score
  • Socioeconomic Factors
  • United States

Substances

  • Anticonvulsants
  • Drugs, Generic