Case-control analysis of ambulance, emergency room, or inpatient hospital events for epilepsy and antiepileptic drug formulation changes

Epilepsia. 2009 Mar;50(3):493-500. doi: 10.1111/j.1528-1167.2008.01703.x. Epub 2008 Jun 26.


Purpose: Although antiepileptic drugs (AEDs) with multisource generic alternatives are becoming more prevalent, no case-control studies have been published examining multisource medication use and epilepsy-related outcomes. This study evaluated the association between inpatient/emergency epilepsy care and the occurrence of a recent switch in AED formulation.

Methods: A case-control analysis was conducted utilizing the Ingenix LabRx Database. Eligible patients were 12-64 years of age, received >or=145 days of AEDs in the preindex period, had continuous eligibility for 6 months preindex, and no prior inpatient/emergency care. Cases received care between 7/1/2006 and 12/31/2006 in an ambulance, emergency room, or inpatient hospital with a primary epilepsy diagnosis. Controls had a primary epilepsy diagnosis in a physician's office during the same period. The index date was the earliest occurrence of care in each respective setting. Cases and controls were matched 1:3 by epilepsy diagnosis and age. Odds of a switch between "A-rated" AEDs within 6 months prior to index were calculated.

Results: Cases (n = 416) had 81% greater odds of having had an A-rated AED formulation switch [odds ratio (OR) = 1.81; 95% confidence interval (CI) = 1.25 to 2.63] relative to controls (n = 1248). There were no significant differences between groups regarding demographics or diagnosis. Significant differences were found with regard to medical coverage type (case Medicaid = 4.6%, control Medicaid = 1.8%, p = 0.002). Post hoc analysis results excluding Medicaid recipients remained significant and concordant with the original analysis.

Discussion: This analysis found an association between patients receiving epilepsy care in an emergency or inpatient setting and the recent occurrence of AED formulation switching involving A-rated generics.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Ambulances*
  • Anticonvulsants / adverse effects
  • Anticonvulsants / economics
  • Anticonvulsants / therapeutic use*
  • Case-Control Studies
  • Cost Savings
  • Drug Costs / statistics & numerical data
  • Drugs, Generic / adverse effects
  • Drugs, Generic / economics
  • Drugs, Generic / therapeutic use*
  • Emergency Medical Services*
  • Emergency Service, Hospital*
  • Epilepsies, Partial / diagnosis
  • Epilepsies, Partial / drug therapy*
  • Epilepsies, Partial / economics
  • Epilepsy, Generalized / diagnosis
  • Epilepsy, Generalized / drug therapy*
  • Epilepsy, Generalized / economics
  • Female
  • Humans
  • Isoxazoles / adverse effects
  • Isoxazoles / economics
  • Isoxazoles / therapeutic use*
  • Male
  • Medicaid / economics
  • Middle Aged
  • Odds Ratio
  • Patient Admission*
  • Retrospective Studies
  • Therapeutic Equivalency
  • Treatment Outcome
  • United States
  • Young Adult
  • Zonisamide


  • Anticonvulsants
  • Drugs, Generic
  • Isoxazoles
  • Zonisamide