Prevalence and cost of nonadherence to antiepileptic drugs in elderly patients with epilepsy.

Retrospective insurance claims from the United States were analyzed to assess nonadherence to antiepileptic drugs (AEDs) and the association between AED nonadherence, seizures, and health care costs in elderly persons with epilepsy. Inclusion criteria were: age 65, epilepsy diagnosis between 1 January 2000 and 31 June 2006, 2 AED prescriptions, and insurance enrollment for 6 months pre- and 12 months post-AED initiation. Adherence was evaluated using the medication possession ratio (MPR), with MPR<0.