Abstracts

Rationale: Adherence to antiepileptic drug (AED) treatment is a key modifiable factor in seizure control among patients with epilepsy. The contribution of attention deficit and other psychiatric disorders to AED non-adherence has not been widely studied in pediatric patients with epilepsy. The purpose of this study is to understand the role of psychiatric comorbidity on AED non-adherence in pediatric patients with epilepsy. Methods: Retrospective claims of pediatric managed care enrollees from the PharMetrics database (1/1/00-12/31/06) were analyzed. Inclusion criteria were: age 4 to18 years; ≥1 diagnosis of epilepsy or non-febrile convulsions; ≥1 AED prescription; and continuous health plan enrollment for ≥12 months prior to and following AED initiation. Adherence was measured using the medication possession ratio (MPR), defined as the sum of AED days supplied during 12 months following initiation divided by the number of days (365) in the follow-up period. Patients with an MPR ≤0.8 were classified as non-adherent. Multivariate analyses were used to estimate the effect of attention deficit disorder (ADD), attention deficit hyperactivity disorder (ADHD), and serious mental illnesses (SMIs) on MPR and likelihood of adherence. Covariates included age, gender, geographic region, overall comorbidity burden, AED type initiated (newer vs. older), initial AED regimen (combination vs. monotherapy), and initial AED pill count (>1 vs. ≤1 pill per day). Results: 5,343 subjects (55% male, 48% age 4 to 11 years) met all inclusion criteria. Two thirds initiated a newer AED, and nearly all subjects (95%) initiated a monotherapy regimen. Mean MPR was 0.542, and 65% of subjects were non-adherent. ADD and ADHD were seen in 10% and 17% of subjects, respectively, while 23% had at least one SMI. Among those with an SMI, bipolar disorder was the most prevalent, seen in 44% of subjects. Having a prior history of ADHD was associated with a 17% increased likelihood of non-adherence (odds ratio [OR]=1.167, P=0.049). Presence of schizophrenia following AED initiation was associated with an 11 percentage point reduction in the MPR (P=0.015), but had no effect on the likelihood of having an MPR of ≥0.8. History of bipolar disorder, as well as presence following AED initiation, was associated with a 22% increased likelihood of non-adherence (OR=1.224, P=0.028). While no other SMIs, including major depression, manic disorder, autism, and other psychoses had a significant impact on adherence, presence of at least one SMI was associated with a 15% increased likelihood of AED non-adherence (OR=1.148, P=0.041). Conclusions: These data suggest that adherence to AEDs is sub-optimal in pediatric patients with epilepsy. Having a history of ADHD or presence of an SMI, particularly schizophrenia or bipolar disorder, may be key factors contributing to low adherence. Clinicians may need to consider these specific psychiatric comorbidities in the management and care of pediatric epilepsy.