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Factors Associated with Seizure Recurrence in Epilepsy Patients Treated with Antiepileptic Monotherapy: A Retrospective Observational Cohort Study using US Administrative Insurance Claims

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Abstract

Background

Few studies examine predictors of seizures in medically treated patients with epilepsy receiving antiepileptic monotherapy using a large patient population.

Objective

Our objective was to identify clinical, medication, and demographic factors associated with seizure recurrence in medically treated patients with epilepsy receiving one of four antiepileptic monotherapy regimens: lamotrigine, levetiracetam, oxcarbazepine, or topiramate.

Study Design

A retrospective cohort study was conducted using Innovus Invision™ Data Mart paid medical and prescription US commercial insurance claims data from January 2007 to September 2010.

Methods

Patients aged 18–64 years with a primary or secondary diagnosis of epilepsy and one or more prescription claim for an antiepileptic drug (AED) pre-index were included. The primary outcome was incidence of a seizure or seizure-related event, defined as an emergency room visit, ambulance service use, or inpatient hospitalization medical claim with a primary or secondary diagnosis of epilepsy during the 1-year follow-up. The factors included AED adherence, somatic comorbidity (measured via Charlson Comorbidity Index), mental health comorbidity, pre-index seizure, type of epilepsy diagnosis, presence of AED-interacting medications and any bioequivalent AED switch. The covariates included age, gender, and geographic region of residence.

Results

A total of 5.3 % (166/3,140) of patients on AED monotherapy had experienced a seizure or a seizure-related event requiring urgent care at 1-year follow-up. The multivariate analysis of the combined cohort showed that pre-index seizures/seizure-related events (odds ratio [OR] 4.23; 95 % confidence interval [CI] 2.77–6.46), any mental health comorbidity (OR 3.50; 95 % CI 2.14–5.70), and Charlson Comorbidity Index ≥1 (OR 2.91; 95 % CI 1.98–4.28) were significantly associated with post-index seizures/seizure-related events. Patients residing in Northeastern USA had a higher likelihood of a post-index seizure (OR 1.90; 95 % CI 1.17–3.08) than patients residing in the Southern region of the USA. Bioequivalent AED switch, type of epilepsy diagnosis, AED adherence, and presence of AED-interacting medications were not associated with seizure recurrence in the combined cohort analysis (p > 0.05).

Conclusions

Epilepsy patients with comorbid conditions (both mental and somatic diseases) and prior seizures were more likely to experience seizures at 1-year follow-up. Non-adherent patients and patients with bioequivalent AED switches appeared to show no increased likelihood of seizure at follow-up. Clinicians may consider these findings before starting or transitioning to an AED monotherapy.

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Acknowledgments

The authors would like to acknowledge assistance provided by Woody Zachry, Ph.D., in securing access to the dataset for this study. This study did not receive any external funding. The results of this study were presented in part at the annual meetings of the American Pharmacists Association in Los Angeles, CA, USA, 3 March 2013 and the ISPOR in New Orleans, LA, USA, 20 May 2013. Dr. Shcherbakova has no conflicts of interest. Dr. Rascati has no conflicts of interest. Dr. Brown has no conflicts of interest. Dr. Lawson has no conflicts of interest; he has received grant funding from Shire Development and Abbott Laboratories for unrelated projects. Dr. Novak has no conflicts of interest. Dr. Richards has no conflicts of interest. Dr. Yoder has no conflicts of interest.

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Authors and Affiliations

  1. Department of Pharmaceutical and Administrative Sciences, College of Pharmacy, Western New England University, 1215 Wilbraham Road, Springfield, MA, 01119, USA

    Natalia Shcherbakova

  2. Division of Health Outcomes and Pharmacy Practice, College of Pharmacy, The University of Texas at Austin, 1 University Station A1900, Austin, TX, 78712, USA

    Karen Rascati, Carolyn Brown, Kenneth Lawson, Suzanne Novak & Kristin M. Richards

  3. School of Nursing, The University of Texas at Austin, 1700 Red River St, Austin, TX, 78701, USA

    Linda Yoder

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  1. Natalia Shcherbakova
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  2. Karen Rascati
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Correspondence to Natalia Shcherbakova.

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Shcherbakova, N., Rascati, K., Brown, C. et al. Factors Associated with Seizure Recurrence in Epilepsy Patients Treated with Antiepileptic Monotherapy: A Retrospective Observational Cohort Study using US Administrative Insurance Claims. CNS Drugs 28, 1047–1058 (2014). https://doi.org/10.1007/s40263-014-0191-1

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