Adherence and Costs among Epilepsy Regimens

Anaheim—A study found that patients with epilepsy who received a non-controlled antiepileptic drug (AED) had stronger medication adherence and lower total medical costs compared with patients treated with controlled AEDs.

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Several AEDs are classified as controlled substances by the FDA. The recent study analyzed the potential impact of initiating treatment with a controlled AED and its affect on adherence and costs. The study was presented at the ASHP meeting during a poster session titled Adherence and Medical Costs Among Patients with Epilepsy Receiving AEDs Classified as Controlled Substances: An Analysis of a Large Administrative Claims Database.

The retrospective database study used information from the 2006 to 2012 PharMetrics Plus Database.

Patients were included in the study if they were ≥18 years of age and had ≥1 inpatient or ≥2 outpatient claims with a diagnosis of epilepsy according to the International Classification of Diseases, 9th Revision. Patients also had to have treatment with ≥1 AED following the first epilepsy claim, with the first AED prescription representing the index date. Patients had to have continuous eligibility 1 year prior to baseline and 1 year following the index date.

The study examined adherence to any AED medication, which was defined as a medication possession rate (MPR) ≥0.8. All-case medical and pharmacy costs were also examined during follow-up. A logistic regression and generalized linear model were used to assess the impact of controlled and non-controlled AEDs on adherence and total costs.

A total of 30,592 patients were included in the study, and 10.3% of the study population (n=3146) initiated treatment with a controlled AED. The mean age of patients included in the study was 47 years for both treatment cohorts.

The study found that 38.3% of patients who initiated treatment with a controlled AED had a prescription for a non-controlled AED during the 1-year follow-up period, while 17.8% of patients who initiated treatment with a non-controlled AED had a prescription for a controlled AED during the 1-year follow-up.

By comparison, 67% of patients taking a controlled AED were nonadherent to their medication compared with 54% of those on a non-controlled AED.

Patients who initiated treatment with a controlled AED had a lower MPR compared with patients taking non-controlled AEDs (0.52 vs 0.64, respectively; P<.01). In addition, a lower proportion of patients taking a controlled AED were adherent to any AED medication compared with those on non-controlled AEDs (32.6% vs 46.3%, respectively; P<.01).

Patients who were taking controlled AEDs had a lower index-specific MPR compared with those on non-controlled AEDs (0.43 vs 0.63, respectively).

In terms of cost, the average total cost of a controlled AED was $22,528 versus $22,034 for a non-controlled AED (P<.01).

In a multivariate analyses, a statistically significantly higher probability of adherence to any AED (P<.01) and 6.7% lower total costs (P<.01) were seen in patients taking non-controlled AEDs.

The study’s authors indicated limitations, including potential coding errors and incomplete data. In addition, claims data provides reliable information on prescription refill information, though true medication adherence cannot be directly measured in this way; therefore, adherence may be overestimated in these findings.

In conclusion, the study’s authors suggested that additional research be conducted to assess the medical and economic outcomes associated with controlled and non-controlled AED use for patients with epilepsy.—Kerri Fitzgerald

Research support received from Sunovian Pharmaceuticals, Inc.