Abstracts

Rationale: The International League Against Epilepsy (ILAE) defines drug resistant epilepsy (DRE) as failure of an adequate trial of two tolerated, appropriately chosen and used antiepileptic drug (AED) schedules to achieve seizure freedom. The ILAE task force that was set up to define DRE did not specify dosages at which therapy was determined to have failed for any of the AEDs available at the time. The World Health Organization (WHO) has developed a statistical measure of drug consumption called the defined daily dose (DDD) to standardize the comparison of drug usage between different drugs within the same class. DDD is the assumed average maintenance dose per day for a drug used for its main indication in adults. We investigated AED response in veterans with DRE utilizing DDD as an objective measure.  Methods: We conducted a retrospective chart review of all veterans seen in Seizure Clinic at the Veterans Affairs West Los Angeles Healthcare Center from 7/1/2008 to 6/30/2017. Patients with DRE were included in the analysis. DRE status was determined based on ILAE criteria. Daily doses were recorded for each AED and chronologically ordered per patient. The doses were recorded as a percent of DDD. Responses to each of the AEDs were recorded using ILAE drug response criteria. Additional data points collected included baseline characteristics, duration of epilepsy, history of TBI, comorbid disease states, and response to AEDs with respect to seizure control and side effects. Patients with psychogenic non-epileptic seizures were excluded from our study.  Results: To date we have reviewed 483 charts. Of the 483 charts reviewed, 203 (42%) met inclusion criteria. Mean duration of epilepsy was 21 years. The 203 patients were exposed to 744 AEDs. When AEDs were stratified by dose range, in patients prescribed up to 100% of DDD, 51% of the AEDs were found to be effective. This was similar to the group prescribed greater than 100% of DDD as 50% of the AEDs were also found to be effective. The top 3 AEDs prescribed were levetiracetam, phenytoin, and lamotrigine. Levetiracetam was prescribed in 127 patients who received a mean of 1.49 DDD with 46% of patients responding to the drug. Phenytoin was prescribed in 113 patients who received a mean of 1.25 DDD with 29% of patients responding to the drug. Lamotrigine was prescribed in 77 patients who received a mean of 0.95 of DDD with 30% of patients responding to the drug. Analysis is ongoing for subsequent AEDs.  Conclusions: When comparing AED doses below DDD with AED doses above DDD, we found no difference in effectiveness of the AEDs. Funding: No funding