Abstracts

Rationale: An estimated 1% of the population suffers from epileptic seizures. Despite newer drugs, many patients continue to be treated with older first-generation anti-epileptic drugs (AED’s ). Therapeutic ranges of AED’s are believed to confer good protection against breakthrough seizure, although the historic basis for these laboratory values is often anecdotal and not supported by rigorous clinical studies. Here, we evaluate anticonvulsant dosing among epileptic patients presenting to a large hospital Emergency Department to determine what role serum anticonvulsant levels play in medication dosing, and subsequent selection, if any, of an adjunctive agent. Methods: Over a two year period (2003-2005), the hospital database was used to identify randomly, Emergency Department (ED) records of adult patients presenting with breakthrough seizure and pre-existing diagnosis of epilepsy. Patients ranged in age from 18 to 91 years (median,49 years). ED charts were reviewed to capture those breakthrough patients and who had a prior existing AED regimen. 100 records were obtained, which also contained first generation serum levels. Results: Among charts reviewed, there were 82 occurrences of pre-existing prescriptions for first generation AED’s, with accompanying serum levels of the respective medication. The other 18 patients presented with no prior epilepsy diagnosis. Of the documented epileptic group, 50 patients' serum levels (61%) were within laboratory therapeutic range; and 27 patients' serum levels (33%) were in the sub-therapeutic range. The serum levels of 5 patients (6%) reflected a supra-therapeutic level. Within the laboratory therapeutic range group, 33 patient regimens (66%) were adjusted upward thereby increasing the already “therapeutic” dose of the first-generation compound. Within the sub-therapeutic group, 26 patients (96%) received an increased dose of the existing regimen, as would be expected. Only one patient was switched to a completely alternative AED in the ED setting. Conclusions: This study suggests that upon breakthrough presentation to an ED, the dose of the existing first-generation AED regimen is typically raised despite a “therapeutic” level. Indeed, the contemporary paradigm of first generation AED dosing is equivalent to that which is commonly utilized with the newer second generation compounds which do not have defined therapeutic ranges. In other words, upon breakthrough seizure, the patient’s existing dose of medication is customarily increased despite serum level, barring the presence of clear-cut supra-therapeutic levels. This retrospective study of breakthrough seizure patients demonstrates that the continued usage of older first generation AED’s remains common; and that acquisition of serum anticonvulsant levels remains customary. Once obtained, however, a therapeutic serum level does not significantly impact the treating physician’s tendency to increase the existing monotherapy regimen, nor predispose to the prescribing of an adjunctive agent as may confer additional seizure protection.