Describe reason(s) for inadequate trials of Anti-Seizure Medications (ASMs) in people with newly diagnosed and treated focal epilepsy who have not achieved seizure freedom (defined by International League Against Epilepsy, ILAE, as > 3X prior inter-seizure interval).

The ILAE defines treatment resistance (TR) as ongoing seizures despite two “adequate” ASM trials (appropriate dosing with appropriate ASM). We explored how often and why treatment resistance could not be determined because two adequate trials were never provided, and explored reasons for potential undertreatment.

We used data from the Human Epilepsy Project (HEP) , an international cohort study that enrolled patients with newly diagnosed focal epilepsy within 4 months of starting ASM treatment. ASM data was obtained from case report forms and medical records. Seizure data was derived from prospective diaries and supplemented with medical records.

448 patients were enrolled in HEP. 52 subjects with ongoing seizures had <2 adequate ASM trials. 31 subjects (59.62% ) tried 1 ASM, of which 4 had inadequate doses. The main reasons for no additional ASM trials were perception of seizure control (n=8, 24.2%) and poor communication/non-adherence (n=7, 21.2%). 21 (40.4%) tried >1 ASM with only one considered adequate dose (2 ASMs: n=15, 28.85%; >3 ASMs: n=6, 11.54%). Reasons for no additional ASM trials included perception of seizure control (n=9, 17.3%), patient preference despite poor efficacy (n=4, 7.69%), infrequent seizures(n=6, 11.5%), and ongoing titration (n=11, 21.2%). 4 subjects reported insurance as a reason for not trying additional ASMs.

Using ILAE criteria, >10% of people could not be categorized as treatment-resistant despite ongoing seizures. In some cases, it appears that patient/physician accepted ongoing seizures rather than switching to a new ASM.