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Outcomes after changing antiepileptic drugs (AEDs) have largely been studied in single cohort series. We recently reported the first study to examine this question in a controlled manner. Here we expand on these results by using a matched, prospective methodology applied to both uncontrolled and well-controlled patients taking any AED.

We reviewed all outpatient notes over a 9-month period and identified patients with focal epilepsy who were on monotherapy. We classified those who switched AEDs as case patients, with those remaining on the same drug serving as controls. We matched cases with controls for seizure status (seizure-free in the preceding 6 months or not), current AED, and number of failed AEDs. We subsequently assessed outcome 6 months later.

Seizure-free patients who switched drug (n = 12) had a 16.7% rate of seizure recurrence at 6 months, compared to 2.8% among controls remaining on the same drug (n = 36, p = 0.11). There was a 37% remission rate among uncontrolled patients who switched drug compared to 55.6% among controls (n = 27 per group, p = 0.18). Uncontrolled patients who had previously tried more than one AED were somewhat less likely to enter remission (p = 0.057). Neither AED mechanism of action nor change in dosage impacted outcome.

Herein we provide further estimation of the modest risk (~14%) associated with switching AEDs in patients in remission compared to being maintained on the same regimen. Uncontrolled patients were no more likely to enter remission after a drug switch than they were after remaining on the same drug, suggesting that spontaneous changes in disease state, and not drug response, underlie remission in this population.