Impact of generic substitution on levetiracetam serum concentration-A prospective study in an outpatient setting.

Background: Switching patients from a branded antiepileptic drug (AED) to a generic is often challenging. Several studies have shown that considerable proportions of patients report deteriorated seizure control or increased adverse effects, enforcing a switchback to the original drug. Since tolerability and seizure control usually correlate with AED serum concentrations, we examined the fluctuation of levetiracetam (LEV) serum concentrations in patients with epilepsy before and after generic substitution.