Abstracts

Generic anticonvulsant medications for treatment of pediatric epilepsy offer advantages, particularly in cost to patients. Brand name and generic formulations are often considered equivalent in efficacy and tolerability; we report three cases of suspected decreased tolerability and efficacy associated with generic formulations. Three patients treated for epilepsy at our institution were identified as experiencing differences in tolerability between generic and brand name gabapentin (GBP) formulations.
Case 1: 12-year old boy with idiopathic complex partial seizures, treated successfully with GBP monotherapy using name brand formulation (1800mg/day). After being seizure free for 3 years, he was switched to generic formulation, and subsequently developed adverse effects (fatigue, forgetfulness, declining academic performance), 1 month after switching. Resolution of adverse effects occurred after changing back to name brand.
Case 2: 16-year old boy with idiopathic complex partial seizures with secondary generalization, treated successfully with GBP monotherapy using name brand formulation (2400mg/day). He was switched to generic formulation after 7 months, during which time he was seizure free. He experienced break-through seizures without other provocation 2 weeks after changing formulations. He was switched back to name brand, with no further seizures 3 months after switch.
Case 3: 13-year old boy with idiopathic complex partial and generalized seizures treated with GBP as adjunctive therapy to valproic acid. Generic GBP was initiated (1000mg/day), with development of myoclonic seizures (1-2 per day) and behavioral problems shortly thereafter. He was switched to name brand formulation, which resulted in improved behavior. However, due to continued myoclonic seizures, GBP was discontinued, with resolution of myoclonic seizures. We found apparent decrease in tolerability (cases 1, 3) and efficacy (case 2) of generic formulations of GBP in our patients, as compared to name brand formulation. Other precipitating factors were not identified, to explain the adverse events noted. The difference may possibly be due to either inert ingredients, or amount of GBP, of these formulations. Therapeutic equivalency between generic and brand name formulations should not be assumed for all patients. Though most do well with transitions, our series describes that decreased efficacy and tolerability may be seen with generic GBP (not previously reported); those who require higher doses for seizure control, or who may be more sensitive to adverse reactions from medications, may be at higher risk for such adverse events as seen in our cases. Adequate vigilance in monitoring efficacy and tolerability is recommended when changing formulations of GBP.