Relationship of antiepileptic drugs to generic brittleness in patients with epilepsy

The purpose of the study was to assess if any antiepileptic drug (AED) was associated with patients being generic brittle (GB) and if any specific AED caused - and was not merely associated with - more frequent switch problems.

Chi square and binary logistical regression analysis were performed, using a previously described study in patients with epilepsy who were routinely followed at the University of Maryland epilepsy outpatient clinic in Baltimore, Maryland. Determination of generic brittleness mirrored clinical practice and included patient opinion about generic formulations, usually based on a history of worsened seizures or side effects with prior AED formulation switching. The dataset included a total of 148 patients, who took 30 different AED formulations. Patients collectively took 530 AED formulation products.

Taking lamotrigine immediate release (IR) tablets was associated with a greater probability of being GB and tended to cause more frequent switch problems. Interestingly, six AEDs - Vimpat tablet, carbamazepine IR tablet, phenobarbital (any formulation), gabapentin capsule, Lyrica capsules, and phenytoin (any formulation) - were associated with a reduced probability of being GB, although perhaps not through greater efficacy and tolerability, or better formulation quality. Since tablet and capsule appearance may influence patient perceptions and clinical outcomes, it was observed that the six AEDs less associated with being GB also tended to have fewer generics, and hence possibly lessen treatment uncertainties from the patient perspective. A patient taking more AEDs had significantly increased odds of having a switch problem. An additional observation was that, when a generic was available for their most problematic AED, GB patients took a generic AED only 50% of the time, while not GB patients took a generic AED all the time.

Taking lamotrigine IR tablets was associated with a greater probability of being GB and tended to cause more frequent switch problems than other AEDs in this cohort of patients. Six AEDs were associated with a reduced probability of being GB. The lower number of different generics for these six drugs may result in greater patient certainty in medication identity, due to greater consistency in medication color, shape, and size, and hence less generic skepticism or generic brittleness. Also, patients taking more AEDs showed increased odds of a switch problem.