Generic substitution of anti-epileptic drugs is generally not advised by neurologists. The present study investigated the switchability of gabapentin 800mg tablets (NEURONTIN® and GABASANDOZ® ) using an individual bioequivalence (IBE) study design with 2 batches of each product, and assessed whether between-batch and between-formulation variability in exposure play a significant role in the within-subject variability. The trial was analysed according to the Food and Drug Administration framework to establish IBE. IBE was shown between both products with the 95% upper confidence bound (UCB) of the IBE criterion being -2.01 and -2.31 for AUC0-inf and Cmax , respectively. Subject-by-formulation variability (1.35%) was negligible compared to the within-subject variability of AUC0-inf with NEURONTIN® (19.0%) and GABASANDOZ® (23.6%). Inclusion of an additional batch didn't significantly change this within-subject variability (20.2% and 23.6%, respectively). This study shows that substitution of gabapentin 800mg tablets of NEURONTIN® and GABASANDOZ® should be possible without affecting clinical outcomes. This article is protected by copyright. All rights reserved.