Gabapentin and carbamazepine affect eye movements and posture control differently: A placebo-controlled investigation of acute CNS side effects in healthy volunteers

Abstract 

This prospective study examined the effects of the new antiepileptic drug (AED) gabapentin (GBP) compared to the standard AED carbamazepine (CBZ) and placebo (PLA) on eye movements, posture and finger force control in 12 healthy volunteers who received single doses of 600 mg GBP and 400 mg CBZ in a placebo-controlled, double-blind, cross-over, randomized trial. CBZ and GBP reduced almost equally (8% vs. 10%) the mean peak saccade velocity as compared to PLA (P<0.05). CBZ, but not GBP, significantly prolonged the duration of saccades as compared to placebo (14–24%) (P<0.05). GBP produced a greater maximal increase of body sway than CBZ with eyes open (P<0.01) and eyes closed (P<0.001). CBZ and GBP did not significantly influence control of grip force. CBZ effects were better correlated with plasma levels. Subjective side effects were more pronounced with CBZ than GBP. Although CBZ and GBP cause similar CNS side effects, the effects on eye movements and body sway were different. CBZ predominantly affects saccadic eye movements, whereas GBP had more impact on posture control. Thus, electro-oculography seems to be more appropriate in the detection of CBZ-induced side effects and posturography appears to be more sensitive in the detection of side effects associated with GBP.

Keywords:  Gabapentin, Carbamazepine, Side effects, Posturography, Electro-oculography