Comparative study of effects of gabapentin, vigabatrin and sodium valproate on psychomotor performance in healthy volunteers

Abstract

Context: The cognitive and psychomotor functions may become impaired in epileptic patients due to underlying etiology, effect of seizures and side-effects of antiepileptic drugs. It is desirable for the drug to have a minimal effect on cognitive abilities. Few studies have evaluated the psychomotor effects of newer antiepileptic agents and hence do not have the proper evidence base for their psychomotor adverse effects. Aims: The aim of this study is to evaluate the effects of gabapentin (GBP), vigabatrin (VGB), valproate (VAL) on psychomotor functions. Settings and Design: Randomized, prospective, double-blind, placebo (PLB) controlled crossover study. Subjects and Methods: A total of 24 healthy volunteers were included to administer single oral doses of GBP 300 mg, VGB 500 mg, sodium valproate 200 mg and PLB following a Latin square design. The objective parameters - six-digit cancellation test, digit symbol substitution test, critical flicker fusion test, arithmetic ability test, digit span test, hand steadiness test and subjective parameters like visual analog scale (VAS) were tested at 0, 1, 2 and 3 h. Statistical Analysis Used: Repeated measures ANOVA was used to compare the difference in mean score. Fisher's exact test was used for statistical analysis of adverse effects. Results: Sodium valproate impaired all subjective and objective psychomotor functions while GBP, VGB did not show any impairment when compared with PLB. GBP when compared with VGB, no difference was observed in any test, but when both the drugs were compared with sodium valproate, statistically significant difference at the end of third hourwas observed. Conclusions: VGB and GBP have few adverse cognitive and psychomotor effects as compared with sodium valproate, therefore are safe as add on therapy or monotherapy.