The kinetics of Ru(III) catalysed oxidation of neuroleptic drug, gabapentin by diperiodatonickelate(IV) (DPN) in alkaline medium at 298 K and a constant ionic strength of 0.30 mol dm(-3) was studied spectrophotometrically. The oxidation products are 1-(hydroxymethyl) cyclohexane acetic acid and Ni(II) which are identified by spectral studies. The stoichiometry of the reaction is 1:1 which is similar as in the case of absence of ruthenium(III). The oxidation reaction in alkaline medium has been shown to proceed via a Ru(III)-gabapentin complex, which further reacts with deprotonated form of DPN in a rate determining step, which is followed by other fast steps to give the products. The reaction constants involved in the different steps of the mechanism are calculated. The activation parameters with respect to slow step of the mechanism are computed and discussed and thermodynamic quantities are also determined. The catalytic constant (K-c) was calculated at different temperatures. The probable active species of catalyst and oxidant have been identified. (c) 2007 Elsevier B.V. All rights reserved.