The kinetics of idebenone (45 mg twice daily p.o.) in 6 Caucasian chronic hepatopathic patients without portal hypertension were studied. The pharmacokinetic parameters were evaluated both for single (day 1) and multiple (day 10) administrations. These 6 patients showed a first order bi-compartimental kinetic curve for idebenone and for its metabolites, superimposable on the curves obtained from healthy volunteers. The C(max) parameters, tmax and bioavailability confirm the absence of accumulation. On day 12, 48 h after the last administration (performed on day 10), there was no evidence of residual drug. One of these patients was being treated with diuretics (chlorthalidone) and with perfusion fluids, including 5% glucose, and no interference was shown between the two drugs. There is no evidence of any particular side effect or alteration of the haematochemical parameters that could be thought to be drug related. This study confirms that idebenone at the dose of 90 mg/day p.o. administered to hepatopathic patients does not cause accumulation or toxicity.