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The pharmacokinetic parameters of lidocaine are pertinent to the determination of both appropriate loading doses and constant infusion rates that achieve a therapeutic plasma concentration while avoiding toxicity. Because lidocaine is used primarily in older patients who may have concurrent diseases, the effects of disease states on lidocaine disposition are important when calculating lidocaine doses. Patients with congestive heart failure and hepatic disease have pronounced changes in lidocaine clearance. Patients placed on prolonged lidocaine infusions have a change in disposition half-life of the drug. Patients with renal disease do not have significant alterations in handling the parent compound but, because of the dependence of glycinexylidide elimination on renal function, may accumulate the metabolite and develop central nervous system toxicity. Even though there are differences in some of the pharmacokinetic variables for lidocaine in young and elderly patients, the clearance of the drug was not significantly different in the two patient groups. The effects of concurrently administered drugs on lidocaine pharmacokinetics remain to be more widely studied in patients.