Pharmacokinetics of lidocaine and its metabolite as a hepatic function marker in dogs

Measuring hepatic metabolic function is critical for detection and treatment of liver failure. Several tests have been widely used to characterize the integrity of liver; however, they do not evaluate the metabolic function of the organ, most requiring multiple blood draws. The purpose of this study was to establish if the ratio of the lidocaine metabolite monoethylglycinexylidide (MEGX) divided by lidocaine concentration at 30 min post intravenous lidocaine administration is a good marker of metabolic activity of the liver. Nine healthy and two partially hepatectomized and auto-transplanted dogs were included in the study. A single 1.5 mg/kg intravenous dose of lidocaine and serum samples were obtained at selected times for 150 minutes. Serum concentrations of lidocaine and MEGX were determined by a validated high-performance liquid chromatographic method. Pharmacokinetic parameters were obtained by non-compartmental methods and ratio of AUC of MEGX divided by AUC of lidocaine was determined for each dog. This ratio was correlated with the ratio of the concentration of the compounds obtained 30 minutes after drug administration. A good concordance was obtained, suggesting that ratio obtained with a single sample may be useful to predict the hepatic metabolism function. To validate the test, dogs hepatectomized and auto-transplanted were plotted and the results obtained were within the values obtained in healthy dogs. These results suggest that ratio of MEGX/lidocaine obtained 30 min after administration could be a good marker of hepatic metabolic function.