Measuring lidocaine metabolite--monoethylglycinexylidide as a quantitative index of hepatic function in adults with chronic hepatitis and cirrhosis

Lidocaine is metabolized to form monoethylglycinexylidide (MEGX) via oxidative N-deethylation in the liver. To assess the clinical value of this lidocaine metabolite as a quantitative liver function test, we measured the serum MEGX concentration 15 min after intravenous administration of a single dose of lidocaine (1 mg/kg) in 24 adults with chronic hepatitis, 47 patients with cirrhosis and 26 normal controls. A fluorescence polarization immunoassay was used to obtain the MEGX value. The MEGX concentration in controls was 67 (54-95) ng/ml (median with 16th-84th percentile in parentheses), which was higher than 43 (23-61) ng/ml in patients with chronic hepatitis and 24 (7-52) ng/ml in those with cirrhosis (P < 0.05). In addition, the serum MEGX levels are proportional to the galactose elimination capacity, and inversely proportional to Pugh's score, the prothrombin time and indocyanine green retention ratio. If a MEGX concentration of below 54 ng/ml is taken as an indicator of hepatic dysfunction, its diagnostic sensitivity for hepatic disorder is 84.5%, specificity 88.5% and accuracy 85.6%. Furthermore, after a 10-month follow-up, patients with MEGX formation above 30 ng/ml had a higher survival rate than those with a MEGX concentration below this level (P = 0.004). In conclusion, the MEGX formation test reflects the severity of hepatic dysfunction quite well, making it valuable both in the quantitative evaluation of liver function and in the prognostic prediction of adults with liver diseases.