FORMATION KINETICS OF THE LIDOCAINE METABOLITE (MEGX) IN PATIENTS WITH CHRONIC ACTIVE HEPATITIS AND CIRRHOSIS

Objective: To evaluate the formation kinetics of monoethylglycinexylid ide (MEGX), the principal lidocaine metabolite, in patients with chron ic active hepatitis or cirrhosis. Design: The study was designed in or der to identify the best timing of MEGX determination and to compare M EGX formation with indocyanine green (ICG), galactose and chenodeoxych olic acid clearances. Methods: Fifty subjects were studied: six health y individuals, 22 patients with chronic active hepatitis and 22 patien ts with cirrhosis. Serum MEGX concentrations were evaluated 15 min aft er i.v. lidocaine administration (i mg/kg) and every 30 min for 180 mi n. MEGX formation was related to lidocaine kinetic and quantitative li ver tests. MEGX determination was carried out by fluorescence polariza tion immunoassay on the TDX system. Results: Determination of MEGX con centrations could differentiate between chronic active hepatitis and c irrhosis (P < 0.01). Blood samples taken at 30 min (MEGX30) after lido caine administration showed the higher relationships both with fractio nal formation half-life (r = -0.508, P < 0.001) and hourly area under the curve (r = 0.995, P < 0.001) of this metabolite. In multivariate a nalysis, MEGX30 showed significant correlation with lidocaine eliminat ion rate half-life (P = 0.0097), chenodeoxycholic acid (P = 0.0001) an d ICG (P = 0.039) clearances. Discriminant MEGX30 cut-off values betwe en chronic active hepatitis and cirrhosis, showed four functional leve ls: normal (> 72 ng/ml), mild (72-50 ng/ml), moderate (49-18 ng/ml) an d severe (< 18 ng/ml) functional impairment, according to progressive degrees of liver damage. Conclusion: Determination of MEGX concentrati ons at 30 min after lidocaine infusion seems a suitable 'one-sample' d ynamic liver function test. MEGX determination could be a useful test to check the evolution of the chronic active hepatitis in addition to cirrhosis.