(CO2)-C-13 excretion in breath of normal subjects and cirrhotic patients after C-13-aminopyrine oral load. Comparison with MEGX test in functional differentiation between chronic hepatitis and liver cirrhosis

BACKGROUND/AIMS: Liver function can be evaluated using C-13 breath tests th at explore liver Cytochrome P-450 activity. Aminopyrine is one of the first compounds used in liver function testing. Lidocaine metabolism to monoethy lglycinexylidide is also a valid tool to assess liver function. Although li ver Cytochrome P-450 metabolizes both compounds, lidocaine metabolism is fl ow-dependent while aminopyrine metabolism does not depend on liver blood fl ow. METHODOLOGY: The Ist part of the study evaluated the appearance and disappe arance rate of (CO2)-C-13 in the breath of both normal subjects and in cirr hotic patients, so as to establish optimal sampling times and to evaluate t he amount of time needed before performing a subsequent breath test. The 2n d part of the study compared the aminopyrine breath test with the monoethyl glycinexylidide test in patients with chronic hepatitis or cirrhosis. RESULTS: Complete (CO2)-C-13 disappearance was recorded 24 hours after the test in normal subjects, while it took 3 days to disappear from the breath of cirrhotic patients. Breath sampling at 60, 120 and 180min were equally v alid in differentiating chronic hepatitis from cirrhosis. The aminopyrine b reath test and monoethylglycinexylidide test showed a good yet not close co rrelation. CONCLUSIONS: This study showed that in cirrhotic patients a C-13 breath tes t can be performed 3 days after the previous one. In chronic hepatitis and cirrhotic patients, the aminopyrine breath test and the monoethylglycinexyl idide test evaluated similar, but not identical, hepatic subfunctions, sugg esting that multiple C-13 breath test using different substrates could expl ore liver function better.