The search continues for a safe, accurate and reliable method to quantify liver function similar in principle to renal creatinine clearance or pulmonary function spirometry tests. When evaluating patients in the more advanced stages of chronic liver disease, one’s clinical judgement regarding the degree of liver dysfunction usually suffices, but in patients with early or only intermediate disease, an estimate based on routine blood tests and/or clinical severity scores is often unreliable. A more quantitative approach under investigation at present has been to monitor specific pharmacokinetic parameters of ‘probe’ drugs metabolized primarily by hepatic cytochrome P-450. These parameters include the plasma or salivary clearance rate of the parent compound and/or the formation rate of its metabolites. Following a review of basic hepatic pharmacology relevant to this topic, we shall explore the advantages and disadvantages of two ‘metabolic probes’ that have shown the most promise to date, caffeine and lidocaine.

The quantitative measurement of liver function is difficult and imprecise because of dissociation of the various metabolic functions of the liver and is subject to error because of interindividual variability in substrate metabolism. Any attempt to develop new, easy-to-repeat, quantitative tests is nonetheless worthwhile, because liver function has prognostic implications. Previous attempts to propose candidate liver function tests for diagnostic purposes6 have not been followed by their use in clinical practice, and the statement that MEG-X production may "reduce the need for repeated histology examinations" is not likely to be validated by future works.

No abstract

No abstract