[Biological tests as indirect indicators of the activity of drug metabolizing enzymes. Use of glucaric acid and gamma-glutamyltransferase].

Laboratory tests are increasingly important in the surveillance of drug treatments. People in charge of clinical laboratory science must now become aware of a new development, the use of as indicators of the activity of drug-metabolizing enzymes, especially of the induction of such enzymes. Ideally, the activity of such enzymes should be measured in the tissues. In man, however, easier indirect methods of application are now most often used : measurement of antipyrine half-life, urinary and plasma drug metabolites, protein and specific enzyme levels in palsma, changes in endogenous substrates and endogenous metabolites, and enzymes in circulating blood cells. Of all these, two examinations are now widely performed, those for urinary glucaric acid and gamma-glutamyltrasferase. The value and limitations of these two tests are discussed.