The influence of sulfonamides on the estimation of γ-glutamyltranspeptidase activity

The possibility of misinterpreting results of the determination of γ-glutamyl transpeptidase (GGTP) activity in serum due to the influence of sulfonamides on the colour reaction or the enzymic reaction itself was assayed. Five sulfonamide drugs were tested in vitro and in 46 patients. GGTP activity was estimated by four methods. The results of the naphthylamide method were influenced (in the sense of some increase of the values) by the sulfonamides with antibacterial effect, by way of interference of these sulfonamides with the Bratton and Marshall procedure used in this method. The values obtained with the naphthylamide-glycylglycine method were not influenced by any sulfonamides. By two methods, using γ- l -glutamyl -p- nitroanilide , it was found that at a therapeutic sulfonamide concentration in blood, no inhibition of serum GGTP activity was observed.