Effects of co-administration of monomethylaminoantipyrine with diethylaminoethyl 2,2-diphenylvalerate (SKF 525-A) on gamma-glutamyltranspeptidase, glutathione S-transferase and hepatic drug metabolizing enzyme activities in rats.

4-Monomethylaminoantipyrine (MAA)-induced increase of hepatic drug metabolizing enzymes was suppressed by SKF 525-A. This may be due to the partial binding of SKF 525-A to a portion of cytochrome P-450. On the other hand, glutathione S-transferase and gamma-glutamyltranspeptidase (gamma-GTP) activities of rat liver were both induced by repeated administration of MAA in combination with SKF 525-A. In addition, under the same condition, glutathione level in rat liver was significantly decreased.