Gamma-glutamyl transpeptidase alterations in liver and serum induced by haloperidol

Changes in the activity of the microsomal enzyme gamma-glutamyl transpeptidase (GGT) were examined in liver and serum following subacute and chronic haloperidol administration to rats. Haloperidol increased both serum and liver GGT levels. The enzymatic activity returned to baseline values on the sixth day after withdrawal of the drug. It is concluded that alterations in serum GGT levels may be expected during prolonged treatment of haloperidol, and that these alterations reflect enzyme induction in liver microsomes where the drug is entirely metabolized.