Preliminary comparative analysis of kynurenine pathway metabolites in chronic ketamine users, schizophrenic patients, and healthy controls

OBJECTIVE The serum kynurenine pathway metabolites kynurenic acid (KYNA), kynurenine (KYN), and tryptophan (TRP) were examined in chronic ketamine users and in schizophrenic patients. The correlations of the metabolites with sociodemographic data, clinical characteristics, and drug use status were analyzed. METHODS Seventy-nine healthy controls, 78 ketamine users, and 80 schizophrenic patients were recruited. Serum TRP, KYN, and KYNA levels were measured by high-performance liquid chromatography following tandem mass spectrometry (MS/MS). Psychotic symptoms were evaluated using the positive and negative syndrome scale (PANSS), the Beck Depression Inventory (BDI), and the Beck Anxiety Inventory (BAI). RESULTS Serum levels of TRP, KYNA, and KYN (in ketamine users only) were lower in ketamine users and schizophrenic patients than in controls (p