TARDIVE-DYSKINESIA EXACERBATED AFTER INGESTION OF PHENYLALANINE BY SCHIZOPHRENIC-PATIENTS

Despite continued research, the influences that promote or exacerbate tardive dyskinesia (TD) symptoms remain incompletely understood. Recen t findings (Gardos et al. 1992; Richardson et al. 1989) suggest that i ngestion of the dietary constituent, phenylalanine, might exacerbate T D symptoms, but a double-blind, placebo-controlled challenge had not p reviously been conducted in schizophrenic patients. On two different m ornings, in counterbalanced order, 18 male schizophrenic patients with TD were challenged with either 100 mg/kg phenylalanine or placebo. ph enylalanine were measured 90 minutes post-challenge. The results suppo rted ted the hypothesis in that involuntary movements increased to a s tatistically and clinically meaningful degree after the phenylalanine challenge, but not after placebo. No effects on memory were detected. Significant order effects characterized the plasma findings but lot th e behavioral data. Results indicate that a dietary constituent, the am ino acid phenylalanine, can potentially exacerbate tardive dyskinesia symptoms in schizophrenic patients. The influence of phenylalanine and other ingested substances on clinical symptomatology warrants further investigation. (C) 1997 American College of Neuropsychopharmacology [ Neuropsychopharmacology 16:136-146, 1997]