Original Article

Neuropsychopharmacology (1997) 16 136–146. doi:10.1016/S0893-133X(96)00054-1

Tardive Dyskinesia Exacerbated after Ingestion of Phenylalanine by Schizophrenic Patients

Diane M Mosnik MS1,2, Bonnie Spring Ph.D2,3, Keith Rogers MD, Ph.D4 and Sankar Baruah MS1

  1. 1From the Department of Psychiatry, University of Iowa College of Medicine, Iowa City, Iowa
  2. 2Department of Psychology, Finch University of Health Sciences/Chicago Medical Schook, Chicago, Illinois
  3. 3Biological Psychiatry, Hines Veterans Affairs Medical Center, North Hines Illinois
  4. 4Psychiatry Service, Seattle Veterans Affairs Medical Center, Seattle, Washington

Correspondence: Diane M Mosnik, The University of Iowa Hospitals and Clinics, MHCRC Rm 2911JPP, Department of Psychiatry, 200 Hawkins Drive, Iowa City, IA 52242

Received 11 September 1995; Revised 24 January 1996; Accepted 26 January 1996



Despite continued research, the influences that promote or exacerbate tardive dyskinesia (TD) symptoms remain incompletely understood. Recent findings (Gardos et al. 1992; Richardson et al. 1989) suggest that ingestion of the dietary constituent, phenylalanine, might exacerbate TD symptoms, but a double-blind, placebo-controlled challenge had not previously been conducted in schizophrenic patients. On two different mornings, in counterbalanced order, 18 male schizophrenic patients with TD were challenged with either 100 mg/kg phenylalanine or placebo. Effects on abnormal involuntary movements, recall memory, and plasma phenylalanine were measured 90 minutes post-challenge. The results supported the hypothesis in that involuntary movements increased to a statistically 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 not the behavioral data. Results indicate that a dietary constituent, the amino 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.


Tardive dyskinesia; Schizophrenia; Phenylalanine; Amino acids

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