Dopamine turnover in schizophrenia before and after haloperidol withdrawal. CSF, plasma, and urine studies

The dopamine hypotheses of schizophrenia and antipsychotic drug action suggest that the dopamine metabolite homovanillic acid (HVA) should change with drug withdrawal and change in clinical state. We designed a study of cerebrospinal fluid (CSF), plasma, and urinary HVA on and off haloperidol to examine the effects of drug withdrawal. CSF and plasma HVA samples were obtained in 72 healthy schizophrenic (DSM-III-R) males (age: 36 +/- 7.4 years), before and after haloperidol withdrawal, which was after 6 weeks on placebo or sooner if they met specific criteria for relapse. We collected three 24-hour urine samples in 34 of these patients. In addition, CSF HVA was obtained in 24 well-screened age-matched male normal controls. HVA was measured with high-pressure liquid chromatography (HPLC). CSF HVA decreased significantly after drug withdrawal, particularly in those who met relapse criteria; drug-free CSF HVA levels were not significantly different from those of normals. Plasma HVA increased significantly after haloperidol withdrawal in relapsing patients, but not in clinically stable patients. Urinary HVA excretion decreased after withdrawal with decreased HVA clearance. We conclude that haloperidol withdrawal had a strong effect on dopamine turnover, whereas the patient's clinical state had only a weak central effect, without affecting total body production of HVA. Conceivably, dopamine involvement in schizophrenia reflects the failure of the homeostatic mechanisms that allow for integration of different functional brain components as needed.