A STUDY OF THE POTENTIAL CONFOUNDING EFFECTS OF DIET, CAFFEINE, NICOTINE AND LORAZEPAM ON THE STABILITY OF PLASMA AND URINARY HOMOVANILLIC-ACID LEVELS IN PATIENTS WITH SCHIZOPHRENIA

Ten men inpatients who met DSM-III-R criteria for schizophrenia partic ipated. On five occasions at least one week apart, each subject had an intravenous line placed at 0730 after an overnight fast. On each occa sion blood samples were drawn at 0800 and hourly thereafter through 12 00 noon far measurement of plasma homovanillic acid (HVA). Total four- hour urine collections were obtained for measurement of urinary HVA. S ubjects received five experimental conditions, in randomized sequence: no intervention, smoking one cigarette per hour drinking one caffeina ted cola per hour, lorazepam 2 mg IV push, or a high monoamine meal. B aseline (0800) plasma HVA measures showed only minor intrinsic variabi lity. The average standard deviation in baseline plasma HVA over five occasions of measurement was low relative to the changes in HVA produc ed during treatment with antipsychotic medications. The high monoamine meal significantly elevated plasma HVA, with a similar trend for urin ary HVA. Neither caffeine, nicotine, nor lorazepam significantly affec ted plasma or urinary HVA. (C) 1996 Society of Biological Psychiatry