Brief debrisoquin administration to assess central dopaminergic function in children

Plasma homovanillic acid in neuroleptic responsive and nonresponsive schizophrenics

Changes in plasma homovanillic acid (HVA) were investigated in neuroleptic responsive and nonresponsive schizophrenics in order to delineate parameters of dopamine regulation, which may underlie differences in neuroleptic responsivity. Nineteen schizophrenics were treated with haloperidol for 6 weeks. HVA was sampled at baseline, 24 hr after initial neuroleptic dose, and after 6 weeks of treatment. Subjects were pretreated with debrisoquin in order to reduce the peripheral production of HVA. The responders had an initial rise in HVA at 24 hr after first neuroleptic dose, followed by a decline back to baseline over the 6 weeks of treatment. The nonresponders' HVA failed to rise at 24 hr after first neuroleptic dose. At 6 weeks of treatment their HVA had fallen to significantly below baseline. Thus, a rise in HVA 24 hr after the first dose of neuroleptic predicted treatment response; a fall in HVA at 6 weeks to below pretreatment values was associated with neuroleptic nonresponse.

Morning variations of plasma homovanillic acid in untreated schizophrenic patients

Plasma concentrations of homovanillic acid were determined in samples obtained at 8.30 a.m. and 12.30 p.m. from 29 untreated schizophrenic patients, 14 males and 15 females. When the earlier samples were compared with the later, a significant decrease in mean plasma homovanillic acid level was observed, but only in the male patients. The morning fall was observed in 10 of 14 male patients and 6 of the 15 female patients. This morning rhythm in plasma homovanillic acid concentration may mask the putative rises in plasma homovanillic acid provoked by neuroleptic administration and may explain some of the observed differences between findings in studies involving the assessment of this metabolite.

Clinical ratings and plasma HVA during cocaine abstinence

Six patients were evaluated over a 21-day period during inpatient recovery from chronic repeated cocaine use. Serial evaluations of Hamilton depression rating, cocaine craving, plasma homovanillic acid (pHVA), and plasma 3-methoxy-4-hydroxyphenylethyleneglycol (pMHPG) concentrations were determined. There was a distinct increase in cocaine craving between 1 and 2 weeks after the last cocaine use. Levels of pHVA also increased at the time of heightened craving. The data provide preliminary evidence to suggest that changes in cocaine craving during abstinence are positively correlated with changes in dopamine turnover.

Pharmacodynamics and pharmacokinetics of haloperidol and reduced haloperidol in schizophrenic patients

Twelve male chronic schizophrenic inpatients, neuroleptic-free for at least 4 weeks, were given an oral test dose of 10 mg haloperidol (HAL) and reduced HAL (RHAL) in a random order, with a 2-week interval. Two weeks after the last test dose, the patients were given HAL, 5 mg orally twice daily for 7 days. Blood samples were drawn at baseline and between 0.5 and 24 hr after the test doses, and during HAL treatment as well. Plasma drug concentrations and homovanillic acid (HVA) levels were measured with high-performance liquid chromatography using electrochemical detection. HAL, but not RHAL, produced increments in plasma HVA (pHVA) levels at 24 hr after a test dose. pHVA levels remained higher than baseline during HAL treatment. Detectable interconversion between HAL and RHAL was observed in eight patients. The capacity of the reductive drug-metabolizing enzyme system, however, was greater than that of the oxidative processes. The plasma RHAL:HAL ratios on days 6 and 7 were higher than and positively correlated with those at Tmax after a single dose of HAL and were negatively correlated with the HAL:RHAL ratios at Tmax after a single dose of RHAL. Thus, both reductive and oxidative drug-metabolizing systems probably contribute to individual differences in plasma RHAL:HAL ratios in HAL-treated schizophrenic patients.

Reproducibility of the measurement of plasma noradrenergic and dopaminergic metabolites in normal subjects

The object of this study was to determine the reproducibility of the measurement of plasma catecholamine metabolites in normal control subjects and to assess the influence of factors such as time of day, diet, activity, blood pressure, and mood on the variance of these measures. Plasma free homovanillic acid (HVA), 3-methoxy-4-hydroxyphenylglycol (MHPG), and vanillylmandelic acid (VMA) were simultaneously measured by high performance liquid chromatography with electrochemical detection. Samples were collected from 15 doctors and nurses at 8 a.m. and at noon on 2 separate days. After the fasting 8 a.m. sample, the subjects ate a regular hospital breakfast. Activity in their usual tasks on an inpatient psychiatric unit was monitored electronically by an activity meter. Levels of each metabolite were not significantly different between days at the respective assay times and were highly correlated for individuals. MHPG showed a significant increase from morning to noon, while HVA showed a significant decrease. Activity, dietary intake of tyrosine and tyramine, blood pressure, pulse, scores on the Profile of Mood States, age, and sex were not related to plasma levels. The results demonstrate that measures of dopamine and norepinephrine metabolites have significant reliability in normal subjects in a setting used for research studies with psychiatric patients.

Plasma-free homovanillic acid: within- and across-day stability in children and adults with Tourette's syndrome

Within- and across-day stability of plasma-free homovanillic acid (pHVA) was assessed in children and adults with Tourette's syndrome. A diurnal fall in pHVA was observed in 13 of 15 subjects. There was a small but significant (p less than .0001) decrease (8%) in mean morning pHVA levels obtained just 20 minutes apart (8:30 A.M. and 8:50 A.M.). A substantial and significant (p less than .001) mean decrease in pHVA (25%) was observed when samples obtained between 8:00 and 8:30 A.M. were compared with samples obtained at 12:00 noon. Changes in pHVA levels observed during the afternoon (between 12:00 noon and 4:00 P.M.) were small, nondirectional, and nonsignificant. Repeated measurement of morning pHVA in the same individual after 24 or more hours revealed marked increases or decreases in many individuals, suggesting that morning pHVA is not a stable measure. The results of this and previous studies suggest that pHVA obtained at 12:00 noon or later in the day may be a more reliable measure of centrally produced HVA. Further studies are needed regarding the stability of pHVA over time.