Monitoring of haloperidol serum levels and it's clinical significance

The time course of binding to striatal dopamine D2 receptors by the neuroleptic ziprasidone (CP-88,059-01) determined by positron emission tomography

Positron emission tomography (PET) and 11C-raclopride were used to assess the time course of binding to central dopamine D2 receptors by the novel neuroleptic ziprasidone. In a third party blind study, six healthy male control subjects received a predose of 40 mg ziprasidone and were scanned at an interval of between 4 and 36 h post-dose. One additional subject was assigned to placebo predose and was scanned at 4 h post-dose. Binding potential (BP) was compared with that seen in the subject predosed with placebo and with that seen in nine unmedicated normal volunteers. Subjects studied up to 12 h post-dose had BPs that were greater than 2 SD less than the mean BP, indicative of extensive D2 receptor binding by ziprasidone. With increasing time between dosing and PET scanning there was a curvilinear increase in BP, so that all studies performed at or after 18 h post-dose gave BPs in the normal range (mean +/- 2 SD). Elevated prolactin levels returned to within the normal range by 18 h post-dose. PET measures of binding potential correlated significantly with serum levels of ziprasidone at the time of scanning and less significantly with absolute prolactin levels at the same time.

Is there a relationship between antipsychotic blood levels and their clinical efficacy? An analysis of studies design and methodology

There are now more than 50 studies concerning neuroleptic blood levels and clinical outcome relationships. Haloperidol, the most studied, is the only antipsychotic permitting some conclusions. A number of authors suggest that the striking lack of agreement between different studies results from heterogeneity of their quality. Here, we have used a scoring system for assessing the quality of those studies. According to this system, none (0/14) of the studies having a score < 0.60 was able to show a therapeutic window, as compared to 53% (10/19) of those having a score > or = 0.60 (p = 0.002, Fisher exact test). Also, the studies able to identify the presence of a therapeutic window during haloperidol treatment were those having sample size > 20 (p = 0.06) and those whose patients were treated with fixed doses (p = 0.02). The diagnosis of schizophrenia in the studies seems not to be an exclusive condition, as compared with those also including schizophreniform and schizoaffective disorders (p = 0.12). Our qualitative analysis of haloperidol blood level publications seem to indicate that an upper limit may exist for haloperidol efficacy; values above this limit seem not to provide any supplementary clinical improvement and may even reduce therapeutic effect.

Reduced haloperidol plasma concentration and clinical response in acute exacerbations of schizophrenia

Twenty-nine hospitalized patients suffering acute exacerbations of schizophrenia were treated for 2 weeks with fixed daily oral doses of haloperidol prospectively calculated to achieve a haloperidol plasma concentration of either 8-18 ng/ml or 25-35 ng/ml. Reduced haloperidol as well as haloperidol concentrations were assayed to determine if the former enhanced the predictability of response. Wee 2 haloperidol plasma concentrations were negatively correlated to clinical response as measured by the percentage change in the BPRS score from baseline (r = -0.43, P less than 0.05). In contrast, week 2 plasma concentrations of reduced haloperidol, total haloperidol (haloperidol + reduced haloperidol), and reduced haloperidol/haloperidol ratio did not correlate with the change in the BPRS score. Chi-square analysis concluded that patients with ratios greater than one were no less likely to be treatment responders (less than 25% improvement in BPRS from baseline and week 2 BPRS less than 55) than those with ratios less than one. Although these data lend additional support to reports of a curvilinear relationship between haloperidol plasma concentration and clinical response, they also suggest that reduced haloperidol plasma concentrations are of no value in predicting treatment response.

Clinical response and plasma haloperidol levels in chronic and subchronic schizophrenia

Levels of haloperidol were determined by radioimmunoassay (RIA) in 30 schizophrenic patients (diagnosed according to the criteria of DSM-III), who were treated with fixed doses of this neuroleptic for a period of 21 days. An inverted U-shaped relationship was found between the percent improvement observed in the BPRS global score and the steady state of haloperidol. The interval of effective concentration of haloperidol was set between 12.0 and 35.5 ng/ml. However, the limits of such an interval found in the subchronic schizophrenic subgroup (SS) ranged from 7.4 to 24.9 ng/ml, whereas in the chronic schizophrenic subgroup (CS), it ranged from 14.8 to 38.5 ng/ml. This finding suggests that the interval of effective concentrations may vary as a function of the number of years of evolution of the subjects' illness. This may be compatible with the development of tolerance in the mesolimbic and/or mesocortical dopaminergic systems as a response to prolonged neuroleptic treatments.

Clinical implications of determination of plasma haloperidol levels

The aim of this study was to analyze the clinical utility of monitoring plasma levels, since the utility of monitoring is not yet well established. After a washout period, 30 schizophrenic patients were given fixed doses of haloperidol for 3 weeks. A U-shaped second-grade polynomic relationship (R = 0.69) was found between steady state of haloperidol and percentage improvement in total score on the Brief Psychiatric Rating Scale. The interval of effective concentrations was between 12 and 59 ng/ml. Fourteen of the 15 patients who had a steady state of haloperidol within that therapeutic interval were responders: only 5 out of the 15 patients below the therapeutic interval were responders. None of the 5 patients who had concentrations below 8 ng/ml was a responder. Furthermore, responder patients showed a steady-state level of haloperidol significantly higher than that of nonresponders. These data suggest that plasma levels of haloperidol are predictors of therapeutic response in schizophrenic disorders.

Determination of plasma haloperidol concentrations by radioreceptor assay in schizophrenia: clinical utility

1. Haloperidol concentrations were determined by radioreceptor assay (RRA) and prolactin concentrations were measured in 20 patients diagnosed as schizophrenia (DSM-III). 2. The patients were treated with a fixed dose of haloperidol for 21 days. 3. Our results suggest the existence of a curvilinear relationship, in the form of an inverted U, between stable haloperidol levels and clinical improvement assessed by total BPRS score. 4. We also found a curvilinear relationship between the improvement observed in positive symptoms and state steady levels. 5. No relationship was seen between improvement in negative symptoms and state steady levels. 6. An interval of optimal haloperidol concentration was found: 8.1 ng/ml to 19.6 ng/ml. 7. No relation was found between the dose of haloperidol administered and plasmatic concentration, nor between haloperidol and prolactin levels. 8. Our findings suggest that haloperidol concentrations determined by RRA have clinical utility as predictors of response in schizophrenia.

Neuroleptic plasma concentrations and clinical response: in search of a therapeutic window

There is much interest in finding a therapeutic window for commonly used neuroleptics so that dosage can be individualized and side effects minimized. The authors review specific requirements of good study design and survey the literature that has investigated the relationship between therapeutic response and plasma concentrations of neuroleptics. The evidence from a number of fixed-dose haloperidol studies suggests, but does not yet prove, the existence of a therapeutic window for this compound.

In vivo assay for neuroleptic receptor binding in the striatum. Positron tomography in humans

Using PET, we investigated the potency in six patients of therapeutic doses of neuroleptic drugs for preventing specific binding of trace doses of intravenously administered 76Br-labelled bromospiperone to corpus striatum in vivo. Measured receptor occupancy showed a clear-cut dose-dependent saturation curve with increasing daily oral dose of neuroleptics, indicating the validity and reliability of the method when used as an in vivo radioreceptor assay. Following drug withdrawal in eight patients, recovery to normal or supranormal receptor availability occurred in a matter of days. The results demonstrate an approach that may help resolve controversies about, and design better strategies for, neuroleptic treatment schedules.

Plasma level monitoring of antipsychotic drugs. Clinical utility

The steady-state plasma concentrations of antipsychotic drugs show large interpatient variations but remain relatively stable from day to day in each individual patient. Monitoring of antipsychotic drug concentrations in plasma might be of value provided the patients are treated with only 1 antipsychotic drug. Some studies have reported a relationship between therapeutic response and serum antipsychotic drug 'concentrations' as measured using the radioreceptor assay (RRA) method, which measures dopamine receptor-blocking activity in plasma. Most studies, however, have failed to demonstrate such a relationship, and the RRA does not seem to provide the generally useful tool for plasma concentration monitoring of antipsychotic drugs that was hoped for initially. A lack of correlation between dopamine receptor-blocking activity in plasma and therapeutic response may be due to differences in the blood-brain distribution of both antipsychotic drugs and their active metabolites. Chemical assay methods (e.g. GLC and HPLC) have been used in studies which examined the relationships between therapeutic response and antipsychotic drug concentrations in red blood cells and in plasma. It seems that for these drugs, measuring red blood cell concentrations does not offer any significant advantage over measuring plasma concentrations. Reasonably controlled studies of plasma concentration-response relationships using randomly allocated, fixed dosages of chlorpromazine, fluphenazine, haloperidol, perphenazine, sulpiride, thioridazine and thiothixene have been published but often involve relatively few patients. A correlation between therapeutic response and plasma concentrations of thioridazine and its metabolites has not been demonstrated, and plasma level monitoring of thioridazine and its metabolites therefore appears to have no clinical value. Clinical behavioural deterioration concomitant with high plasma concentrations of chlorpromazine and haloperidol have been reported. A dosage reduction might be considered after 2 to 4 weeks' treatment in non-responders who have plasma chlorpromazine concentrations above 100 to 150 micrograms/L or plasma haloperidol concentrations above 20 to 30 micrograms/L. Non-responders and good responders to chlorpromazine treatment, however, have plasma drug concentrations in the same range, and a therapeutic range of plasma chlorpromazine levels has not been defined. Therapeutic plasma haloperidol concentrations (i.e. 'window') in the range of 5 to 20 micrograms/L have been reported by some investigators, but others have found no such relationship.(ABSTRACT TRUNCATED AT 400 WORDS)