Haloperidol and lorazepam combined: clinical effects and drug plasma levels in the treatment of acute schizophrenic psychosis

Automated Interlaboratory Comparison of Therapeutic Drug Monitoring Data and Its Use for Evaluation of Published Therapeutic Reference Ranges

Therapeutic drug monitoring is a tool for optimising the pharmacological treatment of diseases where the therapeutic effect is difficult to measure or monitor. Therapeutic reference ranges and dose-effect relation are the main requirements for this drug titration tool. Defining and updating therapeutic reference ranges are difficult, and there is no standardised method for the calculation and clinical qualification of these. The study presents a basic model for validating and selecting routine laboratory data. The programmed algorithm was applied on data sets of antidepressants and antipsychotics from three public hospitals in Denmark. Therapeutic analytical ranges were compared with the published therapeutic reference ranges by the Arbeitsgemeinschaft für Neuropsychopharmakologie und Pharmakopsychiatrie (AGNP) and in additional literature. For most of the drugs, the calculated therapeutic analytical ranges showed good concordance between the laboratories and to published therapeutic reference ranges. The exceptions were flupentixol, haloperidol, paroxetine, perphenazine, and venlafaxine + o-desmethyl-venlafaxine (total plasma concentration), where the range was considerably higher for the laboratory data, while the calculated range of desipramine, sertraline, ziprasidone, and zuclopenthixol was considerably lower. In most cases, we identified additional literature supporting our data, highlighting the need of a critical re-examination of current therapeutic reference ranges in Denmark. An automated approach can aid in the evaluation of current and future therapeutic reference ranges by providing additional information based on big data from multiple laboratories.

Pharmacokinetic drug interactions with oral haloperidol in adults: dose correction factors from a combined weighted analysis

INTRODUCTION

Pharmacokinetic (PK) drug-drug interactions (DDIs) of oral haloperidol, a first-generation antipsychotic, are systematically reviewed.

AREAS COVERED

After exclusions, the search for DDIs with oral haloperidol provided 47 articles as victim and 7 as perpetrator. Changes in mean haloperidol concentration-to-dose (C/D) ratios after weighting each study's size were used to calculate the effects of other drugs (inhibitors/inducers) on haloperidol. These changes of haloperidol C/D ratio were used to estimate dose-correction factors (<1 for inhibitors and >1 for inducers).

EXPERT OPINION

A box summarizes our recommendations for clinicians regarding our current knowledge of haloperidol PK DDIs, which will need to be updated as new information becomes available. Moderate to strong inducers (carbamazepine, phenobarbital, phenytoin, or rifampin) should be avoided since they required dose-correction factors of 2-5. Smoking appeared to be a weak inducer (dose-correction factor 1.2). Fluvoxamine, promethazine, and combinations of CYP3A4 and CYP2D6 inhibitors should be avoided. There are no long-term studies on fluoxetine to provide a dose correction factor. Limited information suggests that valproate may be an inhibitor (dose-correction factor 0.6). In most patients, haloperidol may not have clinically relevant effects as a perpetrator, but in vitro and clinical studies suggest it is a weak CYP2D6 inhibitor.

Benzodiazepines for psychosis-induced aggression or agitation

BACKGROUND

Acute psychotic illness, especially when associated with agitated or violent behaviour, can require urgent pharmacological tranquillisation or sedation. In several countries, clinicians often use benzodiazepines (either alone or in combination with antipsychotics) for this outcome.

OBJECTIVES

To examine whether benzodiazepines, alone or in combination with other pharmacological agents, is an effective treatment for psychosis-induced aggression or agitation when compared with placebo, other pharmacological agents (alone or in combination) or non-pharmacological approaches.

SEARCH METHODS

We searched the Cochrane Schizophrenia Group's register (January 2012, 20 August 2015 and 3 August 2016), inspected reference lists of included and excluded studies, and contacted authors of relevant studies.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) comparing benzodiazepines alone or in combination with any antipsychotics, versus antipsychotics alone or in combination with any other antipsychotics, benzodiazepines or antihistamines, for people who were aggressive or agitated due to psychosis.

DATA COLLECTION AND ANALYSIS

We reliably selected studies, quality assessed them and extracted data. For binary outcomes, we calculated standard estimates of risk ratio (RR) and their 95% confidence intervals (CI) using a fixed-effect model. For continuous outcomes, we calculated the mean difference (MD) between groups. If there was heterogeneity, this was explored using a random-effects model. We assessed risk of bias and created a 'Summary of findings' table using GRADE.

MAIN RESULTS

Twenty trials including 695 participants are now included in the review. The trials compared benzodiazepines or benzodiazepines plus an antipsychotic with placebo, antipsychotics, antihistamines, or a combination of these. The quality of evidence for the main outcomes was low or very low due to very small sample size of included studies and serious risk of bias (randomisation, allocation concealment and blinding were not well conducted in the included trials, 30% of trials (six out of 20) were supported by pharmaceutical institutes). There was no clear effect for most outcomes.Benzodiazepines versus placeboOne trial compared benzodiazepines with placebo. There was no difference in the number of participants sedated at 24 hours (very low quality evidence). However, for the outcome of global state, clearly more people receiving placebo showed no improvement in the medium term (one to 48 hours) (n = 102, 1 RCT, RR 0.62, 95% CI 0.40 to 0.97, very low quality evidence). Benzodiazepines versus antipsychoticsWhen compared with haloperidol, there was no observed effect for benzodiazepines for sedation by 16 hours (n = 434, 8 RCTs, RR 1.13, 95% CI 0.83 to 1.54, low quality evidence). There was no difference in the number of participants who had not improved in the medium term (n = 188, 5 RCTs, RR 0.89, 95% CI 0.71 to 1.11, low quality evidence). However, one small study found fewer participants improved when receiving benzodiazepines compared with olanzapine (n = 150, 1 RCT, RR 1.84, 95% CI 1.06 to 3.18, very low quality evidence). People receiving benzodiazepines were less likely to experience extrapyramidal effects in the medium term compared to people receiving haloperidol (n = 233, 6 RCTs, RR 0.13, 95% CI 0.04 to 0.41, low quality evidence).Benzodiazepines versus combined antipsychotics/antihistaminesWhen benzodiazepine was compared with combined antipsychotics/antihistamines (haloperidol plus promethazine), there was a higher risk of no improvement in people receiving benzodiazepines in the medium term (n = 200, 1 RCT, RR 2.17, 95% CI 1.16 to 4.05, low quality evidence). However, for sedation, the results were controversial between two groups: lorazepam may lead to lower risk of sedation than combined antipsychotics/antihistamines (n = 200, 1 RCT, RR 0.91, 95% CI 0.84 to 0.98, low quality evidence); while, midazolam may lead to higher risk of sedation than combined antipsychotics/antihistamines (n = 200, 1 RCT, RR 1.13, 95% CI 1.04 to 1.23, low quality evidence).Other combinationsData comparing benzodiazepines plus antipsychotics versus benzodiazepines alone did not yield any results with clear differences; all were very low quality evidence. When comparing combined benzodiazepines/antipsychotics (all studies compared haloperidol) with the same antipsychotics alone (haloperidol), there was no difference between groups in improvement in the medium term (n = 185, 4 RCTs, RR 1.17, 95% CI 0.93 to 1.46, low quality evidence), but sedation was more likely in people who received the combination therapy (n = 172, 3 RCTs, RR 1.75, 95% CI 1.14 to 2.67,very low quality evidence). Only one study compared combined benzodiazepine/antipsychotics with antipsychotics; however, this study did not report our primary outcomes. One small study compared combined benzodiazepines/antipsychotics with combined antihistamines/antipsychotics. Results showed a higher risk of no clinical improvement (n = 60, 1 RCT, RR 25.00, 95% CI 1.55 to 403.99, very low quality evidence) and sedation status (n = 60, 1 RCT, RR 12.00, 95% CI 1.66 to 86.59, very low quality evidence) in the combined benzodiazepines/antipsychotics group.

AUTHORS' CONCLUSIONS

The evidence from RCTs for the use of benzodiazepines alone is not good. There were relatively few good data. Most trials were too small to highlight differences in either positive or negative effects. Adding a benzodiazepine to other drugs does not seem to confer clear advantage and has potential for adding unnecessary adverse effects. Sole use of older antipsychotics unaccompanied by anticholinergic drugs seems difficult to justify. Much more high-quality research is still needed in this area.

Re-examining the role of benzodiazepines in the treatment of schizophrenia: a systematic review

BACKGROUND

Benzodiazepine prescribing for schizophrenia occurs in clinical practice and antipsychotic trials. This review examined the clinical outcomes for benzodiazepines in schizophrenia.

METHOD

A systematic search identified randomised controlled trials that evaluated benzodiazepines in comparison with placebo or antipsychotics, and also as adjuncts to antipsychotics. Relevant clinical outcome data was extracted.

RESULTS

Twenty six studies were included with some reporting multiple comparisons. Seven short-term studies compared benzodiazepines with placebo: benzodiazepine superiority was found in two out of five studies for global improvements and two out of four studies for psychiatric/behavioural outcomes. Eleven studies compared benzodiazepines with first-generation antipsychotics (FGAs): four out of nine studies (including two long-term studies) reported greater global improvements for antipsychotics; four out of five studies showed no treatment differences for psychiatric/behavioural outcomes. Fourteen studies compared benzodiazepines (as adjunct to antipsychotics) vs antipsychotics alone (mostly FGAs); benzodiazepine superiority was found for global improvement in one out of eight studies and inferiority in two out of eight short-term studies whereas superiority was found for psychiatric/behavioural outcomes in three out of 12 short-term studies and inferiority in three out of 12 studies.

CONCLUSION

Benzodiazepine superiority over placebo was found for global, psychiatric and behavioural outcomes, but inferiority to antipsychotics on longer-term global outcomes. Conflicting evidence exists regarding the addition of benzodiazepines to antipsychotics; thus the use of benzodiazepines in clinical practice and antipsychotic trials should be limited.

Benzodiazepine augmentation of antipsychotic drugs in schizophrenia: a meta-analysis and Cochrane review of randomized controlled trials

Applying various psychopharmacological combination and augmentation strategies in schizophrenia is common clinical practice. This meta-analysis evaluated the efficacy of benzodiazepines added to antipsychotics. The Cochrane Schizophrenia Group trial register (until February 2011) and PubMed/Medline (until July 2012) were searched for randomized controlled trials (RCTs) with a minimum duration of one week that compared benzodiazepine augmentation of antipsychotics with a control group receiving antipsychotic monotherapy in schizophrenia and schizophrenia-like psychoses. Study selection and data extraction were conducted independently by at least two authors. The primary outcome was response to treatment. Secondary outcomes were positive and negative schizophrenic symptoms, anxiety symptoms, and dropouts due to any reason, inefficacy of treatment, and adverse events. Pooled risk ratios (RRs) with the 95% confidence intervals (CIs) were calculated using a random-effects model, with number-needed-to-treat/harm (NNT/H) calculations where appropriate. Overall, 16 relevant RCTs with 1045 participants were identified. Benzodiazepine augmentation was not associated with statistically significantly more responders (N=6; n=511; RR 0.97, 95% CI 0.77-1.22). Adjunctive benzodiazepines were well accepted and tolerated according to dropout-rates and adverse effects apart from dizziness (N=3; n=190; RR 2.58, 95% CI 1.08-6.15) and somnolence (N=2; n=118; RR 3.30, 95% CI 1.04-10.40). There is no evidence for antipsychotic efficacy of additional benzodiazepine medication in schizophrenia. Therefore, benzodiazepines should be considered primarily for desired ultra short-term sedation of acutely agitated patients but not for augmentation of antipsychotics in the medium- and long-term pharmacotherapy of schizophrenia and related disorders.

Benzodiazepines for schizophrenia

BACKGROUND

Because of the high number of people with schizophrenia not responding adequately to monotherapy with antipsychotic agents, the evidence regarding the efficacy and safety of additional medication was examined in a number of clinical trials. One approach to this research question was the use of benzodiazepines, as monotherapy as well as in combination with antipsychotics.

OBJECTIVES

To determine the efficacy, acceptability, and tolerability of benzodiazepines in people with schizophrenia and schizophrenia-like psychoses.

SEARCH METHODS

In February 2011, we updated the literature search of the previous version of this systematic review (last search March 2005). We searched the trial register of the Cochrane Schizophrenia Group (containing methodical searches of BIOSIS, CINAHL, Dissertation abstracts, EMBASE, LILACS, MEDLINE, PSYNDEX, PsycINFO, RUSSMED, Sociofile, supplemented with hand searching of relevant journals and numerous conference proceedings). Additionally, we inspected references of all identified studies for further relevant studies and contacted authors of relevant publications in order to obtain missing data from existing trials. We applied no language restrictions.

SELECTION CRITERIA

We included all randomised controlled trials comparing benzodiazepines (as monotherapy or as adjunctive agent) with antipsychotic drugs or placebo for the pharmacological management of schizophrenia and/or schizophrenia-like psychoses.

DATA COLLECTION AND ANALYSIS

Review authors (MD and CL) analysed independently the new references of the update-search referring to the inclusion criteria. MD and CL extracted all data from the included trials. For dichotomous outcomes we calculated risk ratios (RR) and their 95% confidence intervals (CI). We analysed continuous data by using mean differences (MD) and their 95% CI. We assessed each pre-selected outcome from the included trials with the risk of bias tool.

MAIN RESULTS

The 2011 update search yielded three further randomised controlled trials. The review currently includes 34 studies with 2657 participants. Most studies were characterised by a small sample size, short duration, and incomplete outcome data reporting.Benzodiazepine monotherapy is compared with placebo in eight trials. The proportion of participants with no clinically important response did not significantly differ between those given benzodiazepines or placebo (N = 382, 6 RCTs, RR 0.67 CI 0.44 to 1.02). The results from the various rating scales applied to assess global and mental state were inconsistent.Fourteen studies examined benzodiazepine monotherapy in comparison with antipsychotic monotherapy. Clinically important treatment response assessment revealed no statistically significant difference between the study groups (30 minutes: N = 44, 1 RCT, RR 0.91 CI 0.58 to 1.43; 60 minutes: N = 44,1 RCT, RR 0.61 CI 0.20 to 1.86; 12 hours: N = 66, 1 RCT, RR 0.75 CI 0.44 to 1.30; pooled short-term studies: N = 112, 2 RCTs, RR 1.48 CI 0.64 to 3.46). Desired sedation occurred significantly more often among participants in the benzodiazepine group than in the antipsychotic group at 20 and 40 minutes. No significant between-group differences could be identified for global and mental state or occurrence of adverse effects.Twenty trials compared benzodiazepine augmentation of antipsychotics with antipsychotic monotherapy. Referring to clinically important response, statistically significant improvement could be demonstrated only for the first 30 minutes of augmentation treatment (30 minutes: 1 RCT, N = 45, RR 0.38 CI 0.18 to 0.80; 60 minutes: N = 45,1 RCT, RR 0.07 CI 0.00 to 1.13; 12 hour: N = 67,1 RCT, RR 0.85 CI 0.51 to 1.41; pooled short-term studies: N = 511, 6 RCTs, RR 0.87 CI 0.49 to 1.54). Analyses of the global and mental state yielded no between-group differences except for desired sedation at 30 as well as 60 minutes (30 minutes: N = 45, 1 RCT, RR 2.25 CI 1.18 to 4.30; 60 minutes: N = 45, 1 RCT, RR 1.39 CI 1.06 to 1.83).

AUTHORS' CONCLUSIONS

There is currently no convincing evidence to confirm or refute the practise of administering benzodiazepines as monotherapy or in combination with antipsychotics for the pharmacological treatment of schizophrenia and schizophrenia-like psychosis. Low-quality evidence suggests that benzodiazepines are effective for very short-term sedation and could be considered for calming acutely agitated people with schizophrenia. Measured by the overall attrition rate, the acceptability of benzodiazepine treatment appears to be adequate. Adverse effects were generally poorly reported. High-quality future research projects with large sample sizes are required to clarify the evidence of benzodiazepine treatment in schizophrenia, especially regarding long-term augmentation strategies.

Role of Haloperidol in Palliative Medicine

Haloperidol is a butyrophenone neuroleptic agent characterized as a high-affinity dopamine antagonist, originally used for the treatment of schizophrenia. Awareness of the role dopamine plays in many symptoms in palliative care, such as nausea, vomiting, and delirium, has led to the use of dopamine antagonists such as haloperidol for the treatment of these symptoms in the palliative care setting. Listed as 1 of the 25 important drugs in palliative care, haloperidol can be administered by multiple routes and can be given without dose alteration in the setting of both renal and hepatic insufficiency. Haloperidol is extensively metabolized in the liver, with CYP3A4 the chief cytochrome oxidase responsible for metabolism. This article will review the pharmacology, pharmacokinetics, and current uses of haloperidol in palliative medicine. There will be an examination of the evidence base for the use of haloperidol in palliative medicine.

Benzodiazepines for schizophrenia

BACKGROUND

Many people with schizophrenia do not achieve a satisfactory treatment response with ordinary antipsychotic drug treatment. In these cases, various add-on medications are used, among them benzodiazepines.

OBJECTIVES

To review the effects of benzodiazepines for the treatment of schizophrenia and schizophrenia-like psychoses.

SEARCH STRATEGY

The reviewers searched the Cochrane Schizophrenia Group's register (last search March 2005). This register is compiled by methodical searches of BIOSIS, CINAHL, Dissertation abstracts, EMBASE, LILACS, MEDLINE, PSYNDEX, PsycINFO, RUSSMED, Sociofile, supplemented with hand searching of relevant journals and numerous conference proceedings. We also contacted authors of relevant studies in order to obtain missing data from existing trials.

SELECTION CRITERIA

All randomised controlled trials comparing benzodiazepine to antipsychotics or to placebo (or no intervention), whether as sole treatment or as an adjunct to antipsychotic medication for the treatment of schizophrenia and/or schizophrenia-like psychoses.

DATA COLLECTION AND ANALYSIS

We independently inspected abstracts, selected studies and re-inspected and quality assessed the full reports. We independently extracted relevant outcomes. Dichotomous data were analysed using relative risks (RR) and the 95% confidence intervals (CI). Continuous data were analysed using weighted mean differences. Where possible the number needed to treat (NNT) or number needed to harm (NNH) statistics were calculated.

MAIN RESULTS

The review currently includes 31 studies with over 2000 participants. Most studies were small, of short duration - one to 13 weeks - and inconsistently and incompletely reported. Eight studies compared benzodiazepines as a sole agent with placebo. More participants receiving benzodiazepines showed a clinically significant response (n=222, 4 RCTs, RR 0.54 CI 0.3 to 1.0, NNT 3 CI 2 to 17). Only one small study found a significant group difference in favour of benzodiazepines regarding the improvement in overall BPRS mental state. Different rating scales were used to assess general mental state, and therefore many outcomes could not be pooled and no overall direction of effect emerged. Some adverse events observed in these studies suggested that benzodiazepines were more harmful than placebos but again the data were incompletely reported and without overall effect. Thirteen studies examined the effects of benzodiazepines in comparison to antipsychotics as a sole treatment. Trials that reported on clinical response found no advantage for any treatment group concerning improvement of the participants' global state, except of one small study that analysed the mean CGI severity score at one hour. This comparison is highly limited by the low numbers of studies reporting on global function and the short trial duration. Two studies showed a statistically significant superiority of antipsychotics in terms of relapse prevention at one year. Desired sedation occurred significantly more often among participants in the benzodiazepine group than among participants in the antipsychotic treatment group at 20 (n=301, 1 RCT, RR 1.32 CI 1.2 -1.5, NNT 5, CI 3 to 8) and 40 minutes(n= 301, 1 RCT, RR 1.13 CI 1.0 to 1.2, NNT 9 CI 6 to 33), but not at 30, 60 or 12 minutes. Other outcomes relating to the general or specific mental state revealed no significant differences between groups. As far as adverse events were reported there were no results in favour of any group. Sixteen studies examined whether the augmentation of antipsychotics with benzodiazepines is more effective than antipsychotics as a sole treatment. During the first hour of treatment the combination treatment group benefited from the additional benzodiazepine in terms of the participants global state. This benefit diminished over time and was not reproducible at 2 hours or longer. No superior efficacy of benzodiazepine augmentation could be found regarding the general mental state. Specific aspects of the mental state showed no group difference except for desired sedation at 30 and 60 minutes. Somnolence affected the combination treatment group significantly more than the control group (n=118, 2 RCTs, RR 3.30 CI 1.0 to 10.4, NNH 8 CI 5 to 50). We found use of antiparkinson medication to be less frequently used in the combination treatment group (n=282, RR 0.68 CI 0.5 to 1.0, NNT 9 CI 6 to 48). Adverse events were poorly reported and the results were based on very little data.

AUTHORS' CONCLUSIONS

Randomised trial-derived evidence is currently too poor to recommend benzodiazepines neither as a sole nor as an adjunctive agent in schizophrenia or schizophrenia-like psychoses. The only significant effects were seen in terms of short-term sedation, at best. The evidence available on augmentation of antipsychotics with benzodiazepines is inconclusive and justifies large, simple and well-designed future trials focusing on clinical response, mental state, aggressive behaviour and adverse events.

Pharmacokinetics of haloperidol: an update

Haloperidol is commonly used in the therapy of patients with acute and chronic schizophrenia. The enzymes involved in the biotransformation of haloperidol include cytochrome P450 (CYP), carbonyl reductase and uridine diphosphoglucose glucuronosyltransferase. The greatest proportion of the intrinsic hepatic clearance of haloperidol is by glucuronidation, followed by the reduction of haloperidol to reduced haloperidol and by CYP-mediated oxidation. In studies of CYP-mediated disposition in vitro, CYP3A4 appears to be the major isoform responsible for the metabolism of haloperidol in humans. The intrinsic clearances of the back-oxidation of reduced haloperidol to the parent compound, oxidative N-dealkylation and pyridinium formation are of the same order of magnitude, suggesting that the same enzyme system is responsible for the 3 reactions. Large variation in the catalytic activity was observed in the CYP-mediated reactions, whereas there appeared to be only small variations in the glucuronidation and carbonyl reduction pathways. Haloperidol is a substrate of CYP3A4 and an inhibitor, as well as a stimulator, of CYP2D6. Reduced haloperidol is also a substrate of CYP3A4 and inhibitor of CYP2D6. Pharmacokinetic interactions occur between haloperidol and various drugs given concomitantly, for example, carbamazepine, phenytoin, phenobarbital, fluoxetine, fluvoxamine, nefazodone, venlafaxine, buspirone, alprazolam, rifampicin (rifampin), quinidine and carteolol. Overall, drug interaction studies have suggested that CYP3A4 is involved in the biotransformation of haloperidol in humans. Interactions of haloperidol with most drugs lead to only small changes in plasma haloperidol concentrations, suggesting that the interactions have little clinical significance. On the other hand, the coadministration of carbamazepine, phenytoin, phenobarbital, rifampicin or quinidine affects the pharmacokinetics of haloperidol to an extent that alterations in clinical consequences would be expected. In vivo pharmacogenetic studies have indicated that the metabolism and disposition of haloperidol may be regulated by genetically determined polymorphic CYP2D6 activity. However, these findings appear to contradict those from studies in vitro with human liver microsomes and from studies of drug interactions in vivo. Interethnic and pharmacogenetic differences in haloperidol metabolism may explain these observations.

The relationship between serum concentration and therapeutic effect of haloperidol in patients with acute schizophrenia

Haloperidol is the most commonly used antipsychotic drug in the therapy of acute schizophrenia. Clinicians have been using therapeutic drug monitoring in an attempt to improve clinical application of this drug. The scale of interest in this area is emphasised by the large number of studies (about 50) concerning the serum concentration-therapeutic effect relationship (SCTER) of haloperidol, including 35 studies on patients with acute schizophrenia. However, conflicting results concerning the existence and position of a therapeutic window have emerged. This article aims to provide a comprehensive review of the study design of studies in patients with acute schizophrenia before the study data are used for decision-making. For this purpose, a reproducible system for the evaluation of studies in this special area, a so-called total study score (TSS), was developed on an empirical basis. Thus, insufficient study design was found to be a reason for negative results. On the other hand, in spite of a great variability, the majority of studies with good design provided evidence for a significant SCTER: a bisigmoidal dependence of clinical effect on haloperidol serum concentration. The therapeutic effects of haloperidol increase at low concentrations, and the concentration has a maximum effect at about 10 micrograms/L and again decreasing at higher concentrations. The data of 552 patients also fit to this model in a single scatter plot (pseudo-r2 = 0.076, p < 0.001). The position of the therapeutic window was determined at about 5.6 to 16.9 micrograms/L. Patients treated with serum concentrations within this optimal range had a significantly better response compared with outside this range (p < 0.001, Student t-test). Therefore, a quantitative synthesis of all available data by means of effect-size analysis provides a mean effect-size (g) = 0.499 +/- 0.182 (standard deviation) for the comparison of haloperidol-treatment with serum concentrations within versus outside the therapeutic window. Thus, because of this moderate positive effect, serum concentration assay of haloperidol is recommended for patients with acute schizophrenia in a therapeutic drug monitoring programme. The modalities of haloperidol therapeutic drug monitoring in clinical practice are discussed, e.g. patient selection, method and time for serum concentration measurement, influence of premedication and comedication, interpretation of results and dose adjustment. Clinical investigations into this subject should focus on covariates which are responsible for the variability of the SCTER. Serum concentration assay is advised for investigations of nonresponse to exclude patients with pseudo-drug resistance.