Haloperidol plasma levels and clinical response in paranoid schizophrenics

Mechanisms of action of antipsychotic drugs of different classes, refractoriness to therapeutic effects of classical neuroleptics, and individual variation in sensitivity to their actions: Part II

Rapid-onset psychotic rebound is uncommon on discontinuation of most antipsychotic drugs, as might be expected for antipsychotic drugs with (hypothetically) indirect actions at their final target receptors. Rapid-onset psychosis is more common on withdrawal of clozapine, which might be expected if its action is direct. Drugs other than clozapine (notably thioridazine) may have hitherto unrecognised similarities to clozapine (but without danger of agranulocytosis), and may be useful in treatment of refractory psychosis. Quetiapine fulfils only some criteria for a clozapine-like drug. Clinical response to neuroleptics varies widely at any given plasma level. Haase's "neuroleptic threshold" concept suggests that the dose producing the slightest motor side effects produces most or all of the therapeutic benefit, but analyses presented here suggest that antipsychotic actions are not subject to a sharp "all-or-none" threshold but increase over a small dose range. This concept could provide a method for quantitative determination of individualized optimal doses.

Gender-specific prolactin response to antipsychotic treatments with risperidone and olanzapine and its relationship to drug concentrations in patients with acutely exacerbated schizophrenia

Hyperprolactinemia is a frequent consequence of treatment with antipsychotic agents, partially because the prolactin response to antipsychotics is related to dopamine blockade. Recent studies have suggested that the prolactin response to olanzapine is weaker than that to risperidone. Thus, we studied the effects of various factors on the elevated plasma prolactin levels caused by these medications. The subjects were 94 patients with acutely exacerbated schizophrenia (46 males, 48 females). For four weeks, they received 6mg of risperidone and 20mg of olanzapine daily. Plasma samples were collected before the medications were given and 12h after the bedtime dosing each week. Treatment with either risperidone or olanzapine boosted plasma prolactin levels above baseline in both males and females. Prolactin levels were significantly higher in females than in males at all sampling points in both treatments. Risperidone increased prolactin significantly more than did olanzapine in both males and females. Delta prolactin (prolactin level at four weeks minus the baseline prolactin level) during olanzapine treatment significantly correlated with olanzapine concentration at 4th week (r=-0.518, p<0.01) only in males. Multiple regression analyses showed that delta prolactin during risperidone was significantly correlated with gender (p<0.001) and age (p<0.05) and that delta prolactin during olanzapine significantly correlated with gender (p<0.001) and drug concentration (p<0.01). The present study suggests that the predominant factors influencing hyperprolactinemia are young female for risperidone treatment, and being female and lower drug concentration as a predictor for hyperprolactinemia under olanzapine.

Prolactin fluctuation over the course of a day during treatments with three atypical antipsychotics in schizophrenic patients

Hyperprolactinemia is a frequent consequence of treatment with some antipsychotic agents. Although prolactin secretion varies over the course of a day and during psychological circumstances, there is little information in the literature regarding the time dependence of the prolactin response to antipsychotics. We evaluated prolactin levels in schizophrenic patients receiving risperidone (3 mg twice daily), olanzapine (10 mg twice daily), or perospirone (16 mg twice daily) for at least 4 weeks. The subjects were compared to matched healthy controls. Plasma sample collection for quantification of drug and prolactin levels was conducted before and 2, 4, 6, 8, and 12 h after the morning dosing. Prolactin concentrations before dosing during risperidone treatment were significantly higher than during treatment with olanzapine and perospirone in females. The daily fluctuation of prolactin concentration after perospirone treatment was larger than that observed after risperidone and olanzapine treatments. Areas under the plasma concentration-time curves was greatest in subjects treated with risperidone, followed by perospirone and finally by olanzapine. These findings suggest that daily fluctuations in prolactin concentration after perospirone treatment are larger than following treatment with risperidone and olanzapine. The plasma concentration of prolactin during perospirone treatment therefore depends on the time of sampling.

Estimates of serotonin and norepinephrine transporter inhibition in depressed patients treated with paroxetine or venlafaxine

Paroxetine and venlafaxine are potent serotonin transporter (SERT) antagonists and weaker norepinephrine transporter (NET) antagonists. However, the relative magnitude of effect at each of these sites during treatment is unknown. Using a novel blood assay that estimates CNS transporter occupancy we estimated the relative SERT and NET occupancy of paroxetine and venlafaxine in human subjects to assess the relative magnitude of SERT and NET inhibition. Outpatient subjects (N=86) meeting criteria for major depression were enrolled in a multicenter, 8 week, randomized, double-blind, parallel group, antidepressant treatment study. Subjects were treated by forced-titration of paroxetine CR (12.5-75 mg/day) or venlafaxine XR (75-375 mg/day) over 8 weeks. Blood samples were collected weekly to estimate transporter inhibition. Both medications produced dose-dependent inhibition of the SERT and NET. Maximal SERT inhibition at week 8 for paroxetine and venlafaxine was 90% (SD 7) and 85% (SD 10), respectively. Maximal NET inhibition for paroxetine and venlafaxine at week 8 was 36% (SD 19) and 60% (SD 13), respectively. The adjusted mean change from baseline (mean 28.6) at week 8 LOCF in MADRS total score was -16.7 (SE 8.59) and -17.3 (SE 8.99) for the paroxetine and venlafaxine-treated patients, respectively. The magnitudes of the antidepressant effects were not significantly different from each other (95%CI -3.42, 4.54, p=0.784). The results clearly demonstrate that paroxetine and venlafaxine are potent SERT antagonists and less potent NET antagonists in vivo. NET antagonism has been posited to contribute to the antidepressant effects of these compounds. The clinical significance of the magnitude of NET antagonism by both medications remains unclear at present.

Association between dopamine-related polymorphisms and plasma concentrations of prolactin during risperidone treatment in schizophrenic patients

Hyperprolactinemia is an inevitable consequence of treatment with antipsychotic agents to some extent because prolactin response to antipsychotics is related to dopamine blockade. Recent studies have suggested that polymorphisms of the dopamine receptors are associated with therapeutic response to antipsychotics. Thus, we studied the effects of major polymorphisms of dopamine-related genes on plasma concentration of prolactin. Subjects were 174 schizophrenic patients (68 males, 106 females) receiving 3 mg twice daily of risperidone for at least 4 weeks. Sample collections were conducted 12 h after the bedtime dosing. Five dopamine-related polymorphisms (Taq1A, -141C ins/del for DRD2, Ser9Gly for DRD3, 48 bp VNTR for DRD4, Val158Met for COMT) were identified. The mean (+/-SD) plasma concentration of prolactin in females was significantly higher than males (54.3+/-27.2 ng/ml versus 126.8+/-70.2 ng/ml, p<0.001). No dopamine-related polymorphisms differed the plasma concentration of prolactin in males or females. Multiple regression analyses including plasma drug concentration and age revealed that plasma concentration of prolactin correlated with gender (standardized partial correlation coefficients (beta)=0.551, p<0.001) and negatively with age (standardized beta=-0.202, p<0.01). No correlations were found between prolactin concentration and dopamine-related polymorphisms. These findings suggest that plasma prolactin concentrations in females are much higher than in males but the dopamine-related variants are not predominantly associated with plasma concentration of prolactin.

Clinical implications of antipsychotic-induced hyperprolactinemia in patients with schizophrenia spectrum or bipolar spectrum disorders: recent developments and current perspectives

Hyperprolactinemia is increasingly studied as a frequent and potentially important consequence of antipsychotic medication treatment. Some individuals presenting with hyperprolactinemia remain asymptomatic, but others may exhibit a wide range of clinical symptoms resulting from either the direct effects of prolactin on body tissues (galactorrhea, gynecomastia) or endocrine-related secondary effects (sexual and reproductive dysfunction in the short term, and possibly the risk of tumorigenesis and osteoporosis in the longer term). Short-term side effects may negatively impact medication compliance, and long-term effects have the potential for serious health consequences. Antipsychotic medications have differing propensities to cause prolactin elevation. The first-generation antipsychotics, as well as the second-generation antipsychotic risperidone and its active metabolite paliperidone, have been shown to cause marked and sustained elevations in prolactin levels, whereas others of the second-generation antipsychotics appear to have little or no effect on prolactin levels or may decrease prolactin. A comprehensive overview of antipsychotics and hyperprolactinemia is presented together with a review of emerging evidence about the short- and long-term health risks of hyperprolactinemia.

Plasma antipsychotic concentration and receptor occupancy, with special focus on risperidone long-acting injectable

Although effective plasma concentration ranges have been established for some antipsychotics, conventional and atypical, there is considerable inter-patient pharmacokinetic variation. Positron-emission tomography (PET) can be used to estimate D(2)-like receptor occupancy in the brain needed for an antipsychotic effect and the level above which extrapyramidal side effects (EPS) develop. For conventional antipsychotics, the window occupancy is approximately 70-80%. For the atypical antipsychotic risperidone, the antipsychotic effect starts at approximately 60% occupancy, with occupancy above 80% leading to EPS. The new formulation, risperidone long-acting injectable (RLAI), comprises risperidone in a biodegradable polymer. It is effective long-term at doses of 25 or 50 mg injected i.m. every 2 weeks. The constant and slow release of the long-acting formulation leads to less fluctuation in plasma levels and to a D(2)-like receptor occupancy which is below the threshold for EPS.

Receptor occupancy-based analysis of the contributions of various receptors to antipsychotics-induced weight gain and diabetes mellitus

OBJECTIVE

Among various adverse reactions of atypical antipsychotics, weight gain and impaired glucose tolerance are clinically significant. The aim of this study is to analyze quantitatively the contributions of various receptors to these antipsychotics-induced adverse reactions based on the receptor occupancy theory.

METHODS

Two indices of antipsychotics-induced weight gain (the values estimated by a meta-analysis and the observed values in clinical trials) and the morbidity rate of type 2 diabetes mellitus during treatment with antipsychotics were taken from the literature. We calculated the estimated mean receptor occupancies of alpha1 adrenergic, alpha2 adrenergic, dopamine D2, histamine H1, muscarinic acetylcholine (mACh), serotonin 5-HT1A, 5-HT2A and 5-HT2C receptors by antipsychotics by using the pharmacokinetic parameters and receptor dissociation constants, and analyzed the correlation between the occupancies and the extent of adverse reactions as assessed using the aforementioned indices.

RESULTS

There were statistically significant correlations between the estimated occupancies of H1 and mACh receptors and antipsychotics-induced weight gain estimated by meta-analysis (r(s) = 0.81 and r(s) = 0.83, respectively, p < 0.01). There were also statistically significant correlations between these receptor occupancies and observed weight gain in clinical trials (r(s) = 0.66 in each case, p < 0.01). The morbidity rate of type 2 diabetes mellitus was highly correlated with H1, mACh, and 5-HT2C receptor occupancies (r(s) = 0.90 in each case, p < 0.05). However, H1 receptor occupancy was also highly correlated with mACh receptor occupancy among antipsychotics, so that only one of them may be critically associated with the adverse reactions. Considering that these adverse reactions have not been reported for drugs with mACh receptor antagonistic action, other than antipsychotics, the H1 receptor may contribute predominantly to the antipsychotics-induced weight gain and diabetes mellitus.

DISCUSSION/CONCLUSION

Model analysis based on receptor occupancy indicates that H1 receptor blockade is the primary cause of antipsychotics-induced weight gain and diabetes mellitus.

Pharmacokinetic-Pharmacodynamic Analysis of Antipsychotics-induced Extrapyramidal Symptoms based on Receptor Occupancy Theory Incorporating Endogenous Dopamine Release

We aimed to analyze the risks of extrapyramidal symptoms (EPS) induced by typical and atypical antipsychotic drugs using a common pharmacokinetic-pharmacodynamic (PK-PD) model based on the receptor occupancy. We collected the data for EPS induced by atypical antipsychotics, risperidone, olanzapine and quetiapine, and a typical antipsychotic, haloperidol from literature and analyzed the following five indices of EPS, the ratio of patients obliged to take anticholinergic medication, the occurrence rates of plural extrapyramidal symptoms (more than one of tremor, dystonia, hypokinesia, akathisia, extrapyramidal syndrome, etc.), parkinsonism, akathisia, and extrapyramidal syndrome. We tested two models, i.e., a model incorporating endogenous dopamine release owing to 5-HT2A receptor inhibition and a model not considering the endogenous dopamine release, and used them to examine the relationship between the D2 receptor occupancy of endogenous dopamine and the extent of drug-induced EPS. The model incorporating endogenous dopamine release better described the relationship between the mean D2 receptor occupancy of endogenous dopamine and the extent of EPS than the other model, as assessed by the final sum of squares of residuals (final SS) and Akaike's Information Criteria (AIC). Furthermore, the former model could appropriately predict the risks of EPS induced by two other atypical antipsychotics, clozapine and ziprasidone, which were not incorporated into the model development. The developed model incorporating endogenous dopamine release owing to 5-HT2A receptor inhibition may be useful for the prediction of antipsychotics-induced EPS.

Extracting numerical data from published reports of pharmacokinetics investigations: method description and validation

A method has been proposed for extracting numerical data when only graphical results are presented. Reports with both graphical and tabular data were identified and the graphs were electronically scanned. The coordinates of each point were read using the cross-hair facility of Adobe Photoshop 7.0. To improve the precision of these coordinates, each point was read at 1600% magnification. The agreement between the observers was almost perfect (R > 0.99). The proposed method makes possible use of data in meta-analyses that, would otherwise be discarded.

Correlation of antipsychotic and prolactin concentrations in children and adolescents acutely treated with haloperidol, clozapine, or olanzapine

Patients with a Diagnostic and Statistical Manual of Mental Disorders (third edition, revised) diagnosis of schizophrenia or psychotic disorder not otherwise specified with onset of psychosis before the age of 13 participated in 6- to 8-week open or double-blind trials of haloperidol (n = 15, mean dose 15.4 +/- 8.1 mg/day [0.27 +/- 0.15 mg/kg/day]), clozapine (n = 30, mean dose 269.9 +/- 173.3 mg/day [4.4 +/- 2.6 mg/kg/day]), or olanzapine (n = 12, mean dose 17.5 +/- 2.8 mg/day [0.30 +/- 0.13 mg/kg/day]). Blood samples were obtained at 6 weeks for evaluation of haloperidol, reduced haloperidol, clozapine, desmethylclozapine, and olanzapine plasma concentrations and serum prolactin concentrations. No gender differences were noted for antipsychotic dose or concentration within each treatment group. Correlations between antipsychotic plasma concentration and serum prolactin concentration were significant only for the olanzapine treatment group (r = 0.80, p = 0.002). Separate correlations for gender were significant only for females receiving olanzapine (r = 0.91, p = 0.03); the patient with the highest serum prolactin experienced galactorrhea. Further studies evaluating the prolactin-elevating properties of antipsychotics are warranted in this population.

Comparison of prolactin concentrations between haloperidol and bromperidol treatments in schizophrenic patients

The antipsychotic drug, bromperidol, is a close structural analogue of haloperidol. These two drugs also have similarities in metabolic pathways and pharmacological properties. In the present study, the prolactin concentrations in plasma during bromperidol versus haloperidol treatments were compared in the same individuals. The subjects were 22 schizophrenic inpatients, who first received bromperidol 12 mg/day for at least 2 weeks followed by haloperidol 12 mg/day. The prolactin concentration in plasma during bromperidol treatment (median and range; 24 and 7-93 ng/ml, respectively) was significantly (P< .01) lower than during haloperidol treatment (32 and 8-102 ng/ml), although the difference was small. The mean (+/- S.D.) plasma concentration of bromperidol was significantly lower than that of haloperidol (20.8+/-8.0 vs. 28.0+/-13.1 nmol/l, P<.05). Prolactin concentrations during both treatment phases correlated well in individuals (r's=.813, P<.001), while no correlation was observed between plasma concentrations of haloperidol and bromperidol (r=.053, ns). These findings suggest that slightly higher prolactin concentration does not necessarily lead to increased risk of hyperprolactinemia during bromperidol treatment compared with haloperidol treatment. In addition, it is suggested that both drugs show similar pharmacodynamic response despite the difference in pharmacokinetics in the same individuals.

Associations between side effects of nemonapride and plasma concentrations of the drug and prolactin

Associations between neuroleptic side effects and plasma concentrations of the drug and prolactin were investigated in 33 acutely exacerbated schizophrenic patients (16 males and 17 females) treated with a fixed dose of nemonapride (18 mg/day), a new substituted benzamide, for 3 weeks. The most frequently observed side effects during nemonapride treatment were extrapyramidal symptoms such as akathisia (69.7%), dystonia (48.5%), hypokinesia (45.5%), tremor (39.4%) and increased salivation (36.4%). There were positive correlations between prolactin response and extrapyramidal side effects (EPS) scores after 1 week (Spearman rank correlation rs=.651, P<.01), 2 weeks (rs=.567, P<.05) and 3 weeks (rs=.670, P<.01) in male patients although no significant correlations were found in female or total patients. No significant correlations were found between plasma concentrations of the drug and total or any subscale side effects scores. The present study thus suggests that the spectrum of nemonapride-induced side effects is characterized by predominant extrapyramidal symptoms, and that prolactin response as an index of dopamine blockade reflects severity of EPS at least in male patients treated with nemonapride.

Relationship between Taq1 A dopamine D2 receptor (DRD2) polymorphism and prolactin response to bromperidol

The dopamine D2 receptor (DRD2) gene has a Taq1 A restriction fragment length polymorphism yielding two alleles, A1 and A2. We have previously shown that female patients with the A1 allele show greater prolactin response to nemonapride, a selective antagonist for D2-like dopamine receptors, in schizophrenic patients. In the present study, the relationship between this polymorphism and prolactin response to bromperidol was investigated in 32 untreated schizophrenic inpatients (16 males, 16 females). The daily dose of bromperidol was fixed at 6 (n = 10), 12 (n = 13), or 18 mg (n = 9) during a 2-week treatment period. Taq1 A genotypes were determined by PCR method. Plasma prolactin concentration was measured by radioimmunoassay. Plasma concentration of bromperidol was measured by HPLC method. The subjects were divided into four subgroups by gender and the genotypes, i.e., 10 males and 11 females with the A1 allele, 6 males and 5 females with no A1 allele. The females with the A1 allele had the highest Delta prolactin (the change from the pretreatment concentration)/bromperidol concentration ratio among the other groups (P < 0.05). The present study thus suggests that female patients with the A1 allele show greater prolactin response to bromperidol, who may have a high risk for adverse effects associated with neuroleptic-induced hyperprolactinemia.

Therapeutic spectrum of nemonapride and its relationship with plasma concentrations of the drug and prolactin

The therapeutic spectrum of nemonapride, a new substituted benzamide, and its relationship with plasma concentrations of the drug and prolactin were investigated by a fixed-dose study (18 mg/day for 3 weeks) in 31 patients with acutely exacerbated schizophrenia. Of 31 patients, 25 (80.6%) were responders who showed a reduction in symptoms (percentage of improvement) of 50% or more after 3 weeks. The mean values of percentage of improvement in scores on the total Brief Psychiatric Rating Scale (BPRS) and the five subscale symptoms were 71.5% for total, 73.2% for Positive, 86.0% for Excitement, 53.9% for Negative, 84.2% for Cognitive, and 67.5% for Anxiety-Depression. Responders had higher percentage of improvement in positive (84.6 +/- 17.0% vs. 25.9 +/- 15.7%; p < 0.001) and anxiety-depression (76.9 +/- 18.8% vs. 28.5 +/- 39.9%; p < 0.005) symptoms than did nonresponders after 3 weeks. The percentage of improvement in total BPRS after 2 weeks was well correlated with that after 3 weeks (Spearman rank correlation coefficient: r(s) = 0.711; p < 0.01). There was an inverted U-shaped relationship between plasma drug concentrations (nemonapride plus desmethylnemonapride) and percentage of improvement in total BPRS symptoms after a 3-week treatment (y = 46.9 + 73.9x - 44.2x2; p < 0.001). These findings suggest that nemonapride has a broad therapeutic spectrum in the treatment of acute schizophrenia. The improvements in scores for the Positive and Anxiety-Depression subscale symptoms are regarded as determinant factors for total response to nemonapride. An assessment of clinical status after 2 weeks and plasma drug monitoring may be useful for the prediction of the final outcome for patients.

Characteristics and risk factors of acute dystonia in schizophrenic patients treated with nemonapride, a selective dopamine antagonist

The occurrence of acute dystonia was prospectively monitored in 39 schizophrenic patients (18 male and 21 female) treated with 9 to 27 mg/day of nemonapride, a selective dopamine antagonist, and the relationship of acute dystonia with characteristics of patients and plasma concentrations of the drug and prolactin was investigated. Twenty (51.3%) of 39 patients had dystonic reactions, the onsets of which occurred within 3 days after the initiation of treatment in 90% of dystonic patients. The incidence of acute dystonia was significantly higher in male than in female patients (77.8% vs. 28.6%, p < 0.05). Younger male patients (< or = 30 years) especially had an extremely high incidence of this side effect (91.7%). A positive correlation between prolactin response after 1 week of treatment and dystonia rating scores was found in male (Spearman rank correlation: r(s) = 0.606,p < 0.01) but not in female patients (r(s) = -0.378,p = not significant). These results suggest that young male patients have the highest risk of neuroleptic-induced dystonia. Prolactin response after 1 week of treatment as an index of dopamine blockade may reflect vulnerability to the development of acute dystonia at least in male patients treated with nemonapride.

Neuroendocrine response to antipsychotics: effects of drug type and gender

BACKGROUND

To study the influences of drug type and gender on the neuroendocrine response to neuroleptic treatment, we compared the endocrine actions of two neuroleptics with different receptor affinity profiles--a substituted benzamide, amisulpride, a selective D2-like dopamine antagonist; and a thioxanthene, flupenthixol, a mixed D1/D2-like antagonist also blocking serotonin, H1, and D1 receptors--on anterior pituitary hormone secretion in schizophrenic patients (DSM-III-R).

METHODS

Blood was withdrawn at 15-min intervals to assess basal secretion of prolactin, growth hormone (GH), and thyroid-stimulating hormone (TSH). Four hundred micrograms of thyrotropin-releasing hormone (TRH) was injected i.v. to investigate drug effects on TRH-stimulated secretion of prolactin, TSH, and GH.

RESULTS

Prolactin plasma levels were markedly elevated in both treatment groups. In female, but not in male patients, this elevation was significantly more pronounced under amisulpride than under flupenthixol. The prolactin response to TRH was significantly blunted by amisulpride only in male subjects. While basal TSH secretion was significantly increased by both compounds, TRH-stimulated TSH secretion was elevated only in patients treated with amisulpride. Low basal prolactin levels predicted improvement of negative symptoms in patients treated with amisulpride.

CONCLUSIONS

Amisulpride's more pronounced endocrine effects may be a reflection of its distinguished pharmacology and pharmacokinetics.

Change in plasma prolactin and clinical response to haloperidol in schizophrenia and schizoaffective disorder

There has been a long-standing interest in plasma prolactin as a potential in vivo indicator of blockade of tuberoinfundibular D2 dopamine receptors. Potential relationships between prolactin response and neuroleptic treatment have been obscured by the use of high doses which have caused prolactin to plateau. With lower doses of neuroleptic now commonly in use, prolactin may be more valuable as a correlate of clinical response. In this study, 23 acutely exacerbated schizophrenic and schizoaffective patients were washed out for at least 6 days and were then treated with haloperidol to achieve fixed low to moderate plasma levels under double-blind conditions. Clinical response, plasma prolactin, and haloperidol plasma levels were measured weekly for 3 weeks. Clinical symptoms at endpoint were related to both prolactin change and final prolactin level during haloperidol treatment. Specifically, fewer symptoms at endpoint were associated with a greater increase in prolactin over time and a higher prolactin level at endpoint. Thus, prolactin increase caused by low to moderate doses of haloperidol may be a correlate of endpoint symptomatology. As lower doses of typical neuroleptics are now in use, prolactin response as a predictor of clinical response may have more clinical utility. Further study of prolactin and clinical response to typical neuroleptics should focus on low neuroleptic doses.

Prolactin response to bromperidol treatment in schizophrenic patients

The prolactin response to an antipsychotic drug, bromperidol was studied in 24 schizophrenic in-patients (13 males. 11 females). Eight patients were given 6 mg/day, 8 were given 18 mg/day. Duration of treatment was 3 weeks. Plasma concentrations of bromperidol and reduced bromperidol were measured by high-performance liquid chromatography, and that of prolactin was measured by radioimmunoassay. Bromperidol treatment significantly (P < 0.01) increased plasma concentration of prolactin each week. The mean +/- S.D. of the delta-prolactin (the mean concentration during treatment minus the pretreatment concentration) was 13.3 +/- 12.4 ng/ml. Multiple regression analysis showed that the delta-prolactin concentration was significantly greater in females than in males (P < 0.05) and correlated to plasma concentrations of bromperidol (P < 0.001) and reduced bromperidol (P < 0.0001). These results suggest that the prolactin response to bromperidol treatment depend on plasma concentrations of both bromperidol and reduced bromperidol and gender, and that reduced bromperidol is involved in the pharmacological effects during bromperidol treatment.

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.

A two-phase, double-blind randomized study of three haloperidol plasma levels for acute psychosis with reassignment of initial non-responders

To clarify the plasma level/therapeutic response relationship of haloperidol (HPDL) we used a prospective double-blind design in 95 acutely psychotic patients. After drug washout, patients were randomly assigned to a low, middle or high plasma level range for 2 weeks (phase A), and then 50% of the initial non-responders were randomly reassigned into the putative therapeutic range for an additional 2 weeks (phase B). There were no significant differences in clinical outcome between the three plasma level ranges in phase A. However, in phase B initial non-responders displayed greater improvement in the middle range than in the low or the high ranges. No further benefit was observed when plasma levels were raised to or maintained in the high range.

Haloperidol blood levels and clinical outcome: a meta-analysis of studies relevant to testing the therapeutic window hypothesis

Haloperidol, the most studied antipsychotic drug, is the only one about which reliable statements on the relationship between blood levels and clinical outcome can be made. A systematic overview was undertaken to determine whether there was an optimum blood concentration range for clinical efficacy. Eighteen published studies which provided individual patient data in tables or graphs were reviewed. Clinical benefits tended to decline when the haloperidol blood concentration was increased above 26 ng/ml. Our data support the existence of a therapeutic window between 4 and 26 ng/ml for haloperidol in the treatment of schizophrenic, schizoaffective and schizophreniform disorders.

Serum Haloperidol Levels in Older Psychotic Patients

The authors measured serum levels of haloperidol (HL) in outpatients ages 45-83 years with psychosis treated with HL for at least 1 month. Blood was collected from 32 patients with either schizophrenia (n = 23) or Alzheimer's disease (AD) (n = 9). HL daily dose was greater in patients with schizophrenia (median age, 59) than in AD patients (median age, 80) (P < 0.0005), but no significant group differences in HL serum concentrations were observed. In the total sample, age correlated negatively with HL dose (P < 0.001) and positively with the ratio of serum HL level/dose (P < 0.05). The ratio of HL level/dose was higher in the elderly AD patients than in younger subjects with schizophrenia (P < 0.005). Serum HL levels were much lower than those reported in younger schizophrenia patients, but comparable to those reported in elderly patients with AD. Aging-related and disease-associated pharmacokinetic and pharmacodynamic changes may reduce the need for higher neuroleptic doses as well as higher blood levels in older patients.

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.

Correlation of clinical response (PANSS) and plasma levels of haloperidol and reduced haloperidol in schizophrenia

1. The authors attempted to correlate plasma concentrations in H/rH and clinical efficacy from 8 schizophrenic patients (DSM IIIR) on H. 2. No significant correlations were found between H, rH plasma levels and positive and negative subscale for each patient. 3. The authors observed an opposite evolution concerning the mean results between plasma concentrations and PANSS total score.

Neuroleptic effects on serine and glycine metabolism

The concentrations of serine and glycine and the activity of serine hydroxymethyltransferase (SHMT) are abnormal in plasma and brains of schizophrenics. To further elucidate the possible role of neuroleptics on the metabolism of serine and glycine and the activity of SHMT, we studied the plasma of controls and schizophrenics on and off medications, the brains of rats treated with haloperidol, and the activity of purified SHMT in the presence or absence of haloperidol and fluphenazine. Plasmas of neuroleptic-treated schizophrenics had nonsignificantly lower concentrations of serine and glycine. Brains of haloperidol-treated rats had significantly lower concentrations of serine and glycine. At therapeutic levels haloperidol and fluphenazine did not inhibit the activity of purified SHMT. The serine-glycine lowering effects of haloperidol and neuroleptics are discussed in the context of a possible neuroprotective potential of neuroleptics in schizophrenia.

Enhanced haloperidol-induced prolactin stimulation with chronic neuroleptic treatment in the rat

Animals were treated either acutely, or chronically for 21 days, with a low dose (0.1 mg/kg) of haloperidol, then sacrificed to obtain trunk blood for radioimmunoassay of prolactin (PRL) level. PRL concentrations on day 21 of chronic treatment were greater than two-fold those produced by acute neuroleptic. Challenge with apomorphine to rats withdrawn for 48 hours revealed similar PRL reductions as a group withdrawn from chronic vehicle injections.

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.

A fixed dose study of the plasma concentration and clinical effects of thioridazine and its major metabolites

Fifty-three patients in an acute episode or exacerbation of psychosis were given thioridazine 200 or 400 mg daily for 2 weeks. Thioridazine and its active metabolites, mesoridazine and sulforidazine, were estimated in plasma by high performance liquid chromatography (HPLC) and radioreceptor assay (RRA). One week after institution of treatment, plasma concentrations of drug were stable in the morning 12h after dosing. Drug levels varied widely between patients, but in all patients the relative level of thioridazine to mesoridazine was about one half and thioridazine to sulforidazine was about two fold. Estimates of neuroleptic activity by RRA and the weighted sum of thioridazine, mesoridazine and sulforidazine by HPLC were very similar. Plasma concentration of parent compound, metabolites, or the sum of active substances as estimated by HPLC or RRA, showed only modest correlations (rs = 0.10-0.22, all NS) to the degree of improvement as measured by change on the Brief Psychiatric Rating Scale. Significant correlations were observed between plasma concentrations of drug and side effects, including dry mouth, blurred vision, or total rating on the Somatic Symptoms Scale. Even patients receiving the lowest dose and achieving the lowest plasma concentrations of drug showed considerable improvement. There was suggestive evidence that the patients achieving the highest plasma levels of drug did not have the best clinical outcome. These and similar observations from other studies suggest that currently used doses of neuroleptics may be excessive. Optimal drug effects as well as stronger relationships between dose, drug concentration, and clinical therapeutic effects might best be sought at doses below those in common use.

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.

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)