Radioimmunoassay of haloperidol in human serum

Schizophrenia: recent advances in LC-MS/MS methods to determine antipsychotic drugs in biological samples

Schizophrenia is one of the most debilitating and costly illnesses worldwide. First-generation antipsychotics such as chlorpromazine and haloperidol succeeded in controlling the positive symptoms of schizophrenia, but had significant extrapyramidal effects that led to the search for new agents and the release of second-generation (or atypical) antipsychotics. These drugs had a lower risk of adverse motor symptoms. Therapeutic drug monitoring has become a useful tool to optimize schizophrenia treatment and HPLC-MS/MS has been considered the primary technique to monitor antipsychotics. This review comprises three sections: schizophrenia pathophysiology and treatment; recent advances in LC-MS/MS methods designed to measure levels of antipsychotics and their metabolites in plasma samples (selectivity, matrix effect and sensitivity); and the importance of therapeutic drug monitoring.

Therapeutic drug monitoring of common antipsychotics

The aim of this review is to provide information for interpreting outcome results from monitoring of antipsychotics in biological samples. A brief overview of the working mechanisms, pharmacological effects, drug interactions, and analytical methods of classical and atypical antipsychotics is given. Nineteen antipsychotics were selected based on their importance in the worldwide market as follows: amisulpride, aripiprazole, asenapine, bromperidol, clozapine, flupenthixol, haloperidol, iloperidone, lurasidone, olanzapine, paliperidone, perphenazine, pimozide, pipamperone, quetiapine, risperidone, sertindole, sulpiride, and zuclopenthixol. A straightforward relationship between administered dose, plasma or serum concentration, clinical outcome, or adverse effects is often lacking. Nowadays, focus lies on therapeutic drug monitoring and individualized therapy to find adequate treatment, to explain treatment failure or nonresponse, and to check patient compliance. However, extensive research in this field is still mandatory.

Simultaneous analysis of haloperidol, its three metabolites and two other butyrophenone-type neuroleptics by high performance liquid chromatography with dual ultraviolet detection

We investigated simultaneous determination of haloperidol (HAL), its three metabolites [reduced HAL (R-HAL), 3-(4-fluorobenzoyl)propionic acid (FBPA) and 4-(4-chlorophenyl)-4-hydroxypiperidine (CPHP)] and two related compounds [spiperone (SPI) and droperidol (DRO)] in phosphate-buffered saline using high-performance liquid chromatography (HPLC) coupled with dual ultraviolet detection (220 and 250 nm). Retention times of HAL, R-HAL, FBPA, CPHP, SPI and DRO were 16.8, 11.8, 10.2, 4.1, 12.6 and 8.3 min, respectively. Their lower limits of detection were 7.5, 14, 4.5, 12, 10 and 20 ng/mL in the same order. The coefficients of variation for their intra- and inter-day assays were less than 7.8 and 9.4%, respectively. Of the other centrally acting drugs, only amoxapine interfered with the peak of DRO. Using our procedure, the binding study of tested compounds to synthetic melanin, human serum albumin and alpha1-acid glycoprotein was performed by determining the unbound concentration to total concentration ratio. These results indicated that simultaneous assay of HAL, R-HAL, FBPA, CPHP, SPI and DRO in phosphate-buffered saline by HPLC equipped with dual ultraviolet detection is simple, sensitive and reproducible. Also, our assay system can be applied to the binding study of these compounds to synthetic melanin, human serum albumin and alpha1-acid glycoprotein.

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.

Simultaneous determination of plasma haloperidol and its metabolite reduced haloperidol by liquid chromatography with electrochemical detection. Plasma levels in schizophrenic patients treated with oral or intramuscular depot haloperidol

A simple and highly sensitive liquid chromatographic method with electrochemical detection for the simultaneous determination of haloperidol and its metabolite reduced haloperidol in human plasma has been developed. The sample preparation for the analysis involves a simple one-step extraction procedure with 10% methylene chloride in pentane. The compounds were separated on a cyano column maintained at a temperature of 40 degrees C and were detected electrochemically by a flow-through analytical cell kept at +0.95 V. The standard curve is linear over the range of 0.1 to 15 ng/ml and the lower limit of quantitation is 0.1 ng/ml for haloperidol and 0.25 ng/ml for reduced haloperidol which is equivalent to approximately 40 pg on column when 1 ml of plasma was used for the analysis. The lower limit of quantitation for reduced haloperidol can be extended to 0.1 ng/ml if 2 ml of plasma is used in the analysis. The coefficient of variation of the determination of plasma levels by this method over the standard curve concentration range was less than 10%. Commonly co-administered drugs and other neuroleptics used in conjunction with haloperidol did not interfere in the determination of either haloperidol or reduced haloperidol. This method has been successfully used for the determination of haloperidol and reduced haloperidol in plasma and their levels in patients treated with various doses oral haloperidol or intramuscular haloperidol decanoate are reported.

Direct radioimmunoassay for haloperidol in human serum

A direct radioimmunoassay for the accurate determination of haloperidol in human serum has been developed. Based on recent information about the metabolism of haloperidol, a new haloperidol hapten, in which a (3-carboxypropionyl)methylamino group was attached as a bridge in the place of fluorine atom, was synthesized and coupled to bovine serum albumin through the bridge to provide a new immunogen. Guinea pigs were used for the immunization. Since the antisera obtained by the new immunogen still cross reacted greater than 10% with reduced haloperidol, the immunological tolerance to reduced haloperidol was induced by administration of a copolymer of D-glutamic acid and D-lysine linked with reduced haloperidol. This gave an antiserum in guinea pigs which was highly specific for unchanged haloperidol with negligible cross reactivity (less than or equal to 1.0%) to any haloperidol metabolites including the newly found ones. With the newly developed antiserum and [3H]haloperidol, serum haloperidol levels can be determined over the concentration range from 0.3 to 20 ng/mL, using 0.1 mL of human serum, without an extraction procedure.

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.

Quantification of reduced haloperidol and haloperidol by radioimmunoassay

A radioimmunoassay for reduced haloperidol and haloperidol has been developed by using a simple derivatization-separation step prior to assay with an antibody cospecific for both compounds. The detection limit of the assay is less than 25 pg and shows no cross reactivity to other metabolites. The intraassay coefficient of variation for reduced haloperidol and haloperidol were 9.0 and 8.2% respectively and the interassay coefficients of variation were 9.0 and 10.6% respectively at 5-10 ng/ml. As many as 30 patient samples can be analyzed for both compounds in a single day.

Determination of benperidol in human plasma by high-performance liquid chromatography

A high-performance liquid chromatographic method for the quantitative determination of benperidol in human plasma using haloperidol as internal standard is described. The method involves liquid-liquid extraction, separation of the substances on a reversed-phase column C18 followed by ultraviolet detection at 254 nm. The mobile phase consists of 32% acetonitrile in 0.05 M potassium dihydrogen phosphate buffer (pH 2.8). The detection limit is 0.5-1.0 ng/ml using 2- or 4-ml plasma samples.

Screening procedure for detecting butyrophenone and bisfluorophenyl neuroleptics in urine using a computerized gas chromatographic-mass spectrometric technique

A method for the identification of butyrophenone and bisfluorophenyl neuroleptics and their predominant basic metabolites in urine after acid hydrolysis is described. The acetylated extract is analysed by computerized gas chromatography-mass spectrometry. An on-line computer allows rapid detection using mass fragmentography with the masses m/e 112, 123, 134, 148, 169, 257, 321 and 189, 191, 223, 233, 235, 245, 287, 297. The identity of positive signals in the reconstructed mass fragmentograms is established by a comparison of the entire mass spectra with those of standards. The mass fragmentograms and the underlying mass spectra are documented.

Haloperidol pharmacokinetics: a preliminary study in rhesus monkeys using a new radioimmunoassay procedure

The development, validation, and application of a new radioimmunoassay for haloperidol in biological fluids is described. The antiserum, raised against N-amino-butyl chlorophenyl piperidine bovine albumin conjugate, could not distinguish between haloperidol and its reduced metabolite, but it could discriminate against chlorophenyl piperidine (cross-reaction 2.6%). The fluorophenyl metabolites of haloperidol were not recognized by the antiserum. Haloperidol determinations were made on less than 100 microliter aliquots of human and rhesus monkey plasma or diluted urine without prior extraction of the sample. The radioimmunoassay was applied to the study of the pharmacokinetics of intravenous haloperidol administration to two male rhesus monkeys. Salient features of the results are as follows. As with man, the plasma concentration versus time curve could be resolved into three compartments, but there were differences in the distribution of haloperidol between the compartments. The apparent volume of distribution for the two monkeys examined was 5.87 L kg-1 and 7.37 L kg-1, considerably smaller than in man, a difference almost entirely due to a much smaller tissue compartment. The biological half-life of 15.97 hr and 7.56 hr was similar to man. The mean hepatic extraction ratio was calculated to be 0.032 and 0.056, and the data suggested that hepatic metabolism of haloperidol may be of lesser importance in rhesus monkey than in man. An insignificant proportion (0.01%) of the administered dose was excreted as haloperidol in the urine.

The effects of haloperidol on the EEG spectrum

A placebo-controlled study with six normal volunteers was carried out using 1 mg haloperidol IM. In some EEG frequency bands, the power density due to haloperidol appeared to increase or decrease depending on the subject. Nevertheless, if the results of the six subjects are taken together, the effects of haloperidol are in agreement with the literature. No correlation was found between plasma concentration of haloperidol and EEG response. Some methodological problems are discussed.

Clinical state, plasma levels of haloperidol and prolactin: a correlation study in chronic schizophrenia

Chronic schizophrenic patients were maintained for six months on a dosage of haloperidol adjusted to give optimum clinical effect. A correlation was found between extrapyramidal symptoms and prolactin levels and also between plasma haloperidol concentration and plasma prolactin levels. Estimation of plasma prolactin would be a reliable measurement of patients' compliance with medication.

Radioimmunoassay of bromperidol and haloperidol in human and canine plasma

In order to check the specificity of a radioimmunological assay for haloperidol and bromperidol reported by Michiels et al. (1) and commercialized by IRE (Fleurus, Belgium), the assay was performed on canine and human plasma samples with and without extraction. After a single dose of bromperidol in dogs, plasma levels obtained with and without extraction were similar. In man the plasma levels for bromperidol after a single administration were markedly lower after extraction. The same was true for haloperidol plasma levels after chronic dosing in man. The findings suggest that the direct radioimmunoassay of haloperidol or bromperidol with the commercialized kit, lacks specificity of humans, possibly because of the presence of one or more polar metabolites.

A gas chromatographic mass spectrometric chemical ionization assay for haloperidol with selected ion monitoring

A new gas chromatographic mass spectrometric chemical ionization assay for haloperidol with selectedion monitoring is presented which provides for better combined selectivity and sensitivity than previous assays. Levels of haloperidol in 2 ml of human plasma were reproducibly measured down to subnanogram levels. Both methane and methane--ammonia chemical ionization spectra are presented for haloperidol and the internal standard trifluperidol.

Variability of prolactin response to intravenous and intramuscular haloperidol in normal adult men

Serum prolactin (PRL) concentrations were monitored in seven normal adult men for 1 h before and 7 h after i.v. and i.m. injection of 0.25 mg and 0.50 mg haloperidol. The magnitude of the PRL response was dose-related but quite variable across subjects. The patterns of PRL secretion over the 7 h post-injection period also varied greatly among the subjects. Differences in serum heloperidol concentrations accounted for 88% of the variability in the magnitude of the PRL response to the 0.5 mg IM haloperidol dose, but only accounted for 60% of the PRL variability following the 0.5 mg IV dose. The pattern of haloperidol disappearance from serum was similar across the seven subjects and thus unrelated to the variable patterns of PRL response.

Rapid and sensitive method for determination of haloperidol in human samples using nitrogen-phosphorus selective detection

A sensitive gas-chromatographic method for quantitative analysis of haloperidol in human plasma is described. The use of nitrogen-phosphorus selective detection reduces the time required for analysis. Azaperone is used as the internal reference standard. The method is suitable for the determination of haloperidol plasma levels in patients treated with doses ranging from 1.2 to 200 mg/day. No interference from drugs needed in the associated antipsychotic therapy has been found. The simplicity, specificity and sensitivity of the method make it suitable for routine analysis of haloperidol plasma levels in psychotic patients undergoing chronic treatment.