Serum and CSF levels of haloperidol by radioimmunoassay and radioreceptor assay during high-dose therapy of resistant schizophrenic patients

Clinical Pharmacokinetics and Pharmacodynamics of Drugs in the Central Nervous System

Despite contributing significantly to the burden of global disease, the translation of new treatment strategies for diseases of the central nervous system (CNS) from animals to humans remains challenging, with a high attrition rate in the development of CNS drugs. The failure of clinical trials for CNS therapies can be partially explained by factors related to pharmacokinetics/pharmacodynamics (PK/PD), such as lack of efficacy or improper selection of the initial dosage. A focused assessment is needed for CNS-acting drugs in first-in-human studies to identify the differences in PK/PD from animal models, as well as to choose the appropriate dose. In this review, we summarize the available literature from human studies on the PK and PD in brain tissue, cerebrospinal fluid, and interstitial fluid for drugs used in the treatment of psychosis, Alzheimer's disease and neuro-HIV, and address critical questions in the field. We also explore newer methods to characterize PK/PD relationships that may lead to more efficient dose selection in CNS drug development.

Psychotropic drugs in mothers' milk: a comprehensive review of assay methods, pharmacokinetics and of safety of breast-feeding

Many mentally ill women want to breast-feed their babies but, if they are taking psychotropic drugs, there is very little systematic data upon which to base decisions about whether or not it is safe to do so. We therefore attempt to provide a comprehensive and critical summary of existing case reports and of studies of breast-feeding in relation to commonly used psychotropic drugs. The literature review focuses on the following drugs: antidepressants: tricyclics and serotonin selective reuptake inhibitors (SSRIs); antipsychotic drugs: chlorpromazine, perphenazine, haloperidol and clozapine; mood stabilizers: lithium and carbamazepine; and benzodiazepines. The research literature consists mainly of single case reports and there have been very few attempts at controlled, longitudinal investigations. Findings are often difficult to compare because of differences in methods or because of lack of key information. Most data are available about the tricyclic antidepressants but even here we have found that the reports cover only a grand total of 66 mother-infant pairs. Dilemmas about whether or not to contraindicate breast-feeding arise most commonly in relation to postnatal depression. The findings to date suggest that provided that infants are healthy at the outset it is likely that the benefits of breast-feeding will outweigh potential hazards if their mothers are taking established tricyclic drugs at recommended dose levels. Much less is known about risks associated with SSRI antidepressants or about antipsychotic drugs such as phenothiazines and butyrophenones or mood stabilizers such as carbamazepine, all of which enter breast-milk. Safeguards are suggested for future single case studies, which, as they accumulate, will provide a platform for mounting controlled prospective studies properly to test for any acute toxic effects and for possible long-term adverse effects of such drugs on infants' development. Appendix 1 is a review of assay methods. Appendix 2 examines pharmacokinetic factors in newborn preterm and sick infants with special reference to contraindications to breast-feeding. Appendix 3 is a review of methods for assessing infant health and development.

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.

Neuroleptic dosing in chronic schizophrenia: a 10-year follow-up

OBJECTIVE

To evaluate neuroleptic dosing patterns in individuals with schizophrenia over a 10-year interval.

METHOD

Changes in neuroleptic dosing between 1980 and 1990 were followed in 65 patients with a diagnosis of chronic schizophrenia.

RESULTS

According to more recent dosing guidelines, doses were already high at the time of initial evaluation, yet overall they continued to increase during the next decade of treatment for both males and females. Patients were almost equally divided, however, by those who underwent an increase (n = 33) and those whose dose remained stable (n = 4) or was decreased (n = 28).

CONCLUSION

A considerable number of patients with schizophrenia appear to receive progressively higher neuroleptic doses over the course of their illness, despite a lack of empirical data to support such an approach. Results are discussed in terms of current dosing recommendations and factors influencing dose changes.

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.

Study of the clinical utility of radioreceptor assay in outpatients with schizophrenia receiving high doses of neuroleptics

A radioreceptor assay (RRA) was used to determine the neuroleptic plasma levels of 32 outpatients with schizophrenia receiving a high dose of neuroleptics (the equivalent of 18 mg or more of oral haloperidol per day) and undergoing a 50% partial and progressive reduction (ten percent each month for five months) in their medication. Plasma levels of neuroleptics were measured three times: before (T1) and immediately after the 50% reduction (T2) and five months later (T3). A linear correlation was observed between neuroleptic plasma levels obtained by RRA and the neuroleptic doses prescribed at T1 and T3. Furthermore, neuroleptic plasma levels were significantly lower at T3 than at T1. Concurrent evaluations of psychopathology were done using the Brief Psychiatric Rating Scale, and the results indicated that no correlation exists between neuroleptic plasma levels and the total rating scale scores at T1 but a significant correlation was observed at T3.

Chronic treatment with haloperidol modifies the sensitivity of autoreceptors that modulate dopamine release in rat striatum

The effects of apomorphine or sulpiride on electrically evoked dopamine release from striatal slices of rats pretreated with haloperidol were investigated. Chronic haloperidol treatment (1 mg/kg per day for 21 days) significantly reduced electrically evoked dopamine release from striatal slices until 72 h after the last injection. The apomorphine-induced reduction and the sulpiride-induced increase in evoked dopamine release were significantly enhanced by the chronic treatment with haloperidol at 72 h after the last injection. The enhancement of the sulpiride-induced increase in evoked dopamine release was inversely correlated with the dopamine release evoked by the first stimulation in striatal slices from haloperidol-treated (r = -0.85, n = 12, P < 0.01) but not from saline-treated rats. These results suggest that an increase in the sensitivity of dopamine autoreceptors due to chronic treatment with haloperidol could partially account for the reduction in dopamine release from striatal slices of rats.

Alterations in dopamine release from striatal slices of rats after chronic treatment with haloperidol

The effects of chronic treatment with haloperidol on spontaneous and electrically evoked dopamine (DA) release from striatal slices of rats were investigated in vitro. DA was measured by high-performance liquid chromatography coupled to an electrochemical detector. The superfusion with haloperidol caused a dose-dependent (100 nM-100 microM) reduction in the electrically evoked DA release from striatal slices of rats, which was not antagonized by the superfusion with apomorphine. Chronic administration of haloperidol (1 mg/kg per day for 21 days) caused a significant reduction in electrically evoked DA release as well as in spontaneous DA release from striatal slices 24 h after the last injection. Moreover, pretreatment with haloperidol prevented the reduction of the DA release evoked in response to haloperidol superfusion (1 microM). These results indicated that chronic administration of haloperidol reduced DA release from striatal slices of rats, accompanied by tolerance for the inhibitory effect of drug superfusion on evoked DA release.

The measurement of haloperidol and reduced haloperidol in hair as an index of dosage history

1. We report a method for measuring the concentrations of haloperidol (HL) and its major active metabolite, reduced haloperidol (RHL), in human scalp hair. 2. Hair samples were obtained from 59 patients who had been taking HL at fixed daily doses for more than 4 months and whose compliance was good. A morning pre-dose plasma sample was also obtained from 48 of these patients. 3. The concentrations of HL and RHL in hair (ng mg-1 hair) correlated significantly both with the daily dose (micrograms kg-1 body weight) of HL (r = 0.682, P less than 0.001 for HL and r = 0.813, P less than 0.001 for RHL, n = 59) and with the trough concentration (ng ml-1) of the corresponding compound in plasma at steady state (r = 0.558, P less than 0.001 for HL and r = 0.563, P less than 0.001 for RHL, n = 48). The correlation coefficients were slightly higher using the sum of the concentrations of both substances in hair (r = 0.829 for the correlation with daily dose and r = 0.609 for that with trough concentration). 4. Hair from other patients, in whom the dosage of HL had been changed within a few months prior to sampling, was sectioned into 1 cm-long portions successively from the roots and the concentrations of both compounds in each portion were measured. Assuming a growth rate of 1-1.5 cm/month, a history of individual dosage could be deduced in all patients from the distribution of the drug and metabolite along the single hair length.(ABSTRACT TRUNCATED AT 250 WORDS)

Human scalp hair as evidence of individual dosage history of haloperidol: a possible linkage of haloperidol excretion into hair with hair pigment

We report a method for determining haloperidol concentration in human scalp hair and discuss a possible linkage of haloperidol excretion into hair with the hair pigment melanin. First, an animal study was conducted to support the idea that hair contains amounts of haloperidol corresponding to the doses given and pigmented hair contains much more drug than does unpigmented hair. The haloperidol concentration was measured using a radioimmunoassay technique after hairs were dissolved in 2.5 N NaOH solution and the drug extracted. Pigmented and albino rats, whose hair from an area on the back had been removed beforehand by plucking, were administered either 1, 3, or 10 mg of haloperidol (i.p.) per kg body weight every day for 3 weeks. At the end of the administration period hair which had newly grown on the denuded area was plucked and collected. In each of the two groups classified by hair color the drug levels in the hair correlated with the doses given; however, the concentrations in the hair from the albino rats were much lower than those in the hair from the pigmented rats (which was less than 8.5%). Second, black and white hair was collected from each of seven human subjects with grizzled hair, who were receiving or had been administered haloperidol at fixed daily doses for more than 1 month, and the concentration of haloperidol in each type of hair was measured. In the same subject the concentration in the white hair was found to be much lower than that in the black (less than 10%).(ABSTRACT TRUNCATED AT 250 WORDS)

Predictors of response to high dose antipsychotics in chronic schizophrenics

Significant numbers of chronic schizophrenic patients do not experience sufficient symptom relief from usual doses of antipsychotic medication. Clinicians must decide if high doses of antipsychotics should be tried. In this study baseline symptoms, drug levels, and the symptomatic effects of an acute stimulant challenge were examined before 14 subjects received a 50% increase in their antipsychotic dosing. The group as a whole did not improve. Several individuals with lower drug levels, high baseline hallucinations, and stimulant-induced improvement in hallucinations improved mildly after 3 weeks on the higher antipsychotic dose.

Clinical response and plasma haloperidol levels in chronic and subchronic schizophrenia

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

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.

Human scalp hair as evidence of individual dosage history of haloperidol: method and retrospective study

Hair samples and morning pre-dose plasma were collected from 40 patients who had received fixed daily doses of haloperidol for more than four months and whose compliance was good. After washing, 1 to 2 cm-long portions nearest to the roots of 2 to 3 strands of hair were completely dissolved in 2.5N NaOH. Haloperidol in that sample or alkalinised plasma was extracted and measured by RIA. Haloperidol concentrations in hair correlated well both with the trough concentration in plasma at steady-state (r = 0.772, n = 39) and with the daily dose (r = 0.555, n = 40). Another keratinized tissue, nail, was also collected from 20 of the 40 patients and the haloperidol level was compared with that in hair. The former was only about 4.3% of the latter and was significantly correlated only with the daily dose (r = 0.525, n = 20). Hair from 10 other patients in whom the dosage of haloperidol had been changed within a few months prior to sampling the hair was cut into 0.5 or 1 cm-long portions from the roots and the drug concentration in each portion was measured. If hairs were assumed to grow at 1 cm/month, a history of individual dosage could be deduced in 9 of the 10 patients from the distribution of drug level along the length of the hair. The results suggest that human scalp hair could serve as a useful tool for monitoring individual dosage history over several months, or in demonstrating exposure or non-exposure of a patient to a drug.

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.

Serum haloperidol levels and clinical response in chronic, treatment-resistant schizophrenic patients

Eleven chronic treatment-resistant schizophrenic in-patients were treated with haloperidol (HPL) or placebo with a fixed ascending dose schedule for 20 weeks. Seven patients relapsed and were withdrawn and five of these re-entered, single-blind, on known active treatment. Two weekly clinical ratings and weekly serum HPL levels were carried out throughout the study. More patients on placebo dropped out and at an earlier stage than those on active treatment but the difference was not statistically significant. Despite wide individual variations in both serum HPL levels and clinical response, these were positively correlated. HPL appeared to be of more value in the prevention of relapse than in symptom reduction. Overall, the clinical response was poor and a 'therapeutic window' could not be demonstrated either for the group as a whole or in any individual patient. There was no additional therapeutic benefit in exceeding serum HPL levels of 20 ng/ml in any of our patients. Since this serum level was achieved by daily doses of 10-40 mg HPL and the relationship between dose and serum level is linear, the use of serum HPL estimations is not likely to be of value in the routine clinical management of treatment-resistant patients.

Dopamine antagonists reduce spontaneous electrical activity in cultured mammalian neurons from ventral mesencephalon

Mammalian neurons from ventral mesencephalon (VM) were grown in primary dissociated cell (PDC) culture. These neurons are predominantly non-dopaminergic. Many of these non-dopaminergic neurons have dopamine agonist and antagonist binding sites. Intracellular recordings were obtained from these neurons. When bathed in phosphate-buffered saline (PBS) solution they generated action potentials spontaneously. However, in the presence of haloperidol dissolved in PBS solution, the percentage of neurons which generated action potentials spontaneously was reduced in a dose-dependent manner (1-10 microM). This response was also obtained with (+) butaclamol (1 microM) but not with (-) butaclamol (1 microM). This neuroleptic inhibition of spontaneously generated action potentials was specific for neurons in PDC cultures of VM since neurons in PDC cultures of spinal cord did not demonstrate this phenomenon.

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.

Haloperidol plasma levels and clinical response in paranoid schizophrenics

The relationship between haloperidol plasma levels, plasma prolactin, and therapeutic efficacy was evaluated in 20 paranoïd schizophrenics in a fixed-dose study for 6 weeks. We found a significant intrapatient cross-correlation of therapeutic efficacy, as measured by decrease in MSS and BPRS rating scales and time-dependent haloperidol and prolactin changes, which were tested at weekly intervals. However, no significant curvilinear relationship was present between steady-state haloperidol plasma levels and MSS and BPRS improvement scores. Our data do not furnish clear-cut evidence in favor of the existence of a therapeutic window for haloperidol plasma levels in paranoïd schizophrenia.

Total and free plasma neuroleptic levels in schizophrenic patients

Nineteen male patients, under 35 years of age, newly admitted with a diagnosis of schizophrenia, were treated with either chlorpromazine or haloperidol at a fixed dosage for 25 days. Both total and free plasma neuroleptic levels were measured using a radioreceptor assay. Clinical response was measured by the Brief Psychiatric Rating Scale (BPRS). On day 25, nonresponders (those with a decrease of less than 8 points on the BPRS) had both total and free plasma neuroleptic levels within the range observed in responders. It is therefore concluded that lack of therapeutic response is generally not due to inadequate plasma drug levels.

Serum effects confound the neuroleptic radioreceptor assay

The neuroleptic radioreceptor assay (NRRA) is used widely to monitor total neuroleptic-like activity (NLA) in patients taking one or more antipsychotic drugs. The original report of Creese and Snyder (1) stated that serum alone caused a small effect on binding which was negligible compared to normal daily variations in the assay. Conversely, in studies with striata from rat or cow brain, we found that sera from healthy, drug free volunteers, when used at 50 microL/1 mL assay volume, caused marked inhibition of binding. Although any sample of serum causes reproducible inhibition with a given preparation of bovine or rat striatal membranes, the effects of various serum samples may differ markedly when several striatal membrane preparations are compared. Moreover, samples taken from people at different times may also vary, although less than the interindividual differences. Despite this variance, the slopes of log-logit plots were equal to 1 either in the presence or absence of serum. Because of the differences in the interaction of individual sera with different membrane preparations, it is difficult to compensate accurately for this serum effect by simply including control serum in the standard curve. Thus, the use of the NRRA as a quantitative tool in the clinical pharmacology of neuroleptics may be limited by this non-specific effect of serum, and this finding may offer one explanation for some of the inconsistencies found in comparing the NRRA with direct analytical methods.

Reduced haloperidol in the post-mortem brains of haloperidol-treated patients

We measured the concentrations of haloperidol and its reduced alcohol metabolite in human post-mortem tissues with high-performance/liquid chromatography using electrochemical detection. Both haloperidol and reduced haloperidol were detected and quantified in the occipital cortex of nine schizophrenic patients with a history of haloperidol treatment, but not in six samples from nontreated subjects. Reduced haloperidol concentrations were below the detection limit of the assay in several tissues of rats and mice even after 10 days of haloperidol treatment. The results suggest that reduced haloperidol is present in the brains of haloperidol-treated patients at slightly higher concentrations than haloperidol itself. Further studies are warranted to establish the possible biological importance of this haloperidol metabolite.

Serum neuroleptic and prolactin levels in schizophrenic patients and clinical response

Following a drug-free placebo period lasting at least 1 week, 10 female and 11 male newly hospitalized schizophrenic patients received chlorpromazine (CPZ) 200 mg/day for 1 week and 400 mg/day the following week. Serum CPZ equivalent (CPZ-E) levels were measured at the end of each week of CPZ treatment with a radioreceptor assay. Chlorpromazine-E levels were significantly higher in females than males, but this finding could be accounted for by differences in body weight. Serum prolactin (PRL) levels were also higher in females than males. After differences in serum CPZ-E level were adjusted for, females still had significantly higher serum PRL levels than males. Serum PRL levels increased between the first and second treatment weeks in females but not in males. Correlations between serum CPZ-E and PRL levels were higher among males than females. Significant improvement for the patient group as a whole was observed during the 2 weeks of treatment, with a strong trend for females to improve more than males. Clinical outcome at this initial period was not predicted by either serum PRL levels or serum CPZ-E levels.

Antiemetic effect of haloperidol in the dog as related to plasma level and dose

A positive and highly significant correlation was found between SC dose, plasma concentration, and antiemetic effect of haloperidol in the dog. To protect dogs from apomorphine-induced emesis, a concentration of 1 ng haloperidol/ml plasma was always sufficient, whereas protection from emesis was never obtained with plasma levels lower than 0.53 ng/ml. The elimination rate of haloperidol from plasma varied from 1.53 to 2.60 among different animals. Thus, the interindividual variability to haloperidol was surprisingly low. Antiemetic effect and plasma elimination of haloperidol were not related to body weight.