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PubMed1987

Effects of catecholaminergic blockade by haloperidol or propranolol at different stages of the oestrous cycle on ovulation and gonadotrophin levels in the rat.

Rats with a 4-day oestrous cycle were injected with 2.5 mg haloperidol/kg, a dopaminergic blocker, or with 2.0 mg propranolol/kg, a beta 1- and beta 2-receptor blocker, at 13.00 h on oestrus, dioestrous day 1, dioestrous day 2 or pro-oestrus. Animals were autopsied on the next expected day of oestrus. Haloperidol blocked ovulation when injected on oestrus, dioestrous day 1 or pro-oestrus and was less effective when injected on dioestrous day 2. Propranolol caused a decrease in the number of ova shed when injected on dioestrous day 2 or pro-oestrus. Serum concentrations of FSH at oestrus were below the control values in those animals in which ovulation was blocked by haloperidol. No significant changes in serum concentrations of LH were observed. The normal gonadotrophin peak which occurs during the afternoon of pro-oestrus was blocked by administration of haloperidol on oestrus or dioestrous day 1. Administration of gonadotrophin-releasing hormone (GnRH) to haloperidol-treated animals on oestrus or dioestrous day 1 did not restore ovulation or increase serum FSH levels. When the same dose of GnRH was given to rats treated with haloperidol on pro-oestrus, they all ovulated and their FSH levels rose normally. Treatment with both FSH and LH of rats given haloperidol at oestrus restored ovulation in 50% of the animals, whereas it was ineffective in animals treated on dioestrous day 1. Fifty per cent of the animals treated with haloperidol on oestrus or dioestrous day 1 ovulated when oestradiol benzoate was injected on dioestrous day 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1998

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.

Acute Disease↗

PubMed1992

Neurochemical and motor effects of high dose haloperidol treatment: exacerbation by tryptophan supplementation.

The neurochemical and motor effects of a high dose (25 mg/kg) of haloperidol were assessed in male Sprague-Dawley rats. In Experiment 1, this high dose of haloperidol caused dramatic increases in striatal dopaminergic and serotonergic turnover that only returned to control levels 100 hr after injection. In the second experiment, the same dose of haloperidol was administered twice over a 3-week interval in the presence or absence of a dietary tryptophan supplement added to the drinking water. Rats were assessed for disruption of locomotor behavior (using the rotorod) as well as the occurrence of spontaneous (dyskinetic-like) chewing and head twitching. It was observed that haloperidol impaired rotorod performance in a manner that paralleled the time course of the neurochemical changes in Experiment 1. In addition, the tryptophan (consumed at an average of 157 mg/kg/day) exacerbated the deficit in rotorod performance in haloperidol-treated rats after the first, but not after the second, haloperidol injection. Finally, the combination of haloperidol plus tryptophan was found to cause a long-lasting increase in spontaneous chewing movements that lasted 56 days after the first injection. These observations are interpreted in the context of tryptophan supplementation to antipsychotic therapy.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1997

Extrapyramidal symptoms and tolerability of olanzapine versus haloperidol in the acute treatment of schizophrenia.

BACKGROUND: A relative lack of extrapyramidal symptoms (EPS, i.e., the syndromes of dystonia, parkinsonism, akathisia, dyskinesia) is one criterion used to determine whether an antipsychotic is "atypical." The extrapyramidal symptom profiles of the novel antipsychotic olanzapine and the conventional antipsychotic haloperidol were compared in a population of 2606 patients from three well-controlled prospective clinical trials. METHOD: Extrapyramidal symptom data were analyzed for 1796 patients treated with olanzapine (5 to 20 mg/day) and 810 patients treated with haloperidol (5 to 20 mg/day) for up to 6 weeks of therapy. Patients were monitored weekly by three methods of extrapyramidal symptom assessment: (1) detection of extrapyramidal adverse events (signs and symptoms) by casual observation, nonprobing inquiry, and spontaneous report; (2) objective rating scale scores: and (3) use of concomitant anticholinergic medications. Emergence of EPS was assessed by (1) analysis of the incidence of extrapyramidal syndrome categories based on adverse events, (2) the incidence of extrapyramidal syndromes based on categorical analysis of rating scale scores, (3) analysis of mean maximum change in rating scale scores, and (4) categorical analysis of anticholinergic medication use. Outcome of EPS was assessed by (1) analysis of mean change in rating scale scores at endpoint and (2) mean anticholinergic use at endpoint. RESULTS: Olanzapine was statistically significantly (p = .014, p < .001) superior to haloperidol in all four analyses related to emergence of EPS and in the two analyses related to outcome. Furthermore, during acute treatment, statistically significantly fewer patients treated with olanzapine (0.3%) discontinued the study because of any extrapyramidal adverse event than patients treated with haloperidol (2.7%, p < .001). CONCLUSION: Olanzapine exhibited a statistically significantly lower extrapyramidal symptom profile than the conventional antipsychotic haloperidol at comparably effective antipsychotic doses. The lower extrapyramidal symptom profile with olanzapine was evident despite statistically significantly more frequent use of anticholinergic drugs among haloperidol-treated patients. Fewer olanzapine-treated than haloperidol-treated patients discontinued because of EPS, suggesting that olanzapine should contribute to better compliance with longer term maintenance treatment, with minimal anticholinergic-associated events.

Adult↗

PubMed2001

Factors influencing acute weight change in patients with schizophrenia treated with olanzapine, haloperidol, or risperidone.

OBJECTIVE: Clinical factors predicting weight change in patients with schizophrenia and related disorders during acute treatment with the antipsychotic drugs olanzapine, risperidone, and haloperidol were sought through retrospective analyses. METHOD: Six-week body-weight data from 2 trials, study 1 comparing olanzapine and haloperidol (N = 1,369) and study 2 olanzapine and risperidone (N = 268), were analyzed. Effects of 8 clinically relevant covariates--therapy, clinical outcome (Brief Psychiatric Rating Scale), baseline body mass index (BBMI), increased appetite, age, gender, race, and dose--on weight were compared. RESULTS: In study 1, olanzapine (vs. haloperidol) therapy, better clinical outcome, lower BBMI, and nonwhite race significantly affected weight gain. Effects of increased appetite and male gender on weight gain were significant for olanzapine but not for haloperidol. In study 2, better clinical outcome, lower BBMI, and younger age significantly affected weight gain. Increased appetite was more frequent during olanzapine treatment than during haloperidol, but not significantly different from risperidone. Significant differences in effect on weight change were found between olanzapine and haloperidol but not between olanzapine and risperidone. No evidence was found that lower antipsychotic drug doses were associated with lower weight gain. CONCLUSION: This report identifies predictive factors of acute weight change in patients with schizophrenia. Similar factors across antipsychotic drugs in predicting greater weight gain included better clinical outcome, low BBMI, and nonwhite race. Factors differing between conventional (haloperidol) and atypical (olanzapine) agents included increased appetite and gender. Choice of atypical antipsychotic drug (olanzapine vs. risperidone) was of minor importance with regard to influence on acute weight gain.

Adult↗

PubMed1998

Behavioural alterations in rats induced by single prenatal exposure of haloperidol.

Haloperidol (50 mg/kg, i.p.) treatment was given once to two different groups of pregnant Charles Foster rats on gestational day 9 and 14, these being respectively the critical periods of neural morphogenesis and rapid neural cell proliferation in this species. Pregnant control rats were similarly treated with equal volume of vehicle. The pups born were subjected to open-field exploratory behaviour and elevated plus-maze behaviour tests of anxiety and learned helplessness test of depression at 9 weeks of age. The results indicate that prenatal haloperidol treatment on gestational day 14 induces a significant increase in open-field ambulation and faecal droppings whereas haloperidol treatment on gestational day 9 caused significantly decreased rearing and unaltered ambulation in rat offsprings. Rat offsprings treated with haloperidol on gestational day 9 and 14 also displayed significant anxiogenic behaviour pattern on elevated plus-maze. Significantly increased number of escape failures were observed in learned helplessness tests indicating presence of depression in haloperidol treated rat offsprings. These behavioural alterations were found to be more marked in rat offsprings treated with haloperidol on gestational day 14. The results suggest that prenatal single exposure of high dose of haloperidol during critical period of neural cell proliferation leaves a lasting imprint on offsprings resulting in abnormal emotional state.

Animals↗

PubMed1999

Pharmacokinetic and pharmacodynamic interactions among haloperidol, carteolol hydrochloride and biperiden hydrochloride.

A beta-adrenoceptor blocker and an anticholinergic agent are often prescribed concomitantly for the treatment of neuroleptic-induced akathisia. The aim of this study was to investigate possible pharmacokinetic interactions of neuroleptic haloperidol with the beta-blocker carteolol and the anticholinergic biperiden. In a 5-step, open-labeled, oral single-dose study, eight healthy male volunteers received 2 mg haloperidol, 10 mg carteolol hydrochloride, and 2 mg biperiden hydrochloride: first each drug alone, then a combination of haloperidol and carteolol, and then all three drugs concurrently. Serum concentrations of haloperidol, carteolol, and biperiden were determined up to 24 hr postdosing, and a safety evaluation was conducted throughout the study. Carteolol increased the area under the haloperidol serum concentration-time curve (AUC0-t) 1.4-fold (P = 0.0014) and decreased the serum clearance of haloperidol up to 67% (P = 0.0127). Biperiden reduced the serum haloperidol concentrations increased by the administration of carteolol. No significant changes of the serum pharmacokinetics of carteolol and biperiden were found as a result of any drug combinations. Adverse events of the central nervous system such as sleepiness and changes in pupil size were observed, but all were mild with clinical insignificance.

Adrenergic beta-Antagonists↗

PubMed1979

The time course of the behavioral effects of amphetamine and their reversal by haloperidol in a primate species.

A group of six marmosets was administered amphetamine (Phase I), amphetamine plus haloperidol (Phase II), and then amphetamine alone (Phase III) over consecutive periods of 27, 51, and 33 days after which drug treatment was terminated (Phase IV). The animals' behavior was monitored during these periods and during a predrug treatment control period. Five mutually exclusive categories of behavior were assessed during the experiment. Social contact between animals was significantly suppressed and inactivity was increased throughout Phases I--III but both measures returned to normal values during Phase IV. Locomotion was significantly decreased towards the end of Phase I and initially during Phase II. Rapid head movements (termed checking) were significantly increased at the beginning of Phase I and again when the haloperidol was withdrawn at the beginning of Phase III. Towards the end of Phase I the animals developed destructive self-grooming habits. The time course of the effects of amphetamine and haloperidol on the different behavioral categories suggests that different mechanisms may be involved in each case. Viewed as a model of schizophrenia, the time course of haloperidol in reversing amphetamine-induced suppression of locomotion most closely resembles the time course of the antipsychotic effect of neuroleptics in man. Some effects of amphetamine (e.g., suppression of social interaction) are not reversed by haloperidol, and some effects of withdrawal of haloperidol (e.g., precipitation of checking movements not present when haloperidol was commenced) do not have an obvious counterpart in the clinical situation.

Amphetamine↗

PubMed2002

Differences in the effects of haloperidol and clozapine on brain serotonin and dopamine metabolism and on tests related to extrapyramidal functions in rats.

BACKGROUND: An important goal of current neuroleptic research is to develop antipsychotic compounds with a low incidence of extrapyramidal side effects (EPS). Clozapine, the first of the atypical antipsychotics to be proven effective in treatment-resistant schizophrenia, is reported to produce less EPS than typical neuroleptics, such as haloperidol. MATERIAL/METHODS: The present study compares the neurochemical profiles of clozapine and haloperidol in rats. Animals injected (i.p.) with haloperidol or clozapine were sacrificed 1h later to collect brain samples. Neurochemical estimations were carried out by HPLC-EC. RESULTS: Administration of haloperidol at doses of 1.0, 2.5 and 5.0 mg/kg increased the concentration of homovanillic acid (HVA), a metabolite of dopamine (DA), in the striatum and rest of the brain. Clozapine-injected rats (2.5, 5.0 and 10.0 mg/kg) showed smaller increases in the striatum, but not in the rest of the brain. Dihydroxyphenylacetic acid (DOPAC), another DA metabolite not affected by haloperidol, increased in the striatum and decreased in the rest of the brain of clozapine-injected rats. 5-Hydroxyindoleacetic acid, the predominant metabolite of serotonin, increased with haloperidol and decreased with clozapine. A high dose of haloperidol (5.0 mg/kg) increased DA and 5-HT, while an equivalent does of clozapine (10.0 mg/kg) decreased levels in the rest of the brain. The effects of both drugs on the HVA/5-HIAA and DOPAC/5-HIAA ratios were also different. CONCLUSIONS: The differing activities of the two drugs at DA and serotonin receptors implies an important role for serotonin in treatment-resistant schizophrenia and a lower incidence of EPS.

Animals↗

PubMed2004

Effectiveness of antipsychotic treatments for schizophrenia: interim 6-month analysis from a prospective observational study (IC-SOHO) comparing olanzapine, quetiapine, risperidone, and haloperidol.

BACKGROUND: The Intercontinental Schizophrenia Outpatient Health Outcomes (IC-SOHO) study was designed to provide information regarding use and outcome of antipsychotic treatments in a large, diverse population in real practice settings. METHOD: Outpatients with schizophrenia (ICD-10 or DSM-IV) who initiated or changed to a new antipsychotic entered this 3-year, naturalistic, prospective observational study. Four monotherapy treatment groups were defined according to the antipsychotic prescribed at baseline, namely olanzapine, risperidone, quetiapine, and haloperidol. Efficacy was assessed using the Clinical Global Impressions-Severity of Illness rating scale (CGI-S), inclusive of subscales for positive, negative, depressive, and cognitive symptoms. Tolerability was assessed by adverse event questionnaires and weight measurements. Six-month findings are described. RESULTS: At baseline, 5833 participants were prescribed monotherapy and the mean severity of illness was moderate to marked (CGI-S). At 6 months, olanzapine resulted in significantly greater improvements in overall, positive, negative, depressive, and cognitive symptoms compared with quetiapine, risperidone or haloperidol (p <.001). Improvements in overall, negative, and cognitive symptoms were significantly higher for risperidone compared with haloperidol (p <.001), whereas improvements across all symptoms were comparable for quetiapine and haloperidol. Extra-pyramidal symptoms and tardive dyskinesia decreased compared with baseline in the olanzapine, quetiapine, and risperidone groups but increased in the haloperidol group (p <.001, likelihood of extrapyramidal symptoms with haloperidol compared with olanzapine, quetiapine, or risperidone). Sexual function adverse events were most prominent in the haloperidol and risperidone treatment groups. Weight change was significantly greater for olanzapine compared with the other antipsychotics (p <.001). CONCLUSION: Our results support the previously reported positive impact of atypical antipsychotics, particularly olanzapine, in patients with schizophrenia.

Adult↗

PubMed1991

Factors related to haloperidol response and dyskinesias in autistic children.

A secondary analysis of data pooled from three studies (Anderson et al. 1984, 1989; Campbell et al. 1978) was performed to identify variables predictive of haloperidol response in 125 autistic children, with ages ranging from 2.3 to 8.2 years. Mean behavioral improvement was greater under haloperidol treatment conditions than under placebo. Higher intelligence quotient (IQ) was predictive of reduction in behavioral symptoms under general conditions of haloperidol or placebo treatment, while older children were found to respond favorably to haloperidol itself. Under both haloperidol and placebo conditions, there was also a tendency for greater reduction in symptoms, in terms of raw score and percent change, for those with greater initial severity of illness. Results for initial severity of illness as a predictor of improvement generalized across a wide variety of behavior not specific to autism (e.g., hyperactivity and temper outbursts). However, mean behavioral improvement and its prediction with demographics for individuals tended to be more specific to symptoms related to autism per se. Reduction in symptoms during short-term haloperidol treatment was not found to be related to whether or not children developed dyskinesias in subsequent long-term haloperidol administration.

Autistic Disorder↗

PubMed1990

Effects of chronic haloperidol on vitamin E levels and monoamine metabolism in rats fed normal and vitamin E deficient diets.

Experiments were conducted to study the effects of chronic haloperidol treatment on brain catechols and indoles in rats fed vitamin E deficient diets. Rats were fed basal diet or vitamin E deficient diet and injected with saline or haloperidol (1 mg/kg/day x 28 days i.p.). Tissue levels of catechols, indoles and vitamin E were measured using HPLC-EC techniques. Chronic haloperidol reduced striatal vitamin E levels. Activity in the striatal dopaminergic systems was also reduced, as, shown by reduced 3,4-dihydrophenylanine (DOPA), homovanillic acid (HVA), 3-methoxytyramine (3-MT), and dopamine (DA) levels. In addition, serotonergic activity was reduced, as indicated by lowered 5-hydroxytryptophan (5-HTP), 5-hydroxyindoleacetic acid (5-HIAA), and 5-hydroxytryptamine (5-HT) levels. In the substantia nigra, only 5-HIAA levels were reduced by treatment with haloperidol. These effects of haloperidol on monoamine metabolism were noted in both the vitamin E deficient and basal diet treated rats. However, vitamin E deficiency alone resulted in reduced DOPA and dopamine in the striatum. The vitamin E deficient diets resulted in markedly lowered vitamin E levels in the striatum and substantia nigra. All of these effects were more profound in rats that had been maintained on a vitamin E deficient diet for 7 weeks than those that were so treated for 5 weeks. These results suggest that alterations in dopamine metabolism and endogenous antioxidant systems may interact. Neuroleptics such as haloperidol that acutely accelerate dopamine synthesis and metabolism may cause peroxidative stress as indicated by depletions of vitamin E. Such depletions are capable of reducing dopamine levels and synthesis. The possibility that this and the effect of chronic haloperidol are mediated by peroxidative damage to dopamine neurons must be considered.

Animals↗

PubMed1986

Haloperidol binding to monoclonal antibodies: conformational analysis and relationships to D-2 receptor binding.

A library of 22 monoclonal antibodies to the D-2 dopaminergic receptor antagonist haloperidol has been developed by immunizing BALB/c mice with two conformationally distinct immunogens. The two immunogens were prepared by coupling haloperidol to bovine serum albumin through the tertiary alcohol at the 4-position of the piperidine ring with a succinic acid linkage and by coupling to bovine serum albumin through the ketone group of the butyrophenone with a carboxymethyl oxime linkage. Seventeen monoclonal antibodies displayed specific, saturable, high affinity binding of [3H]haloperidol which could be inhibited by a variety of neuroleptic drugs. Three monoclonal antibodies raised against the succinic acid conjugate and two monoclonal antibodies raised against the oxime conjugate were selected for detailed analysis of the molecular characteristics of binding specificity and for relationships to bovine striatal D-2 dopaminergic receptor binding. The monoclonal antibody with highest affinity for haloperidol, 185(2)-1 (raised against the succinic acid conjugate and herein referred to as mAb A), had a Kd of 3.3 (+/- 0.06) nM and primarily recognized chemical determinants in the butyrophenone ring (ring 1) and side chain. Inhibition of [3H]haloperidol binding to mAb A by 16 unlabeled haloperidol analogs displayed a good correlation [r = 0.82, n = 16, m = 1.06(+/- 0.38)] with D-2 receptor binding affinity, suggesting that the parts of the D-2 receptor combining site which recognize butyrophenone antagonists may have molecular characteristics which are similar to those of the monoclonal antibody. Other dopaminergic ligands such as dopamine and the D-1 antagonist SCH-23390 were not recognized by monoclonal antibodies raised against the succinic acid conjugate. Monoclonal antibodies raised against the oxime conjugate such as 258(2)-1 (herein referred to as mAb D) primarily recognized chemical determinants in ring 2 and the tertiary amino group of the piperidine ring. Although the D-2 receptor and mAb D both prefer electron-withdrawing substituents in the para position of ring 2, the antibody was more sensitive than the receptor to changes and displayed affinities that were much lower for substituents attached to the p-chlorophenyl ring (ring 2), which were electron donating. In addition, dopamine was able to completely displace 4 nM [3H]haloperidol from mAb D at a concentration of 6 mM.

Animals↗

PubMed1987

Review of haloperidol blood level and clinical response: looking through the window.

The studies of relationship between haloperidol plasma levels and clinical response in schizophrenia have yielded variable results. A therapeutic window for haloperidol may exist, but the evidence for it is inconsistent. Future studies of this problem using larger patient samples would permit the investigation of interactions between the clinical predictors and the haloperidol plasma levels in the determination of clinical outcome. Although the reduced haloperidol in plasma as well as the red blood cell levels of haloperidol and reduced haloperidol or ratios of the metabolite to parent compound may also be related to clinical outcome, the evidence for this relationship is very tentative. More research is needed before routine clinical monitoring of haloperidol blood levels can be recommended.

Dose-Response Relationship, Drug↗

PubMed1986

Pharmacology, pharmacokinetics and clinical development of haloperidol decanoate.

The absorption mechanism of haloperidol decanoate from the intramuscular depot was studied in dogs. Haloperidol, a pharmacologically active molecule characterised by selective dopamine antagonism, was detectable in plasma within one hour after dosing. Peak plasma levels were obtained within three to seven days. After single and repeated doses of haloperidol decanoate, plasma levels were found to be dose related. Human pharmacokinetics in schizophrenic patients were studied by giving four-weekly deep intramuscular injections of haloperidol decanoate at doses equivalent to the patients' previous antipsychotic medication. Within each interval between doses, haloperidol plasma levels were maximal within the first week after each dose, decaying with an average half-life of three weeks. Steady-state was reached within three months giving therapeutic plasma levels in the same range as those found during oral treatment with haloperidol. Open and double-blind clinical trials have demonstrated the clinical efficacy of haloperidol decanoate given four-weekly by deep intramuscular injection over a dose range from 50 to 300 mg, principally in schizophrenic patients. Low incidences of extrapyramidal side effects were noted, often allowing a reduction of antiparkinsonian medication required through previous antipsychotic treatment.

Animals↗

PubMed1987

Decreased extrapyramidal symptoms with intravenous haloperidol.

In a preliminary, prospective study, the intensity of extrapyramidal symptoms was rated in four patients receiving intravenous haloperidol and six patients receiving oral haloperidol. The raters were blind to the route of administration. In this pilot study, the first systematic evaluation of intravenous haloperidol and extrapyramidal symptoms, the patients receiving intravenous haloperidol experienced significantly (p less than .01) less intense extrapyramidal symptoms than did the patients receiving oral haloperidol. The literature on intravenous haloperidol is briefly reviewed, and possible explanations of the lower intensity of extrapyramidal symptoms with intravenous haloperidol in the patients studied are discussed.

Administration, Oral↗

PubMed1983

Neuroleptic binding sites: specific labeling in mice with [18F]haloperidol, a potential tracer for positron emission tomography.

Haloperidol labeled with fluorine-18 (T 1/2 = 110 min, positron emission 97%), prepared yielding .04 Ci/millimole by the Balz-Schiemann reaction, was evaluated in a murine model as a potential radiotracer for noninvasive determination, by positron-emission tomography, of regional concentrations of brain dopamine receptors in patients. As the haloperidol dose in mice was increased from 0.01 to 1000 micrograms/kg, the relative concentration of [18F]haloperidol (microCi per g specimen/microCi per g of body mass), at one hour after injection decreased from 30 to 1.0 in the striatum and from 8.0 to 1.0 in the cerebellum. The striatal radioactivity, plotted as relative concentration against log of dose, decreased sigmoidally, presumably reflecting competition between labeled and unlabeled haloperidol for a single class of accessible binding sites. Because the cerebellum is relatively deficient in dopamine receptors, the observed decrease in cerebellar radioactivity may reflect a saturable component of haloperidol transport into brain. The high brain concentrations and the unexpectedly high striatum-to-cerebellum concentration ratios (greater than 4 at haloperidol doses less than or equal to 1 microgram/kg) suggest that [18F]haloperidol warrants further investigation as a potential radiotracer for dopamine receptors.

Animals↗

PubMed1984

Increase of striatal Met5-enkephalin-Arg6-Phe7 (YGGFMRF) content elicited by long-term treatment with haloperidol.

In rats, daily doses of haloperidol repeated for various time periods increase striatal Met5-enkephalin-Arg6-Phe7 (YGGFMRF) immunoreactivity in a time- and dose-dependent manner. This increase occurred also in other dopamine-rich brain areas. After intraventricular captopril (0.5 mg), the accumulation rate of immunoreactive YGGFMRF was greater in haloperidol- than in saline-injected rats. Intraventricular captopril inhibits the YGGFMRF degradation; hence the greater accumulation rate of YGGFMRF caused by captopril in haloperidol-treated rats suggests that this drug increases the YGGFMRF biosynthesis. A slower rate of YGGFMRF release in haloperidol-treated rats can be excluded as a cause for the drug-induced increase in striatal content of this peptide because the release rates of YGGFMRF elicited by K+ were similar in striatal slices of haloperidol- and saline-treated rats. The similarities between the accumulation rate of immunoreactive YGGFMRF and of Met5-enkephalin induced by haloperidol suggest that haloperidol increases the biosynthesis of the specific messenger RNA for preproenkephalin, an opioid peptide precursor, which contains one copy of YGGFMRF and several copies of Met5-enkephalin.

Animals↗