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PubMed1983

Prolactin increases the activity of tuberoinfundibular and nigroneostriatal dopamine neurons: prolactin antiserum inhibits the haloperidol-induced increases in dopamine synthesis rates in median eminence and striatum of rats.

The role of PRL in mediating the haloperidol-induced increase in tuberoinfundibular dopamine synthesis rate was assessed by studying the effects of administration of PRL antiserum. Antiserum to PRL generated in rabbits and not cross-reacting with other anterior pituitary hormones was administered IV to adult, male rats which received haloperidol 2.5 mg/kg or tartaric acid vehicle SC 22 hr and 12 hr before measurement of dopamine turnover. Comparable groups of haloperidol or vehicle-treated animals received normal rabbit serum as control. Dopamine synthesis or turnover rate was estimated by measurement of accumulation of L-dihydroxyphenylalanine following inhibition of L-aromatic amino acid decarboxylase with m-hydroxybenzylhydrazine. Haloperidol increased median eminence dopamine synthesis rate, and PRL antiserum completely prevented this effect, supporting the thesis that the haloperidol-induced increase in tuberoinfundibular dopamine turnover is mediated by PRL. PRL antiserum did not alter basal median eminence dopamine synthesis rate in male rats. In addition to its effect in median eminence, PRL antiserum blunted the haloperidol-induced increase in striatal dopamine synthesis rate, suggesting that the haloperidol-induced increase in nigroneostriatal dopamine turnover is mediated in part by PRL. Neither haloperidol nor PRL antiserum altered serotonin synthesis rate in mediobasal hypothalamus or striatum. The data provide further support for a mechanism by which PRL can regulate its own secretion. They also suggest that prolactin alters the activity not only of tuberoinfundibular but also of nigroneostriatal neurons.

Animals↗

PubMed1992

Immunocytochemical survey of haloperidol-induced immunoreactive changes of [Met]enkephalin-Arg6-Gly7-Leu8 in the rat forebrain.

It has already been demonstrated that chronic treatment with the dopamine receptor blocker, haloperidol, results in an increase of proenkephalin-A-derived peptides in the caudate-putamen (CP). To examine this phenomenon at the cellular level, we used immunocytochemistry to investigate the effects of haloperidol on [Met]enkephalin-Arg6-Gly7-Leu8 (MEAGL) immunoreactivity in the rat forebrain. After daily haloperidol (5 mg/kg, IP, for 6 days) or haloperidol decanoate (70 mg/kg, IM, given once or twice) treatment, immunoreactive neurons appeared diffusely in the whole CP and in the core part of the nucleus accumbens (Acb) and less frequently in the outer shell part of the Acb and the cell-dense layer of the tuberculum olfactorium (TuO). Increase of MEAGL-immunoreactive fibers in the CP, Acb, and TuO was also detected after these treatments, a particularly prominent increase being found in the striopallidal terminals in the globus pallidus and ventral pallidum. Haloperidol or haloperidol decanoate had no effect on MEAGL immunoreactivity in the cerebral cortex, amygdala, or hypothalamus. Reserpine treatment (5 mg/kg, IP, for 6 days) caused similar effects on the dorsal and ventral striopallidal system, and the direct injection of 6-hydroxydopamine (10 micrograms/5 microliters) into the CP led to the appearance of MEAGL-immunoreactive neurons in accordance with the depleted dopaminergic terminal area. These findings suggest that haloperidol influences enkephalinergic neurons region specifically and that in the dorsal and ventral striopallidal enkephalinergic system haloperidol increases MEAGL immunoreactivity in cell bodies, fibers, and terminals by blocking intrastriatal dopaminergic neurotransmission.

Animals↗

PubMed1996

Chronic treatment with eltoprazine does not lead to tolerance in its anti-aggressive action, in contrast to haloperidol.

The behavioral effects of eltoprazine and haloperidol during a 4 week treatment period were studied in the resident-intruder model of aggression in male rats. Eltoprazine, a serotonergic (5-HT1A/1B) agonist with specific anti-aggressive actions in animals, was compared to haloperidol, a neuroleptic often used to control behavioral disorders. Eltoprazine (1 or 3 mg/kg p.o.) and haloperidol (2 mg/kg p.o.) were given 60 min before a 10 min aggression test. Acutely, eltoprazine reduced aggression, without adversely affecting other behaviors. Eltoprazine (1 or 3 mg/kg p.o.) was subsequently given daily for 4 weeks and aggression tests were performed each week. The anti-aggressive effects of eltoprazine remained stable over the period of 4 weeks whereas exploration was increased. After a wash-out period of 1 week aggression had returned to baseline levels. Acutely given, haloperidol (2 mg/kg p.o.) completely reduced aggression concomitant with massive sedation. Significant tolerance developed to the sedatory actions of haloperidol over the 4 week treatment period. Aggression returned slowly, but remained below baseline values. One week after wash-out a new challenge with haloperidol (2 mg/kg p.o.) revealed significant tolerance. After 2 weeks wash-out aggression had returned to baseline. The data demonstrate persistent and specific anti-aggressive effects after eltoprazine showing no tolerance. In contrast, haloperidol showed tolerance and rebound effects for aggression. The development of tolerance after haloperidol has a different course for sedation than for the anti-aggressive action.

Aggression↗

PubMed2005

A post hoc analysis of transitioning to oral treatment with olanzapine or haloperidol after 24-hour intramuscular treatment in acutely agitated adult patients with schizophrenia.

BACKGROUND: Acutely agitated patients with schizophrenia might require treatment with IM antipsychotics, followed by a transition to oral medication. OBJECTIVE: The aim of this study was to assess the relationship between 24-hour IM and transitional oral dosages of 2 antipsychotic medications, olanzapine and haloperidol. METHODS: This post hoc analysis used data from a multinational, double-blind, randomized, placebo-controlled study comparing the efficacy of olanzapine, haloperidol, and placebo in acutely agitated inpatients aged > or =18 years with schizophrenia conducted at hospitals in 13 countries. Patients received 1 to 3 IM injections of olanzapine 10 mg or haloperidol 7.5 mg over 24 hours (IM phase), followed by 4 days of oral treatment with 5 to 20 mg/d of either antipsychotic (oral phase). Study patients were grouped according to which drug they received, and subgrouped based on whether they received a single or multiple IM injections. Rates of transition to lower (5-10 mg/d) versus higher (15-20 mg/d) dosages were compared within and between treatments. RESULTS: Data from 236 patients were analyzed (olanzapine, 121 patients [76 men, 45 women; mean (SD) age, 38.4 (12.2) years; mean (SD) weight, 74.9 (18.5) kg]; haloperidol, 115 patients [80 men, 35 women; mean (SD) age, 38.0 (10.2) years; mean (SD) weight, 75.4 (18.7) kg]). At the end of the IM phase, the rate of haloperidol patients who were transitioned to lower oral doses was significantly higher in the single-injection subgroup compared with the multiple-injection subgroup (P = 0.03); this difference was not found in the group receiving olanzapine. At day 4 of oral treatment, the rates of patients in the olanzapine and haloperidol groups who were transitioned to higher oral doses were significantly higher in the single-injection subgroups compared with the multiple-injection subgroups (P = 0.002 and =0.003, respectively). CONCLUSION: In this study, the proportion of agitated patients with schizophrenia who transitioned to higher dosages (15-20 mg) of olanzapine or haloperidol by day 4 of the oral switch was significantly greater in patients who were previously treated with a single IM injection of olanzapine (10 mg) or haloperidol (7.5 mg).right.

Administration, Oral↗

PubMed2005

Assay of the anti-psychotic drug haloperidol in bulk form, pharmaceutical formulation and biological fluids using square-wave adsorptive stripping voltammetry at a mercury electrode.

The cyclic voltammetric behavior of haloperidol at a hanging mercury drop electrode was studied in Britton-Robinson buffer series of pH 2.5-11 containing 40% (v/v) ethanol. A single two-electron irreversible cathodic peak was obtained which attributed to reduction of the CO double bond. In addition, a small enhanced adsorptive pre-wave was observed at less negative potentials over the pH range 3.5-11. Controlled adsorptive accumulation of haloperidol onto the hanging mercury drop electrode provided the basis for its direct trace assay in bulk form, pharmaceutical formulation and human biological fluids using square-wave adsorptive cathodic stripping voltammetry. Following preconcentration of bulk haloperidol onto the HMDE a well-developed square-wave cathodic peak was generated in Britton-Robinson buffer especially at pH values 9-10; its peak current showed a linear dependence on the concentration of haloperidol over the range 1 x 10(-9)M to 1.5 x 10(-6)M depending on the preconcentration duration. The procedural parameters for assay of haloperidol were studied. The achieved limits of detection (LOD) and quantitation (LOQ) were 3.83 x 10(-10)M and 1.28 x 10(-9)M bulk haloperidol, respectively. The procedure was successfully applied to assay haloperidol in tablets (Safinace) and in spiked human serum and urine. LOD of 3.3 x 10(-9)M and 5.46 x 10(-9)M, and LOQ of 1.10 x 10(-8) and 1.82 x 10(-8)M haloperidol were achieved in spiked human serum and urine samples, respectively.

Electrochemistry↗

PubMed2005

Ebselen attenuates haloperidol-induced orofacial dyskinesia and oxidative stress in rat brain.

Haloperidol-induced orofacial dyskinesia is an animal model of tardive dyskinesia whose pathophysiology has been related to basal ganglia oxidative stress. In this study the authors examined whether ebselen, an antioxidant organochalcogen with glutatione peroxidase-like activity, changes the behavioral and neurochemical effect of sub-chronic haloperidol administration. Haloperidol administered (12 mg/kg/week, sc) for 4 weeks caused a significant increase in vacuous chewing movements (VCMs), tongue protrusion (TP) and the duration of facial twitching (FT) observed in 4 weekly evaluations (p<0.05). Ebselen (30 mg/kg, ip), administered every other day, along with haloperidol (12 mg/kg/week, sc) once weekly, reversed the increase of VCMs and FT in four weekly evaluations (p<0.05), while TP frequency was reverted in the 2nd, 3rd, and 4th week. After the treatments and behavioral observation, biochemical parameters in segments of the brain were analyzed. Haloperidol significantly increased the thiobarbituric acid-reactive species (TBARS) levels in the cortex, striatum and subcortical parts of the brain. The co-administration of ebselen reversed the effect of haloperidol on TBARS production in cortex and striatum. The results of the present study clearly indicate that ebselen has a protective role against haloperidol-induced orofacial dyskinesia and reverses the increase in TBARS production caused by haloperidol administration. Consequently, the use of ebselen as a therapeutic agent for the treatment of tardive dyskinesia should be considered.

Animals↗

PubMed2006

Olanzapine and haloperidol in first episode psychosis: two-year data.

Few studies have assessed the comparative efficacy and safety of atypical and typical antipsychotic medications in patients within their first episode of psychosis. This study examined the effectiveness of the atypical antipsychotic olanzapine and the typical antipsychotic haloperidol in patients experiencing their first episode of a schizophrenia-related psychotic disorder over a 2-year treatment period. Two hundred and sixty-three patients were randomized to olanzapine or haloperidol in a doubleblind, multisite, international 2-year study. Clinical symptoms and side effects were assessed at baseline and longitudinally following randomization for the duration of the study. Olanzapine and haloperidol treatment were both associated with substantial and comparable reductions in symptom severity (the primary outcome measure) over the course of the study. However, the treatment groups differed on two secondary efficacy measures. Patients were less likely to discontinue treatment with olanzapine than with haloperidol: mean time (in days) in the study was significantly greater for those treated with olanzapine compared to haloperidol (322.09 vs. 230.38, p<0.0085). Moreover, remission rates were greater in patients treated with olanzapine as compared to those treated with haloperidol (57.25% vs. 43.94%, p<0.036). While extrapyramidal side effects were greater in those treated with haloperidol, weight gain, cholesterol level and liver function values were greater in patients treated with olanzapine. The data from this study suggest some clinical benefits for olanzapine as compared to haloperidol in first episode patients, which must be weighed against those adverse effects that are more likely with olanzapine.

Adult↗

PubMed2003

Possible mechanism of action in melatonin attenuation of haloperidol-induced orofacial dyskinesia.

Tardive dyskinesia (TD) is a late complication of prolonged neuroleptic treatment characterized by involuntary movements of the oral region. In spite of high incidence and much research, the pathophysiology of this devastating movement disorder remains elusive. Chronic treatment with neuroleptics leads to the development of abnormal oral movements in rats, referred to as vacuous chewing movements (VCMs). VCMs in rats are widely accepted as an animal model of TD. Rats chronically treated with haloperidol (1.5 mg/kg ip) significantly developed VCMs and tongue protrusions. Melatonin dose-dependently (1, 2, and 5 mg/kg) reversed the haloperidol-induced VCM and tongue protrusions frequencies. Biochemical analysis reveals that chronic haloperidol treatment significantly induced lipid peroxidation and decreased the forebrain glutathione (GSH) levels in the rats. Chronic haloperidol-treated rats also showed decreased levels of antioxidant defense enzymes, superoxide dismutase (SOD), and catalase. Coadministration of melatonin (1, 2, and 5 mg/kg) along with haloperidol significantly reduced the lipid peroxidation and restored the decreased GSH levels by chronic haloperidol treatment, and significantly reversed the haloperidol-induced decrease in forebrain SOD and catalase levels in rats. However, a lower dose of melatonin (1 mg/kg) failed to reverse chronic haloperidol-induced decreases in forebrain GSH, SOD, and catalase levels. In conclusion, melatonin could be screened as a potential drug candidate for the prevention or treatment of neuroleptic-induced orofacial dyskinesia.

Animals↗

PubMedDate not supplied

Economic evaluation of zuclopenthixol acetate compared with injectable haloperidol in schizophrenic patients with acute psychosis.

Zuclopenthixol acetate is a rapid-acting, injectable neuroleptic drug with a duration of action that allows for administration once every 2 to 3 days, in contrast to injectable haloperidol, which may require administration more than once daily. To assess the place of zuclopenthixol acetate in the treatment of acute episodes of schizophrenia, a cost-consequence analysis was performed comparing this new medication with short-acting, injectable haloperidol. The perspective of the Quebec health care system was adopted. The study population comprised patients diagnosed with schizophrenia who experienced an acute episode of psychosis and who were treated with intramuscular (i.m.) haloperidol. The study assessed patients for 9 days after the start of treatment. The literature was the principal source of comparative data about the clinical outcomes of the two treatments. The total cost associated with zuclopenthixol acetate i.m. or haloperidol i.m. was modeled using a decision tree built around the number of i.m. injections required to achieve stabilization. To establish costs, expert panels were consulted and patients' files were reviewed for a sample of schizophrenic patients who had been hospitalized in a large psychiatric or general hospital subsequent to a visit to the emergency department and had received a short-acting i.m. neuroleptic drug. Only a direct medical records costs were considered. Because zuclopenthixol acetate was not on the market at the time of the study, the file review did not allow for a direct estimate of its related costs but did provide an account of haloperidol use. The literature shows that zuclopenthixol acetate is similar to haloperidol with respect to the control of psychotic episodes; however, zuclopenthixol acetate is associated with increased sedation and a lower incidence of extrapyramidal symptoms. Using the base-case estimate for the number of injections required for stabilization, the incremental cost of zuclopenthixol acetate 50 mg over haloperidol was $25.00 (1995 Canadian dollars) per patient at the psychiatric hospital and $21.00 per patient at the general hospital. The results were sensitive to the estimate of the number of injections and the number of minutes of nursing care required by agitated patients. Zuclopenthixol acetate resulted in cost savings over haloperidol if it permits a reduction of 25% in minutes of nursing care or if 85% of patients require 2 injections or less (45% requiring 1 injection and 40% requiring 2). However, whichever drug is used, the cost of the injectable neuroleptic represents a small fraction of the cost of care for acutely psychotic patients.

Antipsychotic Agents↗

PubMed1989

Seemingly paradoxical jumping in cataleptic haloperidol-treated rats is triggered by postural instability.

Paradoxically, animals exhibiting haloperidol-induced cataleptic immobility can be induced to leap vigorously, by pushing them forward from behind. It is shown here that such jumping can also be produced by placing them on a board and tilting it tail-end upward until about 50 degrees above horizontal. In both situations, jumps only occurred when the animal's hindlegs began to slip forward, as they lost their postural stability. As alternatives to jumping from the slope, rats turned to face upwards (negative geotaxis), or adopted a spread-eagled posture during head-first downward sliding, with the body and head flattened against the substrate. All 3 responses to the sloping board were present in some undrugged rats. Such rats, and those given low doses of haloperidol (0.5, 1.0 mg/kg), were more likely to turn upwards than to jump or slide. At high doses (7.5, 10.0 mg/kg), they were more likely to slide downward than to turn or jump. Jumping was most likely to occur at an intermediate dose (5 mg/kg), approximately 60 min after injection. We suggest that in the absence of haloperidol, and at low doses, locomotion is dominant over reflexes defending static equilibrium, and hence rats are more likely to turn upwards (which involves stepping). In contrast, at higher doses, locomotion is more fully suppressed, reducing the likelihood of turning. At very high doses of haloperidol and later in the action of the drug, muscle tonus appears to be weakened, reducing the likelihood of jumping. This possibility was supported by the finding that combined injection of the optimal dose of haloperidol and 2 mg/kg diazepam reduced the ability to cling vertically (suggesting weakness of muscle tone). In such rats, jumping from the sloping board was decreased, and active downward sliding was increased. Thus, different factors influence the occurrence of jumping at different doses of haloperidol. However, these are all active defensive responses to postural instability, and hence are similar to the other reflexes used by haloperidol-treated rats to defend against displacement from static stable equilibrium, such as standing immobile, bracing, clinging, and righting. Jumping in response to loss of stability on the sloping board also occasionally occurred in undrugged rats. Unlike jumps by haloperidol-treated rats, those by undrugged animals only occurred when they could be directed to a safe landing place. Thus, if the board faced the edge of the table, so that the jump would carry the animal into space over the edge, undrugged rats either did not jump or jumped off the side of the board onto the table.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1998

Correlation between steady-state plasma concentrations (Css) of bromperidol and haloperidol.

1. Bromperidol is a close structural analogue of haloperidol, and its metabolic pathways are similar to those of haloperidol. The authors studied the correlation between the Css of bromperidol and haloperidol. 2. The subjects were 16 schizophrenic inpatients. Fourteen patients received firstly bromperidol 12 mg/day and secondly haloperidol 12 mg/day, while the remaining two patients received the two treatments in the opposite sequence. 3. Blood samplings were performed 2-3 weeks after the initiation of each treatment, and the Css of bromperidol, haloperidol and their reduced metabolites were measured by high-performance liquid chromatography. 4. Neither the correlation between the Css of bromperidol and haloperidol (r = 0.246) nor that between the Css of reduced bromperidol and reduced haloperidol (r = 0.142) was significant. 5. The present study thus suggests that the Css of bromperidol and haloperidol do not correlate well in individuals.

Adult↗

PubMed2000

Risperidone versus haloperidol in psychotic patients with disturbing neuroleptic-induced extrapyramidal symptoms: a double-blind, multi-center trial.

BACKGROUND: A randomized, double-blind, multi-center trial was started to compare the severity of extrapyramidal symptoms (EPS) during risperidone and haloperidol treatment in schizophrenic patients who had disturbing EPS during their previous neuroleptic treatment. Additional objectives of this trial were comparing the antipsychotic effectiveness of the two treatments and the use of antiparkinsonian medication. METHODS: Effects of flexible doses of risperidone and haloperidol were compared in 77 psychotic patients (83% with chronic schizophrenia) with disturbing neuroleptic-induced EPS (risperidone 40 patients, haloperidol 37). The trial was completed by 47 patients: 25 in the risperidone group (12 women, 13 men), and 22 in the haloperidol group (10 women, 12 men). RESULTS: An adequate antipsychotic effect was obtained in most patients by both treatments. The primary aim of this trial was comparing parkinsonism measured with the extrapyramidal syndrome rating scale (ESRS) during treatment with risperidone and haloperidol. Two primary parameters were selected: the change from baseline to the worst score during treatment of ESRS II (parkinsonism) and ESRS VI (clinical global impression of severity of parkinsonism). The CGI of severity of parkinsonism was better with risperidone (P=0.025), while the parkinsonism total score tended to be better with risperidone (P<0. 10). Before the double-blind treatment, 34 (of the 77) had used antiparkinson medication (risperidone 18, haloperidol 16). During the double-blind treatment phase, 21 patients had used antiparkinson medication (risperidone 11, haloperidol 10). The larger reduction of parkinsonism in the risperidone group was not due to a difference in the use of anti-parkinsonian medication. CONCLUSIONS: In this group of schizophrenic patients with disturbing EPS during previous neuroleptic treatment, a stronger reduction of parkinsonism was observed with risperidone than with haloperidol.

Antipsychotic Agents↗

PubMed1997

The acute and long-term effect of olanzapine compared with placebo and haloperidol on serum prolactin concentrations.

Prolactin elevation is both a common and a persistent event with the currently marketed antipsychotics, excluding clozapine. Elevations have been associated with both acute (galactorrhea, amenorrhea) and chronic (predisposition to osteoporosis) treatment-emergent adverse events. One of the defining criteria for an atypical antipsychotic is the relative lack of persistent prolactinemia. A double-blind, placebo- (N = 68) and haloperidol- (Hal: 15 +/- 5 mg/day, N = 69) controlled trial of three dose ranges of olanzapine (Olz-L: 5 +/- 2.5 mg/day, N = 65; Olz-M: 10 +/- 2.5 mg/day, N = 64; Olz-H: 15 +/- 2.5 mg/day, N = 69) in the treatment of schizophrenia afforded the opportunity to assess the temporal course of the influence of olanzapine and haloperidol on serum prolactin concentration. Consistent with its potent D2 antagonism, haloperidol was associated with a statistically significantly higher incidence of treatment-emergent prolactin elevation (72%) than seen with placebo (8%; p < 0.001) at week 2 of therapy. Expectedly, this elevation was also persistent at weeks 4 and 6. In contrast, olanzapine-associated treatment-emergent prolactin elevations were both lower in magnitude and transient. At week 2, 38% of the Olz-H, 24% of the Olz-M, and 13% of the Olz-L treatment groups exhibited a treatment-emergent prolactin elevation, with a mean increase of 0.35, 0.52, and 0.61 nmol/l, respectively; for haloperidol the mean increase was 1.23 nmol/l. For only the Olz-M and the Olz-H treatment groups did the week 2 incidence of treatment-emergent prolactin elevations differ statistically significantly from placebo. Both the incidence of elevations and the mean increase, in prolactin concentration were less than that seen with haloperidol. Furthermore, by treatment week 6, all three olanzapine groups exhibited incidences of treatment-emergent prolactin elevation that were comparable to placebo and were statistically significantly less than observed with haloperidol. Rapid adaptation was observed in the temporal course of prolactin elevations associated with olanzapine based on both the categorical analysis of treatment-emergent high values and the analyses of temporal change in mean concentrations. In contrast to haloperidol, the magnitudes of the treatment-emergent elevations associated with olanzapine were minimal. The rates of elevation were approximately one-half to one-third those observed with haloperidol and were significantly more transient. Olanzapine, even at the highest doses (15 +/- 2.5 mg/day) used, was not associated with persistent elevations of prolactin, consistent with an 'atypical' pharmacologic profile.

Adult↗

PubMed2002

Biochemical effects in brain of low doses of haloperidol are qualitatively similar to those of high doses.

Typical and atypical antipsychotic drugs (APD) show differential effects in brain on both dopamine output and activation of Fos-like immunoreactivity (FLI) in dopamine nerve terminal regions. Typical APD increase dopamine output preferentially in the core and atypical APD increase dopamine output preferentially in the shell of the nucleus accumbens (NAC). Whereas both typical and atypical APD increase FLI in NAC, typicals cause FLI activation in the striatum and atypicals cause FLI activation in the prefrontal cortex. Clinically, low doses of haloperidol cause less side-effects than higher doses, and low-dose haloperidol has been suggested as a cost-effective alternative to atypical APD. Here, in vivo voltammetry in anaesthetised, pargyline-pretreated rats was used to measure dopamine output in the two subdivisions of the NAC and, in addition, immunohistochemistry was used to assess FLI activation in dopamine target areas, following acute haloperidol administration. Haloperidol, 0.001 and 0.01 mg/kg i.v., caused a significantly higher dopamine output in the core than in the shell of the NAC. Moreover, haloperidol 0.05 and 0.5, but not 0.005, mg/kg s.c. increased FLI in the NAC and the striatum, but not in the medial prefrontal cortex. Thus, even extremely low doses of haloperidol generate, in principle, the same biochemical effects in brain as higher doses, and these effects remain different from those of atypical APD. These biological data indicate that clinical differences between haloperidol and atypicals are qualitative rather than dose-dependent. Consequently, our results do not support the use of low-dose haloperidol as replacement for atypical APD in the treatment of schizophrenia.

Amygdala↗

PubMed2003

The influence of dyslipidemia on the plasma protein and lipoprotein distribution of haloperidol.

The objective of this study is to determine the effect of dyslipidemia on the plasma protein and lipoprotein distribution of haloperidol. In doing so, total plasma cholesterol and triglyceride levels were adjusted by adding differing volumes of concentrated low-density lipoproteins and very-low-density lipoproteins to normolipidemic plasma. Following the incubation of [3H]-haloperidol plus cold haloperidol (18 microg/ml) the plasma was separated into its lipoprotein and lipoprotein deficient fractions by density gradient ultra centrifugation and [3H]-haloperidol distribution was determined. Our results revealed a significant positive correlation between total cholesterol concentration and haloperidol recovery in the low-density lipoprotein fraction (r=0.975, df=13, P<0.005). A positive correlation was also observed between total plasma triglyceride concentration and haloperidol recovery from both the very low-density lipoprotein (r=0.965, df=16, P<0.002) and low-density lipoprotein fractions (r=0.935, df=16, P<0.005). This redistribution was the result of haloperidol leaving the lipoprotein-deficient fraction were it is primarily bound to albumin and alpha(1)-acid glycoprotein. This redistribution of haloperidol may influence its clinical efficacy.

Binding, Competitive↗

PubMed2004

Clozapine but not haloperidol Re-establishes normal task-activated rCBF patterns in schizophrenia within the anterior cingulate cortex.

Our previous work has identified that unmedicated volunteers with schizophrenia have regional cerebral blood flow (rCBF) activation patterns inappropriately related to the cognitive demand of a task in anterior cingulate cortex (ACC). Using positron emission tomography (PET) with (15)O water, we compared task-induced rCBF patterns induced by haloperidol or clozapine in individuals with schizophrenia. We hypothesized that clozapine, given its superior clinical action, would tend to normalize the abnormal task-activated response in ACC more than haloperidol. Schizophrenia volunteers (SVs) (n=6) and normal volunteers (NVs) (n=12) were trained to perform a tone discrimination task with 70-80% accuracy. They were then scanned during three task conditions: (1). Rest, (2). sensory motor control (SMC) task, and (3). decision task (DEC). SVs were initially scanned after withdrawal of all psychotropic medication and again after treatment with therapeutic doses of haloperidol (n=5) and/or clozapine (n=5). rCBF values, sampled in the grown maxima of the task-activated ACC cluster, were analyzed between groups and task conditions. Task performance was similar across the unmedicated, haloperidol- and clozapine-medicated SV groups. There was a reduction in accuracy in the haloperidol SV group compared to the NVs. Group and task conditions affected rCBF in the ACC. Clozapine, but not haloperidol, reversed the abnormal ACC rCBF pattern in unmedicated SV to normal. The clozapine-treated SV group showed a rCBF pattern similar to the NV group in that ACC activation was not observed during the control task but occurred during the decision condition. The pattern seen in the haloperidol-treated SV group was similar to the unmedicated SV group in that ACC activation was seen during the control task and no further activation was seen during the DEC. We report that clozapine, but not haloperidol, normalizes anterior cingulate rCBF patterns in schizophrenia during a cognitive task. Based on these preliminary data, we propose that this pattern may account for the superior therapeutic effect of clozapine and represents a surrogate marker of this action.

Acoustic Stimulation↗

PubMed2006

Blockade of 5-HT2a receptors reduces haloperidol-induced attenuation of reward.

Previous studies have shown that effective antipsychotic medications attenuate reward, an effect that is generally attributed to their effectiveness at blocking the dopamine D2-like receptors. As blockade of the serotonin type 2a (5-HT2a) receptors is a common property of the newer antipsychotics, the present study compared the effect of haloperidol, clozapine, and M100907 (a selective 5-HT2a antagonist) and the combined effect of haloperidol and M100907 treatment on brain stimulation reward (BSR). Experiments were performed on male Sprague-Dawley rats trained to produce an operant response to obtain electrical stimulation in the lateral hypothalamus. Measures of reward threshold were determined in different groups of rats using the curve-shift method using fixed current intensity and variable frequency before and at different times after injection of haloperidol (0.01, 0.05, 0.1, and 0.25 mg/kg), clozapine (1, 7.5, 15, and 30 mg/kg), M100907 (0.033, 0.1, and 0.3 mg/kg), or their vehicle. The effect of M100907 (0.3 mg/kg) on the attenuation of BSR by a sub- and suprathreshold dose of haloperidol was studied in another group of rats. Clozapine produced a dose-orderly increase in reward threshold with a mean maximal increase of 50%; at high doses, clozapine induced cessation of responding in several animals at different time periods. Haloperidol induced a dose-dependent increase in reward threshold, with the mean maximal increase (75%) being observed at the highest dose; it also produced a dose-dependent reduction of maximum rates of responding. M100907 failed to alter reward at any of the doses tested and had no effect on the subthreshold dose (0.01 mg/kg) of haloperidol. But when combined with a suprathreshold dose of haloperidol, M100907 reduced the reward-attenuating effect of haloperidol. These results show that 5-HT2a receptors are unlikely to constitute a component of the reward-relevant pathway activated by lateral hypothalamic stimulation. However, blockade of 5-HT2a receptors may account for the relatively lower level of reward attenuation produced by clozapine, and predict that antipsychotic medications that have a high affinity for the 5-HT2a receptor may be less likely to induce dysphoria.

Analysis of Variance↗

PubMed1998

Modulation of the N-methyl-D-aspartate receptor by haloperidol: NR2B-specific interactions.

The dopaminergic antagonist haloperidol has an eight- to 10-fold higher affinity for NMDA receptors containing the NR2B (epsilon2) subunit, showing the same subunit specificity as ifenprodil, polyamines, and magnesium. In the present study, we have compared the effects of mutations altering polyamine and ifenprodil sensitivity on haloperidol sensitivity of NMDA receptors. As seen for spermidine stimulation, high-affinity haloperidol inhibition is governed by the region around amino acid 198, based on results from chimeric murine NR2A/NR2B (epislon1/epsilon2) receptors. Mutation of epsilon2E201 in this region to asparagine or arginine causes a 10-fold decrease in the ability of haloperidol to inhibit 125I-MK-801 binding. Epsilon2E201 does not govern the interactions of ifenprodil, because all of the mutants at epsilon2E201 exhibited wild-type affinity for ifenprodil. Mutation of epsilon2R337 causes a 400-fold loss in apparent affinity for ifenprodil but does not change the effects of haloperidol. The structural determinants of spermidine stimulation do not perfectly match those for haloperidol inhibition, as mutations of E200 remove haloperidol inhibition but do not alter polyamine stimulation. The present results thus demonstrate that although spermidine, haloperidol, and ifenprodil share subunit selectivity and overlapping pharmacology, they also have specific structural determinants.

Amino Acid Sequence↗