Therapeutic effect and safety of increasing doses of risperidone (R 64766) in psychotic patients

Current and potential pharmacological and psychosocial interventions for anxiety symptoms and disorders in patients with schizophrenia: structured review

OBJECTIVE

Between 30% and 62% of patients with schizophrenia present with co-morbid anxiety disorders that are associated with increased overall burden. Our aim was to summarize current and potential interventions for anxiety in schizophrenia.

DESIGN

Structured review, summarizing pharmacological and psychosocial interventions used to reduce anxiety in schizophrenia and psychosis.

RESULTS

Antipsychotics have been shown to reduce anxiety, increase anxiety, or have no effect. These may be augmented with another antipsychotic, anxiolytic, or antidepressant. Novel agents, such as L-theanine, pregabalin, and cycloserine, show promise in attenuating anxiety in schizophrenia. Psychosocial therapies have been developed to reduce the distress of schizophrenia. Cognitive behavioural therapy (CBT) has shown that benefit and refinements in the therapy have been successful, for example, for managing worry in schizophrenia. CBT usually involves more than 16 sessions, as short courses of CBT do not attenuate the presentation of anxiety in schizophrenia. To address time and cost, the development of manualized CBT to address anxiety in schizophrenia is being developed.

CONCLUSIONS

The presence of coexisting anxiety symptoms and co-morbid anxiety disorders should be ascertained when assessing patients with schizophrenia or other psychoses as a range of pharmacological and psychosocial treatments are available.

Use of Atypical Antipsychotics on an As-Needed Basis

Objective:

To review the literature and determine whether atypical antipsychotics should be used on an as-needed (prn) basis.

Data Sources:

Pertinent English-language literature dealing with atypical antipsychotics, typical antipsychotics, phamacokinetics, and prn dosing strategies was retrieved from a MEDLINE search (1960–1995).

Data Extraction:

Articles that discussed either pharmacokinetic parameters or the rationale for using antipsychotics on a prn basis.

Data Synthesis:

Administration of typical antipsychotics on a prn basis, either alone or in combination with scheduled antipsychotics, is a common practice. However, it has recently been recognized that the atypical agents, clozapine and risperidone, are also being prescribed for prn dosing. Clozapine has a sedative component that may provide a therapeutic benefit when prescribed prn, but it is also associated with dose-related seizures and orthostatic hypotension. Risperidone does not appear to exhibit sedation, except at very high doses.

Conclusions:

The risk-to-benefit ratio is not acceptable in using the atypical antipsychotic agents on a prn basis. There are documented safety and efficacy data that support the use of the typical antipsychotic agents such as chlorpromazine, or haloperidol in combination with lorazepam, on a prn basis. These latter choices are also more cost-effective.

The Pharmacotherapy of Human Aggression: A Review

Aggression is a common treatment problem that may be associated with several disorders including schizophrenia, schizoaffective disorder, acute mania/bipolar disorder, personality disorders, substance abuse disorders, medical disorders, neurological disorders, and medication misadventures. Aggression is not a linear entity, it is a multidimensional problem influenced by a patient's environment and biological, psychological, and/or neurological status. It follows that if one has a multidimensional treatment problem, then a compre hensive treatment plan must be used to achieve optimal management. The comprehensive treatment of aggression should include a thorough baseline evaluation, regular objective measurement of aggression severity using a rating scale (eg, Overt Aggression Scale), psychological interventions, behavioral interventions, pharmacotherapy and, if necessary, seclusion and/or restraint. The pharmacotherapy of aggres sion includes the traditional antipsychotics and benzodiazepines, which are most commonly used; other pharmacotherapies frequently selected include the β-blockers, carbamazepine, and lithium. Despite these pharmacotherapeutic options and despite a pharmacological rationale for each one, the medications used for the treatment of aggression are at least in part nonspecific for aggression. The nonspecificity of these pharmacotherapies is best exemplified by the common use of multiple drug regimens. This may then lead to drug misadventures either in the form of drug-drug interactions, adverse effects, or toxicity. The serenics are a class of phenylpiperazine compounds that have exhibited some promise as being more selective anti- aggression drugs. Eltoprazine, the first member of this new class, is in early phases of human investigation. Copyright © 1996 by W.B. Saunders Company

Clinical pharmacology of dopamine-modulating agents in Tourette's syndrome

Forty years of research and clinical practice have proved dopamine (DA) receptor antagonists to be effective agents in the treatment of Tourette's syndrome (TS), allowing a significant tic reduction of about 70%. Their main effect seems to be mediated by the blockade of the striatal DA-D2 receptors. Various typical and atypical agents are available and there is still discord between experts about which of them should be considered as first choice. In addition, there are suggestions to use DA receptor agonists such as pergolide or non-DA-modulating agents. The present chapter is focusing on the clinical pharmacology of DA-modulating agents in the treatment of TS. The introduction outlines their clinical relevance and touches on the hypotheses of the role of DA in the pathophysiology of TS. Subsequently, general information about the mechanisms of action and adverse effects are provided. The central part of the chapter forms a systematic review of all DA-modulating agents used in the treatment of TS, including an overview of studies on their effectiveness, and a critical discussion of their specific adverse effects. The present chapter closes with a summary of the body of evidence and a description of the resulting recommendations for the pharmacological treatment of TS.

A review of liver function tests during treatment with atypical antipsychotic drugs: a chart review study

OBJECTIVE

Atypical antipsychotic drugs commonly cause asymptomatic increase in the liver enzymes and serum bilirubin levels. However they rarely may induce a serious hepatic toxicity. In this article we aimed to evaluate the effect of atypical antipsychotic drugs namely olanzapine, risperidone and quetiapine on the hepatic enzymes and serum bilirubin levels in psychiatric patients.

METHOD

Chart reviews of 312 patient followed-up at Psychiatry Department of Zonguldak Karaelmas University Hospital were examined in detail. The patients whose baseline and follow-up liver function tests including alanine aminotransfeaminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transferase (GGT), alkaline phosphotase (ALP) and serum bilirubin that were measured before and within the treatment period of first and sixth months were enrolled. Forty eight males and 62 females whose ages ranging from 12 to 65 years were eligible for this study (no pregnant case was present).

RESULTS

The repartition according to treatment is as follows: olanzapine (n=33), risperidone (n=29), and quetiapine (n=48). Two of the 110 patients (1.8%) presented with increased AST levels of up to 4 fold and ALT of thrice the basal level and needed to stop treatment (AST increase in one female with olanzapine 20 mg/day; ALT increase in one male with olanzapine 30 mg/day). Thirty of the 110 patients (27.2%) showed asymptomatic increases in ALT, AST, GGT and serum bilirubin levels in the first month of the study. After 6 months of the treatment, abnormalities in the liver function tests were observed in 25 patients (22.7%).

CONCLUSION

These results were in accordance with previous studies that asymptomatic increase of liver enzymes are common but significant liver enzyme elevations are rare during atypical antipsychotic treatment. We suggest that obtaining baseline liver enzyme tests before atypical antipsychotic therapy and monitoring regularly specifically in patients with risk factors for liver damage during therapy.

Synergistic effect of galantamine with risperidone on impairment of social interaction in phencyclidine-treated mice as a schizophrenic animal model

Social withdrawal is the first sign and key component of the negative symptoms of schizophrenia. The efficacy of risperidone, an atypical antipsychotic, on the symptom is practically limited by dose-dependent side effects in clinical trials, therefore there is the need for adjuvant treatments. In the present study, we aimed to investigate the synergistic effect and mechanism of risperidone and galantamine, which is a nicotinic acetylcholine receptor (nAChR)-allosteric modulator and a modest cholinesterase inhibitor, on phencyclidine (PCP)-treated mouse model of social withdrawal. At non-effective doses by themselves, co-administration of galantamine (0.05mg/kg) and risperidone (0.05mg/kg) showed synergistic effects on PCP-induced impairments of social interaction and dopamine release in the medial prefrontal cortex (mPFC). The behavioral synergistic effect was abolished by the administration of a dopamine-D(1) receptor antagonist, SCH 23390 (0.02mg/kg, systemic; or 0.02microg/0.5microL/mouse, intra-mPFC), and a nAChR antagonist, mecamylamine (3mg/kg), but not a muscarinic receptor antagonist, scopolamine (0.1mg/kg). Mecamylamine (3mg/kg) also abolished the synergistic effect on dopamine release in the mPFC. We conclude that galantamine may have synergistic effect with risperidone on the negative symptom of social withdrawal in schizophrenia, which is mediated by dopamine-D(1) receptors in the mPFC through nAChR activation-increased dopamine release.

Effects of short- and long-term risperidone treatment on prolactin levels in children with autism

BACKGROUND

The effects of short- and long-term risperidone treatment on serum prolactin were assessed in children and adolescents with autism.

METHODS

Patients with autism (N = 101, 5-17 years of age) were randomized to an 8-week trial of risperidone or placebo and 63 then took part in a 4-month open-label follow-up phase. Serum samples were obtained at Baseline and Week-8 (N = 78), and at 6-month (N = 43) and 22-month (N = 30) follow-up. Serum prolactin was determined by immunoradiometric assay; dopamine type-2 receptor (DRD2) polymorphisms were genotyped.

RESULTS

Baseline prolactin levels were similar in the risperidone (N = 42) and placebo (N = 36) groups (9.3 +/- 7.5 and 9.3 +/- 7.6 ng/ml, respectively). After 8 weeks of risperidone, prolactin increased to 39.0 +/- 19.2 ng/ml, compared with 10.1 +/- 8.8 ng/ml for placebo (p < .0001). Prolactin levels were also significantly increased at 6 months (32.4 +/- 17.8 ng/ml; N = 43, p < .0001) and at 22 months (N = 30, 25.3 +/- 15.6 ng/ml, p < .0001). Prolactin levels were not associated with adverse effects and DRD2 alleles (Taq1A, -141C Ins/Del, C957T) did not significantly influence baseline levels or risperidone-induced increases in prolactin.

CONCLUSIONS

Risperidone treatment was associated with two- to four-fold mean increases in serum prolactin in children with autism. Although risperidone-induced increases tended to diminish with time, further research on the consequences of long-term prolactin elevations in children and adolescents is needed.

Alterations of serotonin transmission in schizophrenia

A role for serotonin alterations in the pathophysiology of schizophrenia has long been suspected because of the psychotogenic effects of serotonergic agonists and the therapeutic effects of 5-HT(2) antagonism. This chapter is a review of the evidence derived from pharmacological studies, postmortem, and imaging studies that have assessed the role of serotonin transmission in schizophrenia. While a clear picture of specific serotonergic alterations in schizophrenia has not emerged despite much research, this review reinforces a modulatory role of serotonergic agents on dopamine transmission in schizophrenia, which may contribute to the therapeutic effects of atypical antipsychotics.

Pharmacological treatment of primary negative symptoms in schizophrenia: a systematic review

BACKGROUND

Optimal treatment of primary negative symptoms is important because their presence is associated with poor outcome.

AIMS

To systematically review all studies dealing with the efficacy of pharmacological agents on primary negative symptoms.

METHOD

A comprehensive search of the relevant literature was undertaken using electronic database, reference lists and personal contact.

RESULTS

There is a lack of standardized research designs. Amisulpride is the most extensively studied drug with respect to efficacy against primary negative symptoms. At low doses it demonstrates a consistent, modest effect compared to placebo, though not to conventional antipsychotics and has yet to be tested against other atypicals. Evidence from multiple studies that used simple statistical analyses and inclusion criteria for patients with primary negative symptoms does not support a direct effect for clozapine. Path-analysis studies support the direct effects of risperidone, olanzapine, sertindole and aripiprazole, however, different statistical analyses of the same risperidone study produced conflicting results and the direct effects of olanzapine were not confirmed in selected patients with primary negative symptoms. There are no studies supporting the use of ziprasidone or quetiapine. The effects of typical antipsychotics on primary negative symptoms are inconclusive and likely to depend on drug dosages. Selective serotonin reuptake inhibitors (SSRIs), mirtazepine and NMDA agonists show early promise but require further study. Novel agents such as selegiline, naltrexone, dehydroepiandrosterone, galantamine, Ginkgo, nitric oxide, L-deprenyl and pergolide show positive effects on general negative symptoms but remain untested against primary negative symptoms.

CONCLUSIONS

Further studies using standardized selective inclusion criteria and controlling for chronicity are needed. Research guidelines are discussed.

Pharmacokinetic profile of long-acting injectable risperidone at steady-state: comparison with oral administration

The single dose pharmacokinetic profiles of long-acting injectable (LAI) risperidone and oral risperidone were extrapolated to steady-state. Plasma concentrations of the active moiety (unchanged risperidone + 9-hydroxy-risperidone) were measured by radioimmunoassay up to 72 h after a single oral 1 mg dose of risperidone in healthy volunteers (n = 12), and up to 84 days after a single intramuscular injection of 50 mg LAI risperidone in schizophrenic patients (n = 26). These data were projected to multiple dose regimens (4 mg/day for the oral formulation and 50 mg every 2 weeks for LAI formulation) using the software package WinNonlin, and average steady-state pharmacokinetic profiles were predicted. The most interesting results, obtained at steady-state, were a lower predicted peak plasma level (46 vs. 62 ng/ml) and a lower predicted degree of fluctuation between Cssmax and Cssmin (53 vs 145%) with LAI compared to oral administration, which is in line with actual steady state data on LAI risperidone. In conclusion, the pharmacokinetic profile of LAI risperidone administered every 2 weeks ensures a steady-state profile with concentrations falling in the interval observed with an equivalent oral dose but with lower and less fluctuations (i.e. 1/2 weeks vs 1/day).

Risperidone: a review

When the risk of agranulocytosis associated with clozapine, the prototype of the second-generation neuroleptics, became apparent, its prescription was restricted to patients refractory to classical neuroleptics such as chlorpromazine and haloperidol. This stimulated the development of several novel second-generation antipsychotics with a clinical profile similar to that of clozapine. These novel antipsychotics, which include risperidone, olanzapine and others, are characterised by different pharmacological structures, and also to a certain degree by different pharmacological mechanisms. Following the increased research on the novel second-generation antipsychotics, it became apparent that they not only have the advantage of better extrapyramidal tolerability than the classical neuroleptics, but also have a broader efficacy spectrum (i.e., advantages in the treatment of negative and depressive symptoms and cognitive disturbances in the context of schizophrenia). Risperidone was specifically designed by Paul Janssen as a combined 5-HT2A and D2 receptor antagonist, thus following the pharmacological mechanism thought to be responsible for the antipsychotic effects of clozapine. After its advent in the 1990s as the first novel second-generation antipsychotic, risperidone achieved worldwide acceptance. The following review gives an overview of the huge clinical database available for risperidone in the field of schizophrenia.

Multiple dose pharmacokinetics of risperidone and 9-hydroxyrisperidone in Chinese female patients with schizophrenia

AIM

To study the multiple dose clinical pharmacokinetics of risperidone and its main active metabolite, 9-hydroxyrisperidone, in Chinese female patients with schizophrenia.

METHODS

The subjects were 23 Chinese female inpatients aged 18-65 years who met the CCMD-III (third revision of the Chinese Criteria of Mental Disorders) criteria for schizophrenia. Subjects were tested after 17 d of treatment with 2 mg risperidone twice daily. Plasma concentrations of risperidone and 9-hydroxy-risperidone were assayed by using validated high performance liquid chromatography-mass spectrometry (HPLC-MS) methods.

RESULTS

Risperidone was rapidly absorbed (Tmax was 1.6 h) and its T1/2 in plasma was short (3.2 h). 9-hydroxy-risperidone was quickly metabolized from the parent drug with a mean Tmax of 2.5 h. It had a long half-life of 24.7 h. The C(ss)(av) of risperidone and 9-hydroxy-risperidone were 36.9+/-33.1 and 110.6+/-30.5 microg x h x L(-1), respectively, and the AUC(ss)0-12 were 443.2+/- 397.4 and 1327.2+/- 402.3 microg x h x L(-1), respectively. CL/F and V/F of risperidone were 8.7+/- 6.2 L/h and 34.1+/- 24.3 L, respectively. Interindividual variations for pharmacokinetic parameters were quite large for risperidone. All 23 subjects experienced high prolactin levels when treated with risperidone. However there was no correlation between prolactin level and the concentration of risperidone, 9-hydroxy-risperidone, or the active moiety.

CONCLUSION

Risperidone showed large interindividual variations in pharmacokinetics. Administration of risperidone resulted in high serum prolactin levels. The results indicate that systemic exposure to risperidone and 9-hydroxy-risperidone in female Chinese schizophrenic patients is higher relative to published data for white Caucasian patients. Larger studies regarding the PK/PD relationship may be required to develop a reasonable clinical dosage regimen for Chinese female patients.

Risperidone-induced prolactin elevation in a prospective study of children, adolescents, and adults with mental retardation and pervasive developmental disorders

OBJECTIVE

Risperidone is widely prescribed for aggression and self-injury in children, adolescents, and adults with mental retardation (MR) and pervasive developmental disorders (PDD). Risperidone elevates prolactin more than other atypical antipsychotic medications. Females may show greater prolactin elevation than males.

METHOD

In this relatively long-term study of risperidone efficacy and safety for aggression and self-injury in children, adolescents, and adults with MR and PDDs, serum prolactin was measured in a 21-subject subset during the course of a double-blind, placebo-controlled trial. Prolactin was measured in ng/mL at baseline, once during acute treatment, and once during maintenance.

RESULTS

In children and adolescents (n=10), mean age of 12.5 years, prolactin increased from mean 13.2+/-8.6 at baseline to 31.0+/-11.6 acutely and remained elevated at 37.9+/-10.4 in maintenance. In adults, mean age of 35.3 years, prolactin increased more markedly from 11.6+/-7.4 baseline (n=11) to 93.3+/-54.2 acutely but decreased to 67.8+/-62.9 in maintenance (n=7). Prolactin remained significantly elevated above normal in all subjects for at least 26 weeks. Mean prolactin of adult females, while similar to that of adult males at baseline, was 2.2 times male levels acutely and 3.7 times greater in maintenance.

CONCLUSION

In this small subset, mean prolactin elevation persisted for at least 26 weeks. In adults, females showed significantly greater elevations than males.

Naturalistic observation on the hepatic enzyme changes in patients treated with either risperidone or olanzapine alone

This retrospective study aimed to compare differences in hepatic enzyme elevation during treatment with either risperidone or olanzapine alone in patients with psychotic disorders. The charts were reviewed for six hundred and sixty-seven (667) inpatients with psychotic disorders who were treated with either risperidone (n=289) or olanzapine (n=145) alone at a university-affiliated hospital between 1998 and 2002. Frequencies of elevation greater than the reference level in any enzyme among aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphotase (ALP) were higher in the olanzapine-treated group (26.9%) than in the risperidone-treated group (14.2%) [odds ratio (OR)=2.225, 95% confidence interval (CI)=1.362-3.638, P=0.002]. Frequencies of elevation greater than the reference level in ALT were higher in the olanzapine-treated group than in the risperidone-treated group (OR=2.182, P=0.004), as were frequencies with two-fold (OR=3.064, P=0.017) and three-fold (OR=2.883, P=0.039) elevation. Recovery time was longer in the olanzapine-treated group than in the risperidone-treated group (P=0.0059), as was latency time (P=0.0044). These results suggest that there are potential differences in antipsychotic-associated hepatic enzyme alterations between risperidone and olanzapine treatment. Controlled, prospective studies should be conducted to identify the risk factors associated with an alteration in hepatic enzymes related to treatment with risperidone and olanzapine.

RESISTANCE TO EXCESSIVE BODYWEIGHT GAIN IN RISPERIDONE-INJECTED RATS

1. The present study was carried out to explain the resistance of rats injected subcutaneously with risperidone, the atypical antipsychotic drug, for 21 consecutive days at 0.1 mg/kg per day (a dose equivalent to the one used for patients) to result in an excessive bodyweight despite the increase in diet-uptake in rats against risperidone-induced decrease in body temperature. 2. Rectal temperature measurements were made in 8-week-old male Sprague-Dawley rats maintained under standard laboratory conditions using a 12 h daylight cycle. A s.c. injection of risperidone (0.05 mg/kg) produced hypothermia in rats, which was observed during the daily injection for 21 consecutive days. 3. Sera, white and brown adipose tissues, skeletal muscle and liver were extracted from 8-week-old male Sprague-Dawley rats injected subcutaneously with risperidone (0.01 or 0.1 mg/kg per day) or a vehicle for 21 consecutive days. Serum levels of lipids, ketones and thyroid hormone were measured. The mRNA expression levels in these tissues and organs of the genes encoding the substances involved in heat production and/or lipid metabolism were investigated by using quantitative real-time polymerase chain reaction amplification. 4. Serum nonesterified fatty acid levels in risperidone 0.1 mg/kg per day s.c. injected rats were significantly lower than those in vehicle-injected ones. Serum beta-hydroxybutyrate levels in risperidone-injected rats tended to decrease compared with those in vehicle-injected ones. The serum level of neither triiodothyronine nor thyroxine was affected by risperidone s.c. injection at the doses examined, although their values were within normal limits. 5. Risperidone injection (0.1 mg/kg per day) for 21 consecutive days upregulated mRNA expressions in white adipose tissue of uncoupling protein 3 which dissipates energy as heat; peroxisome proliferator-activated receptor (PPAR) gamma coactivator 1alpha which activates mitochondrial biogenesis to expand the oxidative machinery; and PPARalpha which is necessary for the fat-depletion of adipocytes for thermogenesis. The mRNA of lipogenic enzymes (acetyl-CoA carboxylase alpha, fatty-acid synthase and glycerol-3-phosphate acyltransferase), hormone sensitive lipase and beta1-adrenoceptor were also enhanced in white adipose tissue by the injection of 0.1 mg/kg per day risperidone. 6. These findings suggest that the materials for heat generation in white adipose tissue would be readily supplied, which in turn would reduce a storage of lipids in white adipose tissue resulting in the lower rate of bodyweight gain of rats.

Adverse effects of risperidone and haloperidol treatment in schizophrenia

PURPOSE

Side effects of pharmacological treatment in schizophrenia continue to be a major issue in spite of the development of new antipsychotics. The aim of this study is to explore the adverse effects of conventional and atypical antipsychotic drugs and their associated factors.

METHODS

Over 3 months, 41 patients with schizophrenia were randomized to treatment with risperidone 1-12 mg (n=21) or haloperidol 2-20 mg (n=20) daily. Efficacy was assessed by improvement of psychotic symptoms, measured on the Positive and Negative Syndrome Scale (PANSS). The safety and tolerability were assessed with the Extrapyramidal Symptom Rating Scale, the UKU Side-Effect Rating Scale and clinical laboratory assessments.

RESULTS

Each treatment reduced psychotic symptoms. PANSS total scores, positive scores, and general psychopathology scores declined as trial went on without significant differences between the two groups. While PANSS negative scores improved better in the risperidone group than in the haloperidol group. The tolerability of antipsychotics was statistical significantly better in the risperidone than in the haloperidol-treated patients. The most frequent adverse effects for both groups were tremor and rigidity. Antipsychotics, their doses, and hyperprolactinemia predict short-term extrapyramidal side effects. Serum prolactin levels could predict parkinsonism and dyskinesia severity. However, dyskinesia was best predicted by the doses of neuroleptics. The predictive factor of dystonia was the antipsychotic drug itself. After adjusting drug doses and concomitant medications, side effects could be markedly improved.

CONCLUSIONS

This study suggested that risperidone was superior to haloperidol in improving negative symptoms and better tolerated during the 12 weeks' treatment of schizophrenia. Serum prolactin levels could predict the severity of parkinsonism and dyskinesia.

Hepatotoxicity, leucopenia and neutropenia associated with olanzapine therapy

Hepatotoxicity, leukopenia and neutropenia are rarely associated with atypical antipsychotic drug therapy. The authors describe a case of a schizophrenic patient, who was treated twice with olanzapine, and who developed an increase of hepatic enzymes, jaundice, reduced WBC, neutropenia, and a high temperature. The patient was diagnosed as suffering from hepatocellular hepatitis, neutropenia and leucopenia. Neuroleptic treatment was discontinued immediately and the patient exhibited consequential clinical improvement. A review of the literature is included.

Atypical and conventional depot medications

The introduction of atypical antipsychotics created a therapeutic dilemma between choosing the oral novel antipsychotic or the conventional depot form. Clinicians want the advantages of both, resulting in higher levels of polypharmacy. Modern psychiatry is probably in a transitional stage from the depot culture to safer oral medications or even to a safer depot culture.

Pharmacokinetic and safety assessments of concurrent administration of risperidone and donepezil

Treatment of Alzheimer's disease sometimes uses combinations of drugs because dementia is frequently associated with behavioral symptoms. Risperidone and donepezil are both metabolized through cytochrome P450 2D6 and 3A4, raising the possibility of drug interactions with combination therapy. The objective of this study was to determine whether significant drug interactions occur with concomitant administration of donepezil and risperidone. In an open-label, three-way crossover study, 24 healthy men were randomly assigned to receive 0.5 mg of risperidone twice daily, 5 mg of donepezil once daily, or both drugs for 14 consecutive days, followed by a 21-day washout period. The treatment ratios of AUC and associated 90% confidence intervals (CIs) for risperidone active moiety, defined as risperidone plus 9-hydroxyrisperidone (ratio = 110.2%; 90% CI = 103.7-117.2), and for donepezil (ratio = 97.1%; 90% CI = 90.0-103.6) were within the 80% to 125% of bioequivalence range. The treatment ratios of Cmax and associated 90% CIs for risperidone active moiety (ratio = 114.6%; 90% CI = 107.0-122.8) and for donepezil (ratio = 96.1%; 90% CI = 90.0-102.6) were also within the bioequivalence range. Therefore, no significant pharmacokinetic differences occurred in either risperidone active moiety or donepezil when given alone or in combination. Adverse events (predominantly headache, nervousness, and somnolence) were minor and comparable for all treatment groups. The results indicate that no clinically meaningful drug interactions occurred between risperidone 1 mg daily and donepezil 5 mg daily at steady state, and therefore no dosage adjustment is required when both drugs are combined with the dosage regimen studied. Additional investigations are warranted to determine the potential for interactions in elderly patients with dementia who may eliminate risperidone and donepezil more slowly and thus be more vulnerable to clinical drug interactions than the young healthy subjects examined in this study.

Pharmacokinetic and safety assessments of galantamine and risperidone after the two drugs are administered alone and together

To explore the steady-state pharmacokinetic profile after coadministration of galantamine and risperidone, an open-label, randomized, single-center, two-way crossover drug-drug interaction study was conducted in 16 healthy elderly subjects, ages 60 years and older. The results showed that risperidone, when administered with galantamine, did not change the bioavailability of galantamine at steady state. In addition, systemic exposure of risperidone active moiety (risperidone plus 9-hydroxyrisperidone), the most clinically relevant component of risperidone treatment, was not affected by galantamine coadministration, while systemic exposure was increased by approximately 10% for risperidone and decreased by about 10% for 9-hydroxyrisperidone (active metabolite of risperidone). Galantamine and risperidone were both safe and well tolerated administered either alone or together. Thus, no dose adjustment for either risperidone orgalantamine is necessary when these two drugs are administered together in the dose range evaluated.

Peripheral injection of risperidone, an atypical antipsychotic, alters the bodyweight gain of rats

1. Risperidone is an atypical antipsychotic drug that possesses 5-hydroxytryptamine 5-HT2 receptor antagonism combined with milder dopamine D2 receptor antagonism. 2. Excessive bodyweight gain is one of the side-effects of antipsychotics. Risperidone treatment causes a greater increase in the body mass of patients than treatment with conventional antipsychotics, such as haloperidol. Therefore, the present study was undertaken in order to address the aetiology of the risperidone-induced bodyweight change in rats by examining the expression of leptin, an appetite-regulating hormone produced in white adipose tissue (WAT), and uncoupling protein (UCP)-1, a substance promoting energy expenditure in the brown adipose tissues (BAT). 3. Eight-week-old male rats were injected subcutaneously with risperidone (0.005, 0.05 or 0.5 mg/kg) twice daily for 21 days. Both bodyweight and food intake were monitored daily. On day 21, rats were decapitated and their serum leptin and prolactin concentrations were measured. Expression levels of leptin, Ucp1 and beta3-adrenoceptor (beta3-AR) genes in WAT and BAT were quantified using real-time polymerase chain reaction amplification. 4. Injection of 0.005 mg/kg risperidone into rats increased food intake and the rate of bodyweight gain, as well as the augmentation of leptin gene expression in WAT. Injection of 0.05 mg/kg risperidone increased food intake and leptin gene expression in WAT, but the rate of bodyweight gain was not affected. Injection of 0.5 mg/kg risperidone caused a reduction in bodyweight gain, as well as enhanced Ucp1 gene expression in BAT and serum prolactin concentrations. The serum leptin concentration and beta3-AR gene expression in WAT and BAT were not affected by injection of 0.5 mg/kg risperidone. 5. Although the changes in food intake observed in risperidone-injected rats were rationalized neither by serum leptin nor prolactin concentrations, the reduction in the rate of bodyweight gain following injection of 0.5 mg/kg can be explained, in part, by increased energy expenditure, as revealed by the remarkable increase in the UCP-1 mRNA expression level in BAT. The role of leptin in risperidone-induced alterations in bodyweight gain remain to be clarified.

Pharmacology and clinical experience with risperidone

Risperidone (Risperdal, Janssen Pharmaceutica) is a second generation antipsychotic (SGA) for the treatment of schizophrenia and other psychotic disorders. It is a potent antagonist of serotonin-2 (5-HT2) and dopamine-2 (D2) receptors in the brain. In comparison to conventional antipsychotics, risperidone demonstrates superior efficacy against the positive and negative symptoms of schizophrenia and a decreased occurrence of extrapyramidal side effects (EPS). Risperidone causes less weight gain than other marketed SGAs, but can increase prolactin levels and cause EPS in a dose-related manner. In a variety of pharmacoeconomic analyses, it has proven to be a cost-effective addition to the antipsychotic armamentarium. As the first SGA available for front line use, risperidone has established a new standard of care for the treatment of individuals with psychotic disorders.

The effects of olanzapine, risperidone, and haloperidol on plasma prolactin levels in patients with schizophrenia

BACKGROUND

There is relatively little comparative information on elevations in plasma prolactin level (PRL) with conventional versus novel antipsychotic agents.

OBJECTIVE

This paper examines the comparative effects on PRL of olanzapine, risperidone, and haloperidol based on data from 3 multicenter, double-blind, randomized clinical trials. Magnitude of response, dose dependency, time course, effects of sex and age, and response to switching from haloperidol to olanzapine are assessed.

METHODS

The effects of olanzapine, risperidone, and haloperidol on PRL were assessed in patients with schizophrenia or related psychoses participating in 3 double-blind clinical trials: (1) a 6-week acute trial comparing olanzapine 5 to 20 mg/d (n = 1,336) and haloperidol 5 to 20 mg/d (n = 660), with a 1-year, open-label olanzapine extension for responders; (2) a 54-week study comparing olanzapine 5 to 20 mg/d (n = 21), risperidone 4 to 10 mg/d (n = 21), and haloperidol 5 to 20 mg/d (n = 23) in early illness; and (3) a 28-week study comparing olanzapine 10 to 20 mg/d (n = 172) and risperidone 4 to 12 mg/d (n = 167).

RESULTS

PRL elevations were significantly greater with risperidone than with either olanzapine or haloperidol in study 2. and significantly greater than with olanzapine in study 3 (all, P < 0.001). PRL elevations were significantly greater with haloperidol than with olanzapine in study 1 (P < 0.001 ). A dose-response relationship was not consistently confirmed with any of the drug treatments. Risperidone-associated PRL elevations peaked relatively early in treatment. In haloperidol- and risperidone-treated patients, the mean change in PRL was greater in women than in men. PRL decreased significantly when treatment was switched from haloperidol to olanzapine.

CONCLUSIONS

This side-by-side analysis of 3 independent studies suggests that with the 3 antipsychotic drugs studied, PRL is elevated moderately by olanzapine (mean change, 1-4 ng/mL), intermediately by haloperidol (mean change, approximately 17 ng/mL), and strongly by risperidone (mean change, 45-80 ng/mL). No consistent dose-response relationship was observed, and the time course and sex-dependency of the response differed between the 3 agents. Patients with haloperidol-induced hyperprolactinemia may benefit from a switch to olanzapine. Long-term studies examining the health consequences of chronic hyperprolactinemia during antipsychotic treatment are needed.

Serum prolactin levels and sexual dysfunctions in antipsychotic medication, such as risperidone: a review

Classical antipsychotic drugs increase the level of serum prolactin. The atypical antipsychotic clozapine barely increases prolactin levels. An open naturalistic study in the University Hospital of Groningen suggests that treatment with risperidone in comparison to classical antipsychotics seems to increase the risk of erectile and ejaculatory disorders in male patients and to menstrual disturbances in female patients. In the literature reviewed, risperidone is associated with higher prolactin levels in comparison to classical antipsychotics. It is still unclear which mechanism is responsible for the increase of serum prolactin levels and sexual dysfunctions in patients using risperidone. Dopaminergic and serotonergic receptor blockade seems to play an important role. Other mechanisms are discussed.

Single- and multiple-dose pharmacokinetics of ziprasidone under non-fasting conditions in healthy male volunteers

AIMS

To evaluate the pharmacokinetics and tolerability of single and multiple oral doses of ziprasidone in healthy male volunteers, and to determine the influence of ziprasidone on serum prolactin levels.

METHODS

Single and multiple doses of ziprasidone were given orally (as two divided daily doses), at fixed dosages of 10 and 40 mg day(-1), and using titrated regimens of 40-80 and 40-120 mg day(-1), for 14 days. All dosages were taken immediately after food. The study adopted a randomized, double-blind, placebo-controlled design. Prolactin response, sedative properties, tolerability, and extrapyramidal symptoms were also investigated.

RESULTS

Steady-state exposure to ziprasidone was attained after 1 day of dosing. Mean Cmax and AUC(0,12 h) increased with increasing dose, with apparent dose-proportionality between the 20 and 60 mg dose levels. Trough-to-peak ratios at steady state ranged from 2 to 5. Accumulation ratios for the fixed-dose regimens were 1.49 and 1.48 at the 5 and 20 mg dose levels, respectively. Ziprasidone was associated with transient prolactin elevation but levels of prolactin returned to baseline within the dosing interval at steady state. There was a marginal, transient increase in serum prolactin levels which was not dose-related at the 80 and 120 mg day(-1) doses, and which was noted to attenuate with chronic dosing. Ziprasidone was generally well tolerated. The most frequent side-effect was mild or moderate headache. A minority of patients suffered first-dose postural hypotension. Ziprasidone was also associated with a mild sedative effect that became less pronounced as treatment continued. There were no drug-related changes in electrocardiogram or clinical laboratory variables that were of clinical importance.

CONCLUSIONS

Ziprasidone is characterized by a predictable pharmacokinetic profile resulting in symptoms that reflect its pharmacological action.

Dopamine receptor responsivity in schizophrenic patients before and after switch from haloperidol to risperidone

The increases that occur in plasma prolactin (PRL) levels after i.m. administration of 5 mg of haloperidol (the HAL test) provide information about the responsivity of D2 dopamine receptors in the hypothalamus-hypophysis, and may be a measure of their occupancy during the neuroleptic treatment of schizophrenic patients. We studied these responses during treatment with haloperidol (doses 7.5-60 mg daily, mean = 20.6) in 12 male schizophrenic patients who did not have a satisfactory therapeutic response to the drug, and the test was repeated 6 weeks later, after the patients were switched to therapy with the atypical neuroleptic risperidone (8-16 mg daily, mean = 11.7). After the institution of risperidone treatment, the total score on the Brief Psychiatric Rating Scale (BPRS) fell by 38% (from a mean score of 47.2 to 29.3). BPRS subscale scores for positive, negative, and general symptoms were reduced by 38, 35, and 40%, respectively. Moderate PRL responses to the HAL test were found during haloperidol treatment and no responses at all during treatment with risperidone. Baseline PRL increased significantly from a mean of 35.0 (S.D. = 16.0) to a mean of 55.7 ng/ml plasma (S.D. = 19.6). This high potency of risperidone to increase PRL levels cannot be explained by the serotonergic blocking activity of the drug, and seems not to be restricted to its D2 receptor blocking capacity.

Risperidone in treatment-refractory schizophrenia

OBJECTIVE

The purpose of this study was to evaluate the clinical safety and efficacy of risperidone compared to haloperidol in patients with treatment-refractory schizophrenia.

METHOD

Sixty-seven medication-unresponsive subjects were randomly assigned to treatment with risperidone (N = 34) or haloperidol (N = 33). After a 3-7 day-placebo washout period, there was a 4-week, double-blind, fixed-dose comparison trial that was followed by a 4-week, flexible-dose phase. Measures of clinical change were quantified by standard psychopathologic and neuromotor instruments.

RESULTS

Risperidone demonstrated clinical efficacy superior to that of haloperidol on the total Brief Psychiatric Rating Scale (BPRS) after the first 4 weeks of treatment. Risperidone did not show any advantage over haloperidol after an additional 4 weeks. Overall improvement on the BPRS at 4 weeks was significantly better for the risperidone group (24%) than for the haloperidol group (11%). Risperidone-treated subjects were significantly less likely than haloperidol-treated subjects to require concomitant anticholinergic medication after 4 weeks (20% versus 63%); they also had significantly les observable akathisia (24% versus 53%) and significantly less severe tardive dyskinesia. Baseline characteristics that correlated significantly with risperidone response were positive symptoms, conceptual disorganization, akathisia, and tardive dyskinesia.

CONCLUSIONS

Risperidone was better tolerated and more effective in a subset of patients with treatment-refractory schizophrenia. Positive psychotic symptoms and extrapyramidal side effects at baseline appear to be powerful predictors of subsequent response to risperidone.

Cognitive dysfunction in schizophrenia: a new set of tools for the assessment of cognition and drug effects

Cognitive impairment in schizophrenia must be seen as a disturbance of cortico-sub-cortical connectivity with a neurotransmitter imbalance in a circuitry system, which connects thalamic input with prefrontal processing and supplementary motor cortex and basal ganglia output. The concept of maze-solving behaviour as a continuous cognitive task evoking a conflict between prefrontal cortex and basal ganglia activity is explained and introduced to distinguish between the effects of D2 blocking agents and substances with a predominant 5HT2A receptor affinity, such as clozapine and risperidone. Complex mazes show a cognitive deficit in untreated schizophrenic patients that are impaired by conventional and improved by atypical antipsychotic substances. Processing speed improves most on clozapine, while parallel processing is best supported by the non-sedative atypical substance risperidone. Maze paradigms are presented.

A comparative review of new antipsychotics

OBJECTIVE

To review the preclinical and clinical properties of various established and putative antipsychotic medications, namely clozapine, risperidone, amisulpride, olanzapine, quetiapine, sertindole, and ziprasidone.

METHODS

This paper proposes a decision algorithm for comparing drugs used for psychotic disorders, based on biochemical profile, experimental pharmacology, postiron emission tomography (PET) scan results, and clinical efficacy on positive, negative, anxious, depressive, and cognitive symptoms. This "quotient" aims to compare the different available drugs, regardless of their development and registration status.

RESULTS

Antipsychotic drugs have been classified in many ways, mainly according to their chemical structure, clinical effects, receptor affinity, or side effects. Preclinical data have indicated that these drugs might be effective antipsychotic agents, causing fewer extrapyramidal side effects than most of the previously marketed drugs. However, the biological basis for the putative superiority of these drugs in treating psychosis has yet to be ascertained.

CONCLUSIONS

Although most antipsychotics have been shown to be at least equivalent to haloperidol on positive symptoms, they must be studied further to establish their absolute and relative efficacy on positive symptoms, negative and primary negative symptoms, cognition, psychotic anxiety, psychotic depression, suicidality, and quality of life. These drugs should be valuable in treating schizophrenia, but their merit in the long-term management of patients with schizophrenia still needs to be confirmed.

Therapeutic drug monitoring of risperidone using a new, rapid HPLC method: reappraisal of interindividual variability factors

Because of the enormous gap between premarketing studies in physically healthy subjects and clinical practice in patients, the present study reconsidered interindividual variability factors affecting risperidone concentrations under routine therapeutic drug monitoring conditions. The study included 92 patients, 27% of whom were 70 years or older. The patients received risperidone orally (dose range, 0.5-11 mg per day) and had concentrations of risperidone and the active metabolite 9-hydroxyrisperidone measured at steady state by a new, rapid, and sensitive method of high-performance liquid chromatography (HPLC). After normalization to a dose of 4 mg/day, median concentrations were 2.9 ng/ml (80% range, 0.9-27.9 ng/ml) for the parent compound and 24.1 ng/ml (80% range, 12.0-57.6 ng/ml) for the metabolite. When considering linear regression models, age was identified as a major source of interindividual variability, with expected increases of 340% and 220% for concentrations of parent compound and metabolite, with age increasing from 20 to 80 years. Body weight provided an additional significant contribution to the variability of 9-hydroxyrisperidone concentration, a 20-kg higher body weight associated with a concentration decrease of 23%. Serotonin-specific reuptake inhibitor (SSRI) comedication (fluoxetine, two patients; citalopram, two patients; paroxetine, one patient; fluvoxamine, one patient) was significantly associated with 4.6-fold higher concentrations of parent compound, in keeping with an inhibitory action on CYP2D6 enzyme. Significantly higher concentrations of 9-hydroxy-risperidone (+ 29%) were also observed in the 17 patients with biperiden comedication. Therapeutic drug monitoring data, collected in patients representative of the population for which the drug was intended, allowed us to quantify the dose reduction needed in elderly patients and thus provided valuable information in addition to the one collected during premarketing studies performed with strict inclusion and exclusion criteria.

Modulation of central serotonergic neurotransmission by risperidone: underlying mechanism(s) and significance of action

1. The effects of risperidone on brain 5-hydroxytryptamine (5-HT) neuronal activity were investigated using microdialysis in the frontal cortex (FC) or the dorsal raphe nucleus (DRN) as well as single cell recording in the DRN. 2. Systemic administration of risperidone (0.6 and 2.0 mg/kg, s.c.) dose-dependently increased 5-HT output in both the FC and the DRN. 3. Local cortical administration of both risperidone or idazoxan enhanced the 5-HT efflux in the FC, whereas local raphe administration of risperidone but not idazoxan increased the output of 5-HT in the DRN. 4. Systemic administration of risperidone (200 micrograms/kg, i.v.) or the selective alpha 1 adrenoceptor antagonist prazosin (400 micrograms/kg, i.v.) decreased, whereas selective alpha 2 adrenoceptor antagonist idazoxan (20 micrograms/kg, i.v.) increased the 5-HT cell firing in the DRN. 5. Pretreatment with the selective 5-HT1A receptor antagonist WAY 100,635 (5.0 micrograms/kg, i.v.) effectively antagonized the inhibition of 5-HT cells induced by risperidone, but failed to prevent the prazosin-induced decrease in 5-HT cell firing in the DRN. 6. The inhibitory effect of risperidone on 5-HT cell firing in the DRN was significantly attenuated in rats pretreated with the 5-HT depletor PCPA (p-chlorophenylalanine; 300 mg/kg/day i.p. for 3 consecutive days) in comparison with drug naive animals. 7. Consequently, the risperidone-induced increase in 5-HT output in the FC may be related to its alpha 2 adrenoceptor antagonistic action, an effect probably executed at the nerve terminal level, whereas the reduction in 5-HT cell firing by risperidone appears to be associated with increased availability of 5-HT in the somatodendritic region of the neurones leading to an enhanced 5-HT1A autoreceptor activation and, in turn, to inhibition of cell firing.

Effects of risperidone and SCH 23390 on isolation-induced aggression in male mice

In this study, the antiaggressive effects of risperidone and SCH 23390 have been explored. Using the paradigm of isolation-induced aggression, 150 albino male mice of the OF1 strain were allocated to control and experimental groups which received three doses of risperidone (0.01, 0.05 and 0.1 mg/kg) or two doses of SCH 23390 (0.05 and 0.1 mg/kg). Only the highest doses of risperidone decreased threat and attack behaviours but all doses significantly impaired motor behaviour. SCH 23390 decreased attack with the two doses used and also produced significant increases in immobility. Although both antipsychotics are antiaggressive, this action seems to be more specific in the case of risperidone. Finally, both drugs failed to affect animals with short attack latency, being antiaggressive only in subjects with long attack latency, which suggests that these two types of animals are different in their dopamine and serotonin neurotransmission.

Antipsychotic drug regulation of AMPA receptor affinity states and GluR1, GluR2 splice variant expression

We recently reported that chronic administration of antipsychotic drugs dramatically elevated [3H]AMPA binding, with minimal elevation of [3H]CNQX binding in rat brain. The aim of the current study was to examine the mechanism of this effect. Chronic haloperidol minimally increased the total number of binding sites (total Bmax) compared to saline-injected animals. Specifically, haloperidol dramatically increased the proportion of high-affinity-site AMPA receptors (approximately 30% increase) without inducing a significant change in the low-affinity constant. In situ hybridization for flip and flop isoforms of GluR1 and GluR2 (AMPA receptors) was not altered in a pattern or degree that compared to the changes seen in AMPA receptor binding. These findings suggest that the long-term action of antipsychotic drugs may be to regulate AMPA receptor responsiveness to agonist stimulation via posttranscriptional means, and is unlikely to be related to GluR1 or GluR2 splice variant expression. This effect may have relevance to both the therapeutic effects and side effects of antipsychotic drugs in humans.

Risperidone inhibits 5-hydroxytryptaminergic neuronal activity in the dorsal raphe nucleus by local release of 5-hydroxytryptamine

1. The effects of risperidone on brain 5-hydroxytryptamine (5-HT) neuronal functions were investigated and compared with other antipsychotic drugs and selective receptor antagonists by use of single cell recording and microdialysis in the dorsal raphe nucleus (DRN). 2. Administration of risperidone (25-400 micrograms kg-1, i.v.) dose-dependently decreased 5-HT cell firing in the DRN, similar to the antipsychotic drug clozapine (0.25-4.0 mg kg-1, i.v.), the putative antipsychotic drug amperozide (0.5-8.0 mg kg-1, i.v.) and the selective alpha 1-adrenoceptor antagonist prazosin (50-400 micrograms kg-1, i.v.). 3. The selective alpha 2-adrenoceptor antagonist idazoxan (10-80 micrograms kg-1, i.v.), in contrast, increased the firing rate of 5-HT neurones in the DRN, whereas the D2 and 5-HT2A receptor antagonists raclopride (25-200 micrograms kg-1, i.v.) and MDL 100,907 (50-400 micrograms kg-1, i.v.), respectively, were without effect. Thus, the alpha 1-adrenoceptor antagonistic action of the antipsychotic drugs might, at least partly, cause the decrease in DRN 5-HT cell firing. 4. Pretreatment with the selective 5-HT1A receptor antagonist WAY 100,635 (5.0 micrograms kg-1, i.v.), a drug previously shown to antagonize effectively the inhibition of 5-HT cells induced by risperidone, failed to prevent the prazosin-induced decrease in 5-HT cell firing. This finding argues against the notion that alpha 1-adrenoceptor antagonism is the sole mechanism underlying the inhibitory effect of risperidone on the DRN cells. 5. The inhibitory effect of risperidone on 5-HT cell firing in the DRN was significantly attenuated in rats pretreated with the 5-HT depletor PCPA (p-chlorophenylalanine; 300 mg kg-1, i.p., day-1 for 3 consecutive days) in comparison with drug naive animals. 6. Administration of risperidone (2.0 mg kg-1, s.c.) significantly enhanced 5-HT output in the DRN. 7. Consequently, the reduction in 5-HT cell firing by risperidone appears to be related to increased availability of 5-HT in the somatodendritic region of the neurones leading to an enhanced 5-HT1A autoreceptor activation and, in turn, to inhibition of firing, and is probably only to a minor extent caused by its alpha 1-adrenoceptor antagonistic action.

Extrapyramidal side effects with risperidone and haloperidol at comparable D2 receptor occupancy levels

Risperidone is an antipsychotic drug with high affinity at dopamine D2 and serotonin 5-HT2 receptors. Previous clinical studies have proposed that risperidone's pharmacologic profile may produce improved efficacy for negative psychotic symptoms and decreased propensity for extrapyramidal side effects; features shared by so-called 'atypical' neuroleptics. To determine if routine risperidone treatment is associated with a unique degree of D2 receptor occupancy and pattern of clinical effects, we used [123I]IBZM SPECT to determine D2 occupancy in subjects treated with routine clinical doses of risperidone (n = 12) or haloperidol (n = 7). Both risperidone and haloperidol produced D2 occupancy levels between approximately 60 and 90% at standard clinical doses. There was no significant difference between occupancy levels obtained with haloperidol or risperidone. Drug-induced parkinsonism was observed in subjects treated with risperidone (42%) and haloperidol (29%) and was observed at occupancy levels above 60%. Based on these observations, it is concluded that 5-HT2 blockade obtained with risperidone at D2 occupancy rates of 60% and above does not appear to protect against the risk for extrapyramidal side effects.

Risperidone in the treatment of schizophrenia: results of a study of patients from Germany, Austria, and Switzerland

Results of a subanalysis of data from the multinational risperidone trial (RIS-INT-2) are reported. Patients with chronic schizophrenia were treated with risperidone at 1 mg/day (n = 25), 4 mg/day (n = 27), 8 mg/day (n = 29), 12 mg/day (n = 31), or 16 mg/day (n = 29), or 10 mg/day of haloperidol for 8 weeks. According to the Positive and Negative Syndrome Scale (PANSS) total and subscale scores, improvements were noted in each treatment group from baseline to treatment endpoint. On each scale the magnitude of improvement was greater in the risperidone patients than in the haloperidol patients. The onset of action of risperidone was faster than haloperidol. By treatment week 2, over half of the patients receiving > or = 4 mg/day of risperidone were clinically improved (> or = 20% reduction in total PANSS scores). This rate of improvement was not seen until week 6 in the haloperidol patients. Severity of extrapyramidal symptoms (scores on the Extrapyramidal Symptom Scale) was significantly lower in patients receiving 1 or 4 mg/day of risperidone than in patients receiving higher risperidone doses and in haloperidol patients. The optimal dose of risperidone, in terms of both efficacy and safety, was 4 mg/day. These results confirm the findings of the controlled trials of risperidone conducted in North America and the multinational trial.

LSD-like panic from risperidone in post-LSD visual disorder

Risperidone, a novel antipsychotic agent, is an antagonist of postsynaptic serotonin-2 and dopamine D2 receptors. In certain individuals, the hallucinogenic drug lysergic acid diethylamide (LSD) is associated with apparently lifelong continuous visual disturbances, characterized in DSM-IV as hallucinogen-persisting perception disorder (HPPD). Because the hallucinogenic mechanism of LSD is known to act in part at postsynaptic serotonin-2 receptors, it is noteworthy that three HPPD patients treated with risperidone reported an exacerbation of LSD-like panic and visual symptoms. We conclude that HPPD may be a relative contraindication for the use of risperidone.

Pharmacokinetics of clozapine and risperidone: a review of recent literature

The current literature describing the pharmacokinetics of the atypical antipsychotics clozapine and risperidone is reviewed, and discussion on the clinical significance of these data is presented. These drugs are well absorbed when taken orally but are poorly bioavailable because of presystemic elimination. They are highly cleared by hepatic metabolism involving specific P450 isozymes. Risperidone elimination produces a potent active metabolite. Neither of the drugs has received extensive study related to drug-drug interactions, but several are potentially important because a purported therapeutic plasma concentration range is proposed for clozapine and a possible curvilinear dose response relationship has been reported for risperidone. The current clinical pharmacokinetic database for these atypical antipsychotics suggests that much can be learned with additional study that would be of value in individualizing their dosage regimens.

Risperidone: regional effects in vivo on release and metabolism of dopamine and serotonin in the rat brain

The antipsychotic drug risperidone shows high affinity for both central serotonin (5-HT)2A and dopamine (DA)-D2 receptors in vivo. By employing microdialysis in freely moving rats, the effects of acute risperidone administration on regional brain DA and 5-HT release and metabolism were compared with the corresponding effects of the atypical antipsychotic drug clozapine as well as amperozide, the selective DA-D2 receptor antagonist raclopride and the selective 5-HT2A/5-HT2C receptor antagonist ritanserin. Risperidone (0.2 or 2.0 mg/kg, SC) was found to increase DA release and metabolism to about the same extent in three major projection areas of the mesotelencephalic dopaminergic system, i.e. the nucleus accumbens (NAC), the medial prefrontal cortex (MPC) and the lateral striatum (STR). In contrast, clozapine and amperozide (both 10.0 mg/kg, SC), as well as raclopride (2.0 mg/kg, SC), were all found differentially to affect DA release and metabolism in the three projections areas. Specifically, clozapine and amperozide enhanced DA release in the MPC to a greater extent than in the NAC or the STR, whereas raclopride instead preferentially increased DA release in the NAC and the STR but not in the MPC. Ritanserin (3.0 mg/kg, SC) did not exert any major effects on DA metabolism in the three areas studied. In contrast to the regionally rather homogenous activation of brain DA systems caused by risperidone, the drug was found to enhance brain 5-HT metabolism preferentially in the MPC, as indicated by the elevated extracellular concentration of 5-hydroxyindoleacetic acid (5-HIAA) in this region. A similar elevation of the 5-HIAA level in the MPC was observed after amperozide and, to some extent, after clozapine and ritanserin administration. The risperidone-induced (2.0 mg/kg, SC) elevation of 5-HIAA concentrations in the frontal cortex was found to be paralleled by an increased 5-HT release in this brain area. Consequently, our findings demonstrate a pharmacological profile of risperidone, as reflected in brain DA metabolism, in between that of clozapine and the DA-D2 antagonists. The preferential activation of 5-HT release and metabolism in frontal cortical areas might be of particular relevance for the ameliorating effect of risperidone on negative symptoms in schizophrenia, especially when associated with depression.

Selective adenosine A2A receptor/dopamine D2 receptor interactions in animal models of schizophrenia

In the apomorphine-induced climbing mouse assay, the potencies of the selective adenosine A1 receptor agonist, N6-cyclohexyladenosine (CHA), and the selective A2A adenosine receptor agonist, 2-p-(2-carboxyethyl) phenethylamino 5'-N-ethyl-carboxamidoadenosine (CGS 21680), and various dopamine receptor antagonists were as follows: SCH 23390 = haloperidol > raclopride > CHA = CGS 21680. While in catalepsy, their potencies were SCH 23390 > haloperidol > raclopride > CGS 21680. CHA failed to induce catalepsy due to significant sedation/ataxia. The combined administration of the ED15 dose of CHA failed to potentiate the ED50 value of SCH 23390, raclopride, or haloperidol in the apomorphine-induced climbing mouse assay. However, the combined administration of the ED15 dose of CGS 21680 significantly decreased the ED50 of raclopride by 8.0-fold and haloperidol by 35-fold. The adenosine A2A receptor antagonist, 1,3,7-trimethyl-8-(3-chlorostyryl)xanthine (CSC), significantly decreased catalepsy induced by raclopride and haloperidol, while the adenosine A1 receptor antagonist, 1,3-dimethyl-8-phenylxanthine (8-PT), was ineffective. The present results show that in behavioral assays predictive for antipsychotic activity, adenosine receptor agonists block behaviors in a similar manner to dopamine receptor antagonists.

Cognitive dysfunction in schizophrenia: comparison of treatment with atypical antipsychotic agents and conventional neuroleptic drugs

Impaired cognitive function is both a feature of schizophrenia and a side effect of conventional neuroleptics. Maze tests were used to determine the effects on cognition of conventional dopamine antagonist neuroleptics (haloperidol and fluphenazine) and the newer serotonin-dopamine antagonist antipsychotics (risperidone and clozapine). Patients on clozapine or risperidone showed better performance on the maze tasks than untreated patients or patients taking conventional neuroleptics. In particular, patients treated with risperidone or clozapine were better able to maintain motor coordination while they focused on the more complex "frontal" maze tasks which required sequencing and planning. In view of the restrictions on the use of clozapine, it is suggested that risperidone should be more widely used in schizophrenia because it preserves cognitive function better than conventional neuroleptics and is therefore likely to allow patients to have better insight into their illness and to have better long-term quality of life expectations.

Behavioural interactions between 5-hydroxytryptophan, neuroleptic agents and 5-HT receptor antagonists in modifying rodent responding to aversive situations

1. The ability of 5-hydroxytryptophan, 5-HT2 receptor antagonists and typical and atypical neuroleptic agents to modify behavioural responding to aversive situations was investigated in the mouse light/dark test and rat social interaction. 2. The administration of 5-hydroxytryptophan inhibited rat social interaction and the exploratory behaviour of mice in the light/dark test. 3. The 5-HT2 receptor antagonists, ketanserin, ritanserin, MDL11939, methysergide and RP62203, the neuroleptic agents, spiperone, haloperidol and benperidol, and the atypical neuroleptic agent, clozapine, when administered alone failed to modify mouse or rat behaviour. In contrast, when administered alone, sulpiride in rats and mice and thioridazine in rats disinhibited behaviour. 4. Methysergide, RP62203, ketanserin, ritanserin and MDL11939 antagonized the inhibitory effects of 5-hydroxytryptophan or reversed the inhibitory effects to one of disinhibition. 5. Low doses of spiperone (but not haloperidol or benperidol) also antagonized the inhibitory effects of 5-hydroxytryptophan in the rat but not the mouse. Higher doses of the three neuroleptic agents caused locomotor depression in both rats and mice which obscured any specific changes in behavioural responding to the aversive situations. 6. The disinhibitory profile of sulpiride in both mice and rats and thioridazine in rats was evident during their interaction with 5-hydroxytryptophan. Thioridazine in the mouse and clozapine in rats and mice also reversed the inhibitory effects of 5-hydroxytryptophan to one of disinhibition. 7. In summary, we present evidence that the atypical neuroleptic agents, thioridazine and clozapine, with their known affinity for the 5-HT2 receptors, can mimic the actions of reference 5-HT2 receptor antagonists to antagonize the inhibitory effects of 5-hydroxytryptophan in rodent models of anxiety. The results are intepreted in terms of drug action on different 5-HT2 and other 5-HT receptor subtypes. In addition, thioridazine and sulpiride have disinhibitory effects in their own right which remain to be explained.