Chronic melperone administration does not enhance oral movements in rats

Changes in weight and body mass index during treatment with melperone, clozapine and typical neuroleptics

Melperone is an atypical antipsychotic drug that has been reported to be effective in treatment-resistant schizophrenia and L-DOPA psychosis. There are limited data concerning its effect on weight or body mass index (BMI). Weight and BMI were retrospectively compared in patients with schizophrenia treated with melperone (n=34), clozapine (n=225), or typical neuroleptics (n=74) for up to 3 months. Clozapine resulted in significant increases in weight and BMI from baseline to 6 weeks and 3 months. Neither melperone nor typical neuroleptics resulted in significant weight gain at either time point. Melperone did not result in significant increases in BMI. Weight and BMI were significantly lower with melperone compared with clozapine, but similar to typical neuroleptics. The proportion of melperone patients who experienced a >or=7% weight increase was lower than that in patients treated with clozapine and similar to that in patients treated with typical neuroleptics. Percent change in weight and BMI predicted improvement in BPRS total scores at 3 months in the clozapine group, but not in the melperone or typical neuroleptic groups. Because of the relationship between BMI and cardiovascular risk, melperone deserves further study as both a first line treatment and as an alternative to clozapine in refractory schizophrenia.

A comparison of two doses of melperone, an atypical antipsychotic drug, in the treatment of schizophrenia

Melperone at a dose of 300 mg/day has been reported to be as effective as thiothixene and superior to placebo in the treatment of schizophrenia. Limited ability to cause extrapyramidal side effects (EPS) and absence of an effect on plasma prolactin (pPRL) levels suggests that it is an atypical antipsychotic drug. The goal of this pilot study was to determine: (1). the ability of melperone 400 mg/day to produce greater improvement in psychopathology than melperone 100 mg/day; and (2). to compare side effects of these two doses of melperone. Melperone, 100 or 400 mg/day, was administered to 34 acutely hospitalized patients with schizophrenia for 6 weeks in a randomized, double-blind manner. Psychopathology, EPS, pPRL levels, and body mass index (BMI) were evaluated at baseline and 6 weeks. Twenty-seven completed the 6-week treatment. A last carried forward analysis revealed no significant difference in the ability of the two doses of melperone to improve psychopathology as measured by the Brief Psychiatric Rating Scale (BPRS)-Total and Positive subscale, the Scale for the Assessment of Negative Symptoms (SANS), the Schedule for Affective Disorders and Schizophrenia-Disorganization subscale, and the Global Assessment Scale (GAS). Treatment with melperone was not associated with exacerbation of EPS, or an increase in pPRL levels or BMI. The Abnormal Involuntary Movement Scale (AIMS) was not significantly changed by treatment with melperone. These results suggest that melperone was equally effective at doses 100 and 400 mg/day, for ameliorating psychopathology and improving overall psychiatric status in patients with schizophrenia. However, the lack of difference and a placebo control group, as well as modest degrees of change in psychopathology, require caution about assuming efficacy of either dose. The lack of significant side effects such as exacerbation of EPS, pPRL elevation, and weight gain indicates melperone is well tolerated.

The vacuous chewing movement (VCM) model of tardive dyskinesia revisited: is there a relationship to dopamine D(2) receptor occupancy?

Tardive dyskinesia (TD) is a late side effect of long-term antipsychotic use in humans, and the vacuous chewing movement (VCM) model has been used routinely to study this movement disorder in rats. Recent receptor occupancy studies in humans and rats have found that antipsychotics given in doses which lead to moderate levels of D(2) receptor blockade can achieve optimal clinical response while minimizing the emergence of acute motor side effects. This suggests that clinicians may have been using inappropriately high doses of antipsychotics. A review of the existing VCM literature indicates that most animal studies have similarly employed antipsychotic doses that are high, i.e. doses that lead to near complete D(2) receptor saturation. To verify whether the incidence or severity of VCMs would decrease with lower antipsychotic doses, we conducted initial experiments with different doses of haloperidol (HAL) given either as repeated daily injections or as depot injections over the course of several weeks. Our results demonstrate that (1) the incidence of VCMs is significantly related to HAL dose, and (2) significant levels of VCMs only emerge when haloperidol is continually present. These findings are consistent with the possibility that total D(2) occupancy, as well as 'transience' of receptor occupation, may be important in the development of late-onset antipsychotic-induced dyskinetic syndromes.

Melperone in the treatment of neuroleptic-resistant schizophrenia

Melperone is an effective antipsychotic drug that has been reported to have atypical properties, i.e. low extrapyramidal side effect liability at clinically effective doses. It also does not increase serum prolactin levels. Its effectiveness for patients with neuroleptic (treatment)-resistant schizophrenia has not been evaluated. In this study, melperone was administered, in an open trial design of 6 weeks' duration, to 44 patients with chronic neuroleptic-resistant schizophrenia. The Global Assessment Scale (GAS), Brief Psychiatric Rating Scale (BPRS) and measures of extrapyramidal symptoms and other clinical variables were assessed at baseline and 6 weeks. Thirty-seven patients completed the 6-week trial. Melperone significantly improved overall psychiatric status as measured by GAS score for all evaluable subjects [last value carried forward (LVCF) and a completers analysis]. No significant effects on BPRS measures of psychopathology scores were found in the LVCF or completers analysis. Patients who showed > or = 20% decrease in the BPRS Total score (N=7) were more likely to have high baseline psychopathology, as measured by BPRS Total and Anxiety-Depression subscales, than those who showed > or = 20% increase in the BPRS Total score (N=8). Non-responders to melperone generally did not respond to subsequent treatment with clozapine, indicating that this group of patients was very treatment resistant. Melperone was not associated with worsening of extrapyramidal symptoms, elevation in plasma prolactin levels, or an increase in body mass index (BMI). The results suggest that a proportion of neuroleptic-resistant patients with schizophrenia respond to melperone, which requires further controlled study.

The effects of raclopride on vacuous jaw movements in rats following acute administration

Classic neuroleptics produce a syndrome of vacuous jaw movements in rats, whereas atypical neuroleptics like clozapine do not. The present study compared the effects of repeated administration of raclopride, clozapine, haloperidol, or vehicle on vacuous jaw movements in rats over a 4-week period. Rats received an IP injection of drug once a day. On days 1, 8, 15, and 29 the rats were observed for a 5-min period by two trained observers who recorded their vacuous jaw movements. The dose-response curves at which each drug produced vacuous jaw movements are presented and discussed in terms of their predictive capabilities of early onset extrapyramidal side effects.

High frequency oral movements induced by long-term administration of amperozide but not FG5803 in rats

Long-term studies of antipsychotic-induced oral movements may serve as a rat model of acute and tardive movement disorders. Vacuous chewing movements (VCM), tongue protrusions (TP), and jaw tremors (TR) were studied in rats during acute and chronic administration of two potential antipsychotics, amperozide and FG5803. Comparisons were made with haloperidol and vehicle. Single intraperitoneal injections of amperozide (0.2, 1, or 5 mg/kg) or FG5803 (1.2, 6, or 30 mg/kg) were without effect on oral behaviors. During long-term drug administration, withdrawal and readministration, endpoint analysis was focused on changes in supranormal oral movements. The maximal mean control frequencies found at 29 sessions during 14 months experiment +2 standard deviations were used to define the upper limit of the normal range. FG5803 (1.2, 6, or 30 mg/kg per day) administered via the drinking water for 12 months, did not produce significant deviations from this normal range with respect to VCM, TP, or TR, and this drug was not studied further. Rats receiving amperozide (0.2, 1, or 5 mg/kg per day) showed dose-related increases in oral movements over the year. The changes began after 3 months of treatment with amperozide 1 and 5 mg/kg per day, but became statistically significant only during the second half of the treatment year. Amperozide 0.2 mg/kg per day did not produce significant changes in oral movements during administration for a year, but drug withdrawal resulted in a significant rise in TP behavior. Haloperidol (1 mg/kg per day) produced increases in supranormal oral movements which tended to level out after 9 months. In all groups with significant elevations (i.e. haloperidol and amperozide 1 and 5 mg/kg per day), there was a persistence of such movements during a month of drug withdrawal. During treatment with amperozide (1 or 5 mg/kg per day), some rats developed a high frequency chewing behavior up to 175 VCMs/min. It is concluded that long-term treatment with amperozide, but not FG5803, produced a tardive pattern of supranormal oral movements. The importance of these findings for the clinical future of amperozide is difficult to predict, due to the unexpected finding of high-frequency chewing, which has not been noticed before during extensive studies of classical neuroleptics.