Differential effects of the antipsychotics haloperidol and clozapine on G protein measures in mononuclear leukocytes of patients with schizophrenia

AIMS: Heterotrimeric G proteins play a pivotal role in postreceptor information transduction. These proteins were previously implicated in the pathophysiology and treatment of mood and other neuropsychiatric disorders. Recently we showed that untreated patients with schizophrenia have a significantly elevated dopamine-induced Gs protein function which is correlated with the severity of the psychotic symptoms. In contrast, an inverse picture with reduction in the function and the immunoreactivity of Gs protein was detected in patients with Parkinson's disease. The present study aims at investigating the effect of antipsychotic medications on dopamine-induced Gs protein hyperfunction in schizophrenia comparing the classical antipsychotic haloperidol and the newer antipsychotic clozapine, which is devoid of extrapyramidal side effects, on G protein measures. METHODS: G protein functional measurements coupled to beta-adrenergic, muscarinic, and dopamine receptors were undertaken through bacterial toxin sensitive, agonist enhanced [3H]-Gpp(NH)p binding capacity, substantiated by quantitative measures of Gs alpha, Gi alpha, and G beta subunit proteins through immunoblot analysis in mononuclear leukocytes obtained from patients with schizophrenia under haloperidol, or clozapine treatments in comparison with untreated patients with schizophrenia and healthy volunteers. RESULTS: Dopamine-induced Gs hyperfunction characteristic of untreated patients with schizophrenia was not detected under antipsychotic treatment with either haloperidol or clozapine. Haloperidol caused a significant decrease in Gs function and immunoreactivity below normal levels. The extend of reduction in Gs function was found to be correlated with the intensity of extrapyramidal side effects. The pattern of G protein subunits levels in patients with schizophrenia under haloperidol treatment resembles the one obtained in patients with Parkinson's disease. CONCLUSIONS: In the present study it is shown that G protein measurements in patients with schizophrenia under antipsychotic treatments can be used to biochemically monitor effects of antipsychotic medications in living patients. Moreover, these measurements may be used also for monitoring parkinsonian side effects induced by antipsychotic medications.     

Medication nonadherence: an unrecognized cardiovascular risk factor

Nonadherence with prescribed drug regimens is a pervasive medical problem. Multiple variables affecting physicians and patients contribute to nonadherence, which negatively affects treatment outcomes. In patients with hypertension, medication nonadherence is a significant, often unrecognized, risk factor that contributes to poor blood pressure control, thereby contributing to the development of further vascular disorders such as heart failure, coronary heart disease, renal insufficiency, and stroke. Analysis of various patient populations shows that choice of drug, use of concomitant medications, tolerability of drug, and duration of drug treatment influence the prevalence of nonadherence. Intervention is required among patients and healthcare prescribers to increase awareness of the need for improved medication adherence. Within this process, it is important to identify indicators of nonadherence within patient populations. This review examines the prevalence of nonadherence as a risk factor in the management of chronic diseases, with a specific focus on antihypertensive medications. Factors leading to increased incidence of nonadherence and the strategies needed to improve adherence are discussed. Medication nonadherence, defined as a patient's passive failure to follow a prescribed drug regimen, remains a significant concern for healthcare professionals and patients. On average, one third to one half of patients do not comply with prescribed treatment regimens.[1-3] Nonadherence rates are relatively high across disease states, treatment regimens, and age groups, with the first several months of therapy characterized by the highest rate of discontinuation.[3] In fact, it has recently been reported that low adherence to beta-blockers or statins in patients who have survived a myocardial infarction results in an increased risk of death.[4] In addition to inadequate disease control, medication nonadherence results in a significant burden to healthcare utilization - the estimated yearly cost is $396 to $792 million.[1] Additionally, between one third and two thirds of all medication-related hospital admissions are attributed to nonadherence.[5,6]Cardiovascular disease, which accounts for approximately 1 million deaths in the United States each year, remains a significant health concern.[7] Risk factors for the development of cardiovascular disease are associated with defined risk-taking behaviors (eg, smoking), inherited traits (eg, family history), or laboratory abnormalities (eg, abnormal lipid panels).[7] A significant but often unrecognized cardiovascular risk factor universal to all patient populations is medication nonadherence; if a patient does not regularly take the medication prescribed to attenuate cardiovascular disease, no potential therapeutic gain can be achieved. Barriers to medication adherence are multifactorial and include complex medication regimens, convenience factors (eg, dosing frequency), behavioral factors, and treatment of asymptomatic conditions.[2] This review highlights the significance of nonadherence in the treatment of hypertension, a silent but life-threatening disorder that affects approximately 72 million adults in the United States.[7] Hypertension often develops in a cluster with insulin resistance, obesity, and hypercholesterolemia, which contributes to the risk imposed by nonadherence with antihypertensive medications. Numerous strategies to improve medication adherence are available, from enhancing patient education to providing medication adherence information to the healthcare team and will be discussed in this article.     

精神分裂症患者中的高泌乳素血症研究进展

高泌乳素血症在精神分裂症患者中发生率高,主要原因为抗精神病药物和精神分裂症本身的作用。精神分裂症患者服用抗精神病药物后泌乳素水平较快升高,长期服用后泌乳素水平可能趋向于稳定甚至降低,但仍高于正常值。高泌乳素血症会导致肥胖等诸多不良后果。而精神分裂症患者服用抗精神病药物后另一常见的副反应是代谢相关不良反应,越来越多的研究开始关注兼顾治疗高泌乳素血症及肥胖、糖脂代谢异常的方法。溴隐亭、阿立哌唑及芍药甘草汤等中药具有一定的降低泌乳素水平的作用,但使用有限制性,且不能改善抗精神病药物所致代谢相关的不良反应。二甲双胍除了能改善糖脂代谢紊乱,还具有潜在的降泌乳素作用,对于同时有代谢异常如肥胖、糖脂代谢异常及高泌乳素血症的患者来说可能具有双重治疗效果,但其降泌乳素的疗效和剂量需要进一步的大样本临床研究。     

Muscarinic receptors: do they have a role in the pathology and treatment of schizophrenia?

The high affinity of antipsychotic drugs for the dopamine D2 receptor focused attention onto the role of these receptors in the genesis of psychoses and the pathology of schizophrenia. However, psychotic symptoms are only one aspect of the complex symptom profile associated with schizophrenia. Therefore, research continues into other neurochemical systems and their potential roles in key features associated with schizophrenia. Modulating the cholinergic system in attempts to treat schizophrenia predates specific neurochemical hypotheses of the disorder. Cholinergic modulation has progressed from the use of coma therapy, through the use of anti-cholinergic drugs to control side-effects of older (typical) antipsychotic medications, to the development of drugs designed to specifically activate selected muscarinic receptors. This review presents data implicating a decrease in muscarinic receptors, particularly the M1 receptor, in the pathology of schizophrenia and explores the potential physiological consequences of such a change, drawing on data available from muscarinic receptor knockout mice as well as clinical and pre-clinical pharmacology. The body of evidence presented suggests that deficits in muscarinic receptors are associated with some forms of schizophrenia and that targeting these receptors could prove to be of therapeutic benefit to patients with the disorder.     

Prise en charge du premier épisode psychotique : le patient partenaire

Early recognition and effective management of the first episode of psychosis in a patient with schizophrenia or schizoaffective disorder is key in preventing further psychotic episodes. Patients’ denial of illness makes it difficult to establish early diagnosis and makes them unwilling to accept treatment after first episodes of psychosis. Many different reasons lead to poor compliance, resulting in high relapse rates within five years of recovery from the first episode, the risk of suicide, increased risk of violence, and increased impairment of occupational and social functioning. Second generation antipsychotic drugs prescribed at the early stages of illness represents a major advancement in the management of schizophrenia, with a lower propensity to develop extrapyramidal symptoms and tardive dyskinesia. These agents have become the preferred treatment option in most patients. Low doses of these medications at the early stages of the illness appear to help patients accept their illnesses better in the medium and long terms. Long-acting injectable formulations of atypical antipsychotic drugs (long-acting risperidone injection) offer the benefit of the efficacy and tolerance of the newer agents, together with the security of consistent delivery. This new potential treatment option for first-episode psychosis patients is the focus of this review. However, the advantages of such formulations clearly depend on patient acceptance of an injection and family support. Therefore, the attitude of the medical team impacts the patient’s attitude toward the injection. More attention must be focused on user and provider attitudes as well as treatment satisfaction. However, important issues must still be addressed, including the need for better solutions that address treatment non-compliance.     

What is the risk‐benefit ratio of long‐term antipsychotic treatment in people with schizophrenia?

The long‐term benefit‐to‐risk ratio of sustained antipsychotic treatment for schizophrenia has recently been questioned. In this paper, we critically examine the literature on the long‐term efficacy and effectiveness of this treatment. We also review the evidence on the undesired effects, the impact on physical morbidity and mortality, as well as the neurobiological correlates of chronic exposure to antipsychotics. Finally, we summarize factors that affect the risk‐benefit ratio. There is consistent evidence supporting the efficacy of antipsychotics in the short term and mid term following stabilization of acute psychotic symptoms. There is insufficient evidence supporting the notion that this effect changes in the long term. Most, but not all, of the long‐term cohort studies find a decrease in efficacy during chronic treatment with antipsychotics. However, these results are inconclusive, given the extensive risk of bias, including increasing non‐adherence. On the other hand, long‐term studies based on national registries, which have lower risk of bias, find an advantage in terms of effectiveness during sustained antipsychotic treatment. Sustained antipsychotic treatment has been also consistently associated with lower mortality in people with schizophrenia compared to no antipsychotic treatment. Nevertheless, chronic antipsychotic use is associated with metabolic disturbance and tardive dyskinesia. The latter is the clearest undesired clinical consequence of brain functioning as a potential result of chronic antipsychotic exposure, likely from dopaminergic hypersensitivity, without otherwise clear evidence of other irreversible neurobiological changes. Adjunctive psychosocial interventions seem critical for achieving recovery. However, overall, the current literature does not support the safe reduction of antipsychotic dosages by 50% or more in stabilized individuals receiving adjunctive psychosocial interventions. In conclusion, the critical appraisal of the literature indicates that, although chronic antipsychotic use can be associated with undesirable neurologic and metabolic side effects, the evidence supporting its long‐term efficacy and effectiveness, including impact on life expectancy, outweighs the evidence against this practice, overall indicating a favorable benefit‐to‐risk ratio. However, the finding that a minority of individuals diagnosed initially with schizophrenia appear to be relapse free for long periods, despite absence of sustained antipsychotic treatment, calls for further research on patient‐level predictors of positive outcomes in people with an initial psychotic presentation.     

Glutamate and Schizophrenia: Beyond the Dopamine Hypothesis

1. After 50 years of antipsychotic drug development focused on the dopamine D2 receptor, schizophrenia remains a chronic, disabling disorder for most affected individuals.2. Studies over the last decade demonstrate that administration of low doses of NMDA receptor antagonists can cause in normal subjects the negative symptoms, cognitive impairments and physiologic disturbances observed in schizophrenia.3. Furthermore, a number of recently identified risk genes for schizophrenia affect NMDA receptor function or glutamatergic neurotransmission.4. Placebo-controlled trials with agents that directly or indirectly activate the glycine modulatory site on the NMDA receptor have shown reduction in negative symptoms, improvement in cognition and in some cases reduction in positive symptoms in schizophrenic patients receiving concurrent antipsychotic medications.5. Thus, hypofunction of the NMDA receptor, possibly on critical GABAergic inter-neurons, may contribute to the pathophysiology of schizophrenia.     

Reappraising the variability of effects of antipsychotic medication in schizophrenia: a meta‐analysis

It is common experience for practising psychiatrists that individuals with schizophrenia vary markedly in their symptomatic response to antipsychotic medication. What is not clear, however, is whether this variation reflects variability of medication‐specific effects (also called “treatment effect heterogeneity”), as opposed to variability of non‐specific effects such as natural symptom fluctuation or placebo response. Previous meta‐analyses found no evidence of treatment effect heterogeneity, suggesting that a “one size fits all” approach may be appropriate and that efforts at developing personalized treatment strategies for schizophrenia are unlikely to succeed. Recent advances indicate, however, that earlier approaches may have been unable to accurately quantify treatment effect heterogeneity due to their neglect of a key parameter: the correlation between placebo response and medication‐specific effects. In the present paper, we address this shortcoming by using individual patient data and study‐level data to estimate that correlation and quantitatively characterize antipsychotic treatment effect heterogeneity in schizophrenia. Individual patient data (on 384 individuals who were administered antipsychotic treatment and 88 who received placebo) were obtained from the Yale University Open Data Access (YODA) database. Study‐level data were obtained from a meta‐analysis of 66 clinical trials including 17,202 patients. Both individual patient and study‐level analyses yielded a negative correlation between placebo response and treatment effect for the total score on the Positive and Negative Syndrome Scale (PANSS) (ρ=–0.32, p=0.002 and ρ=–0.39, p<0.001, respectively). Using the most conservative of these estimates, a meta‐analysis of treatment effect heterogeneity provided evidence of a marked variability in antipsychotic‐specific effects between individuals with schizophrenia, with the top quartile of patients experiencing beneficial treatment effects of 17.7 points or more on the PANSS total score, while the bottom quartile presented a detrimental effect of treatment relative to placebo. This evidence of clinically meaningful treatment effect heterogeneity suggests that efforts to personalize antipsychotic treatment of schizophrenia have potential for success.     

Decreased Chloride Channel Expression in the Dorsolateral Prefrontal Cortex in Schizophrenia

Alterations in GABAergic neurotransmission are implicated in several psychiatric illnesses, including schizophrenia. The Na-K-Cl and K-Cl cotransporters regulate intracellular chloride levels. Abnormalities in cotransporter expression levels could shift the chloride electrochemical gradient and impair GABAergic transmission. In this study, we performed Western blot analysis to investigate whether the Na-K-Cl and K-Cl cotransporter protein is abnormally expressed in the dorsal lateral prefrontal cortex and the anterior cingulate cortex in patients with schizophrenia versus a control group. We found decreased K-Cl cotransporter protein expression in the dorsal lateral prefrontal cortex, but not the anterior cingulate cortex, in subjects with schizophrenia, supporting the hypothesis of region level abnormal GABAergic function in the pathophysiology of schizophrenia. Subjects with schizophrenia off antipsychotic medication at the time of death had decreased K-Cl cotransporter protein expression compared to both normal controls and subjects with schizophrenia on antipsychotics. Our results provide evidence for KCC2 protein abnormalities in schizophrenia and suggest that antipsychotic medications might reverse deficits of this protein in the illness.     

Longitudinal Changes in Total Brain Volume in Schizophrenia: Relation to Symptom Severity,Cognition and Antipsychotic Medication

Studies show evidence of longitudinal brain volume decreases in schizophrenia. We studied brain volume changes and their relation to symptom severity, level of function, cognition, and antipsychotic medication in participants with schizophrenia and control participants from a general population based birth cohort sample in a relatively long follow-up period of almost a decade. All members of the Northern Finland Birth Cohort 1966 with any psychotic disorder and a random sample not having psychosis were invited for a MRI brain scan, and clinical and cognitive assessment during 1999–2001 at the age of 33–35 years. A follow-up was conducted 9 years later during 2008–2010. Brain scans at both time points were obtained from 33 participants with schizophrenia and 71 control participants. Regression models were used to examine whether brain volume changes predicted clinical and cognitive changes over time, and whether antipsychotic medication predicted brain volume changes. The mean annual whole brain volume reduction was 0.69% in schizophrenia, and 0.49% in controls (p = 0.003, adjusted for gender, educational level, alcohol use and weight gain). The brain volume reduction in schizophrenia patients was found especially in the temporal lobe and periventricular area. Symptom severity, functioning level, and decline in cognition were not associated with brain volume reduction in schizophrenia. The amount of antipsychotic medication (dose years of equivalent to 100 mg daily chlorpromazine) over the follow-up period predicted brain volume loss (p = 0.003 adjusted for symptom level, alcohol use and weight gain). In this population based sample, brain volume reduction continues in schizophrenia patients after the onset of illness, and antipsychotic medications may contribute to these reductions.     

Interactions between estradiol and haloperidol on perseveration and reversal learning in amphetamine-sensitized female rats

There are sex differences associated with schizophrenia, as women exhibit later onset of the disorder, less severe symptomatology, and better response to antipsychotic medications. Estrogens are thought to play a role in these sex differences; estrogens facilitate the effects of antipsychotic medications to reduce the positive symptoms of schizophrenia, but it remains unclear whether estrogens protect against the cognitive symptoms of this disorder. Amphetamine sensitization is used to model some symptoms of schizophrenia in rats, including cognitive deficits like excessive perseveration and slower reversal learning. In this experiment female rats were administered a sensitizing regimen of amphetamine to mimic these cognitive symptoms. They were ovariectomized and administered either low or high estradiol replacement as well as chronic administration of the antipsychotic haloperidol, and were assessed in tests of perseveration and reversal learning. Results of these experiments demonstrated that, in amphetamine-sensitized rats, estradiol alone does not affect perseveration or reversal learning. However, low estradiol facilitates a 0.25 mg/day dose of haloperidol to reduce perseveration and improve reversal learning. Combined high estradiol and 0.25 mg/day haloperidol has no effect on perseveration or reversal learning, but high estradiol facilitates the effects of 0.13 mg/day haloperidol to reduce perseveration and improve reversal learning. Thus, in amphetamine-sensitized female rats, 0.25 mg/day haloperidol only improved perseveration and reversal learning when estradiol was low, while 0.13 mg/day haloperidol only improved these cognitive processes when estradiol was high. These findings suggest that estradiol facilitates the effects of haloperidol to improve perseveration and reversal learning in a dose-dependent manner.     

Adjunctive aripiprazole decreased metabolic side effects of clozapine treatment

Clozapine is an atypical antipsychotic indicated for the treatment of refractory schizophrenia. Clozapine treatment is associated with the metabolic side effects. Weight gain, hyperlipidemia and hyperglycemia are the risk factors for onset of diabetes and cardiovascular disorders. We report a case vignette of a patient in whom the decrease in negative and general psychopathology after adjunctive aripiprazole appeared simultaneously with a reduction of clozapine-induced increase in weight and metabolic measures. Combined application of clozapine and aripiprazole is in accordance with a neurobiological rationale and appears to be a safe and well tolerated.     

Adolescent Risperidone treatment alters protein expression associated with protein trafficking and cellular metabolism in the adult rat prefrontal cortex

The prefrontal cortex (PFC) is associated with mental health illnesses including schizophrenia, depression, bipolar disorder, and autism spectrum disorders. It richly expresses neuroreceptors which are the target for antipsychotics. However, as the precise mechanism of action of antipsychotic medications is not known, proteomic studies of the effects of antipsychotic drugs on the brain are warranted. In the current study, we aimed to characterize protein expression in the adult rodent PFC (n = 5 per group) following low‐dose treatment with Risperidone or saline in adolescence (postnatal days 34–47). The PFC was examined by triplicate 1 h runs of label‐free LC‐MS/MS. The raw mass spectral data were analyzed with the MaxQuant^TM software. Statistical analysis was carried out using SAS® Version 9.1. Pathway and functional analysis was performed with IngenuityPathway Analysis and in the Database for Annotation, Visualization and Integrated Discovery (DAVID), respectively, the most implicated pathways were found to be related to mitochondrial function, protein trafficking, and the cytoskeleton. This report adds to the current repertoire of data available concerning the effects of antipsychotic drugs on the brain and sheds light on their biological mechanisms. The MS data have been deposited with the ProteomeXchange Consortium with dataset identifier PXD000480.     

A Specific Effect of Antipsychotic Drugs on Protein Synthesis in Human Lymphomononuclear Cells

We have studied the effects of psychotropic drugs on patterns of protein synthesis in human lymphomononuclear cells by two-dimensional gel electrophoretic analysis. Drugs effective in treatment of schizophrenia specifically increased the relative synthesis of a 30-kDa polypeptide in cultured human lymphomononuclear cells whereas dopamine (DA) or psychoactive drugs lacking antipsychotic properties did not. The effect was stereospecific with respect to the clinically active and inactive isomers of flupenthixol. Synthesis of the 30-kDa polypeptide appears therefore to be correlated with antipsychotic properties but not with DA receptor binding. It is possible that such effects may be associated with the clinically beneficial effect of antipsychotic drugs in the brain.     

The role of glutamate receptors in antipsychotic drug action

Summary. It has recently been postulated that disturbances in glutamatergic neurotransmission may contribute to the pathophysiology of schizophrenia. Therefore the aim of the present study was to evaluate the role of glutamate NMDA and group II metabotropic receptors in the antipsychotic drug action. To this aim the influence of some well-known neuroleptics on cortical NMDA receptors was examined. Furthermore, their behavioral effects were compared with those of the novel agonist of group II glutamate metabotropic receptors, LY 354740, in some animal models of schizophrenic deficits. We found that long-term administration of the typical neuroleptic haloperidol and the atypical one clozapine increased the number of NMDA receptors labelled with [³H]CGP 39653 in different cortical areas. Long-, but not short-term, treatment with haloperidol and raclopride diminished the deficit of prepulse inhibition produced by phencyclidine, which is a model of sensorimotor gating deficit in schizophrenia. In contrast, neither short- nor long-term treatment with clozapine influenced the phencyclidine effect in that model. Acute treatment with LY 354740 reversed neither (1) the deficit of prepulse inhibition produced by phencyclidine or apomorphine, nor (2) the impairment in a delayed alternation task induced by MK-801, which is commonly used to model the frontal lobe deficits associated with schizophrenia. The present study suggests that an increase in the density of cortical NMDA receptors may be important to a longterm neuroleptic therapy. Conversely, the results do not support the role of group II metabotropic glutamate receptors in the antipsychotic drug action. Received August 31, 1999 Accepted September 20, 1999     

Antipsychotic drugs increase N-acetylaspartate and N-acetylaspartylglutamate in SH-SY5Y human neuroblastoma cells

N -Acetylaspartate (NAA) and N -acetylaspartylglutamate (NAAG) are related neuronal metabolites associated with the diagnosis and treatment of schizophrenia. NAA is a valuable marker of neuronal viability in magnetic resonance spectroscopy, a technique which has consistently shown NAA levels to be modestly decreased in the brains of schizophrenia patients. However, there are conflicting reports on the changes in brain NAA levels after treatment with antipsychotic drugs, which exert their therapeutic effects in part by blocking dopamine D₂ receptors. NAAG is reported to be an agonist of the metabotropic glutamate 2/3 receptor, which is linked to neurotransmitter release modulation, including glutamate release. Alterations in NAAG metabolism have been implicated in the development of schizophrenia possibly via dysregulation of glutamate neurotransmission. In the present study we have used high performance liquid chromatography to determine the effects of the antipsychotic drugs haloperidol and clozapine on NAA and NAAG levels in SH-SY5Y human neuroblastoma cells, a model system used to test the responses of dopaminergic neurons in vitro . The results indicate that the antipsychotic drugs haloperidol and clozapine increase both NAA and NAAG levels in SH-SY5Y cells in a dose and time dependant manner, providing evidence that NAA and NAAG metabolism in neurons is responsive to antipsychotic drug treatment.     

Regional Abnormality of Grey Matter in Schizophrenia: Effect from the Illness or Treatment?

Both schizophrenia and antipsychotic treatment are known to modulate brain morphology. However, it is difficult to establish whether observed structural brain abnormalities are due to disease or the effects of treatment. The aim of this study was to investigate the effects of illness and antipsychotic treatment on brain structures in antipsychotic-naïve first-episode schizophrenia based on a longitudinal short-term design. Twenty antipsychotic-naïve subjects with first-episode schizophrenia and twenty-four age- and sex-matched healthy controls underwent 3T MRI scans. Voxel-based morphometry (VBM) was used to examine the brain structural abnormality in patients compared to healthy controls. Nine patients were included in the follow-up examination after 8 weeks of treatment. Tensor-based morphometry (TBM) was used to identify longitudinal brain structural changes. We observed significantly reduced grey matter volume in the right superior temporal gyrus in antipsychotic-naïve patients with schizophrenia compared with healthy controls. After 8 weeks of treatment, patients showed significantly increased grey matter volume primarily in the bilateral prefrontal cortex, insula, right thalamus, left superior occipital cortex and the bilateral cerebellum. In addition, a greater enlargement of the prefrontal cortex is associated with the improvement in negative symptoms, and a more enlarged thalamus is associated with greater improvement in positive symptoms. Our results suggest the following: (1) the abnormality in the right superior temporal gyrus is present in the early stages of schizophrenia, possibly representing the core region related to schizophrenia; and (2) atypical antipsychotics could modulate brain morphology involving the thalamus, cortical grey matter and cerebellum. In addition, examination of the prefrontal cortex and thalamus might facilitate an efficient response to atypical antipsychotics in terms of symptom improvement.     

Pharmacologic features and effects of neuroleptics.

Neuroleptic drugs reduce the severity and prevent the recurrence of symptoms of schizophrenia. Recent studies indicate that these drugs probably produce their antipsychotic effects by blocking dopamine receptors in the brain, although they also block acetylcholine and norepinephrine receptors. The potency of commercially available neuroleptics in blocking dopamine receptors varies widely, being related to the compound''s lipid solubility. Neuroleptics predispose the patient to short-term and long-term medical hazards that must be weighed against the benefits of reduced symptom intensity, shortened psychotic episodes and lessened likelihood of recurrence of acute schizophrenic epidoses. The side effects associated with short-term therapy are either extremely rare or are treatable by dose change, medication change or the use of additional drugs. In long-term therapy the risks are more problematic in that they are sometimes irreversible. These include tardive dyskinesia, skin discoloration and corneal deposits. The clinician must consider the pattern aand severity of each patient''s present and past psychotic episodes before deciding whether maintenance therapy with neuroleptics is justified. If it is, doses should be re-evaluated frequently and kept as low as possible. Concomitant administration of anticholinergic agents should be avoided if possible. Most important, the long-term administration of neuroleptics should be prescribed only for patients with schizophrenia and not for those with conditions that respond to other treatments.     

Structural contributions of antipsychotic drugs to their therapeutic profiles and metabolic side effects

Antipsychotic drugs have various neuropharmacological properties as a result of their structural diversity. Despite their therapeutic benefits, most of the prescribed atypical antipsychotics can induce severe side effects, including weight gain, type II diabetes mellitus, and cardiovascular diseases. Among the developed atypical antipsychotic agents, tetracyclic dibenzodiazepine and thienobenzodiazepine compounds, particularly clozapine and olanzapine, are associated with the greatest weight gain and metabolic disturbances. However, the unique chemical structure of these compounds causes the low risk of side effects reported for typical antipsychotics (e.g. extrapyramidal symptoms and tardive dyskinesia). This report reviews the recent discovery of the potential role of the chemical structure of antipsychotics in their therapeutic properties and metabolic disturbances. By developing structure-activity relationship studies for atypical antipsychotics, we will improve our understanding of the structural modifications of these chemical classes that lead to reduced weight gain, which will be an invaluable step toward the discovery of the next generation of atypical antipsychotics. In this review, we suggest that a novel dibenzodiazepine or thienobenzodiazepine antipsychotic drug with lower affinity for H(1) receptors may significantly advance schizophrenia therapy.