Extrapyramidal symptoms during treatment of first schizophrenia episode: Results from EUFEST

The European First Episode Schizophrenia Trial (EUFEST) included first-episode schizophrenia patients, assessing the efficacy of five antipsychotic drugs (haloperidol, amisulpride, olanzapine, quetiapine and ziprasidone) over one year. Baseline frequency of extrapyramidal symptoms (EPS) in this group of patients (n=490) was as follows: parkinsonism 10.8%, akathisia 10.0%, dystonia 1.8%, and dyskinesia 0.6%. The frequency of parkinsonism at baseline was greater in patients with a brief prior exposure to antipsychotics (≤2 weeks) compared with antipsychotic-naïve ones, and was positively correlated with the intensity of negative symptoms and negatively with depressive symptoms. After one month of treatment, the increase of parkinsonism was highest in patients receiving haloperidol (+13%), that of akathisia in patients treated with ziprasidone (+14%), and 10.1% of the patients were taking anticholinergic drugs, most frequently in the haloperidol group (24%). In 291 patients remaining on treatment after one year, both parkinsonism and akathisia had decreased: the frequency of parkinsonism was 3%, highest in the haloperidol group (9.1%), that of akathisia was 3%, highest in the quetiapine group (7.5%), and 4% of patients were taking anticholinergic drugs, most frequently those receiving haloperidol (10.5%). The results obtained suggest that in first-episode schizophrenia patients during the first year of antipsychotic treatment (in this case amisulpride, haloperidol in low doses, olanzapine, quetiapine and ziprasidone), EPS were present as manageable clinical problems.     

Clozapine versus typical antipsychotics a retro- and prospective study of extrapyramidal side effects

Schizophrenic patients in long-term neuroleptic monotherapy with clozapine (n=100) and perphenazine, flupenthixol or zuclopentixol (controls,n=100) were evaluated for extrapyramidal side effects (EPS) (blind) as well as other side effects and mental condition (non-blind). In both groups the patients had received neuroleptic treatment for a total of 14 years (median) and the present antipsychotic (clozapine or control drug) for 5 years. Thus the clozapine-treated patients had previously received traditional neuroleptics for 9 years (median). The study was both retrospective (0.3–19 years for clozapine, 0.3–24 years for control drug, by means of chart information) and prospective (1 year, with video-controlled evaluation of EPS). There was a significantly lower prevalence of tardive dyskinesia (TD) in clozapine treated patients than control patients, although prior to this treatment there were more TD patients in the clozapine group (P<0.05). This lower level of TD in the clozapine group was related to a lower induction of new cases (P<0.001) and a tendency towards greater disappearance of TD in the clozapine than in the control group (P=0.07). Clozapine treated patients without TD had started clozapine and ceased traditional neuroleptics at an earlier age than those with TD. Parkinsonian signs were seen in 33% of the clozapine patients versus 61% of the control patients, mainly as hypokinesia; tremor in 3% versus 11% and rigidity in 0 versus 19%. Psychic akathisia was found in 14% versus 40% and motor akathisia in 7% versus 29% of the patients, all differences significantly in favor of clozapine. Clozapine treated patients also had less neuroleptic-induced emotional indifference and depression, but more autonomic side effects than controls.     

Non-functional CYP2D6 alleles and risk for neuroleptic-induced movement disorders in schizophrenic patients

The use of classic anti-psychotic drugs in the long-term treatment of schizophrenia is associated with risk for extrapyramidal side-effects, such as akathisia, parkinsonism and tardive dyskinesia (TD). Approximately 5–10% of European Caucasians lack the cytochrome P450 enzyme CYP2D6 (so-called poor metabolizers; PM), which normally metabolizes several drugs including many neuroleptics. PM subjects may achieve high or toxic plasma levels upon standard drug therapy. In this study we have examined 100 subjects from the Nithsdale cohort of schizophrenic patients in South-west Scotland receiving long-term neuroleptic medication, which enabled us to perform both a cross-sectional and longitudinal evaluation of extrapyramidal side-effects in relation to the genetically impaired CYP2D6 metabolism. We identified ten (10%) schizophrenic subjects with the PM genotype. In the cross-sectional study, the prevalence of TD, parkinsonism and akathisia was 51%, 38% and 15%, respectively. Patients with TD or parkinsonism were significantly older than patients without these side-effects. In contrast, patients with akathisia were significantly younger than patients without akathisia. There was a non-significant tendency for PM subjects to have more severe ratings for TD and parkinsonism. In the long-term evaluation based on repeated ratings since 1981, there was a non-significant 3-fold higher frequency of PM subjects among schizophrenic patients with longitudinal TD, as compared with the group of patients with fluctuating or no TD. These results indicate that genetically impaired CYP2D6 metabolism may be a contributing factor for the development of persistent TD. Received: 16 October 1996 /Final version: 5 January 1997     

Liverpool University Neuroleptic Side-Effect Rating Scale (LUNSERS) as a subjective measure of drug-induced parkinsonism and akathisia

The Liverpool University Neuroleptic Side-Effect Rating Scale (LUNSERS) was examined for its usefulness as a subjective measure of drug-induced parkinsonism and akathisia. Eighty-three subjects were assessed using the LUNSERS, the Simpson-Angus Scale (SAS) and the Barnes Akathisia Rating Scale (BARS), before and after a 6-week treatment with olanzapine. Significant correlations were found between the changes in scores of parkinsonism items of LUNSERS and SAS. The changes in scores of akathisia item (restlessness), extrapyramidal side effects (EPS) subscale and psychic side-effects subscale of LUNSERS were significantly correlated with those of the BARS. 'Shakiness', one item of the EPS subscale of LUNSERS, correctly classified between parkinsonism and non-parkinsonism groups with 81.0% accuracy. A combination of four items included in EPS and psychic side-effect subscales of LUNSERS identified akathisia and non-akathisia groups with 76.2% accuracy. These results suggest that the EPS and psychic side-effect subscales of LUNSERS may be useful in screening for drug-induced parkinsonism and akathisia.     

Treatment predictors of extrapyramidal side effects in patients with tardive dyskinesia: results from Veterans Affairs Cooperative Study 394

Predictors for the development of tardive dyskinesia (TD) have been studied extensively over the years, yet there are few studies of predictors of the course of TD after it has developed. Moreover, few studies have examined predictors of the course of other extrapyramidal side effects (EPS) in patients maintained on neuroleptics. The purpose of this study was to determine which modifiable variables are important in the prediction of EPS in patients with persistent TD over a period of as long as 2 years. One hundred fifty-eight patients enrolled in the Veterans Affairs Cooperative Study 394 were included in this study. A linear mixed-effects (LME) analysis to estimate the Abnormal Involuntary Movement Scale score (for TD severity), Simpson-Angus Scale (for parkinsonism severity), and Barnes Akathisia Scale at any given time after intake assessment was performed. The severity of each of the TD and EPS outcomes at any given visit was predicted by their respective baseline severity scores. Additional predictors of a favorable course of TD included lower doses of antipsychotic medications and use of anticholinergic medications. Other predictors of a favorable course of EPS included younger age and the use of atypical antipsychotic medication (for rigidity) and the use of anticholinergic medication (for tremor). These findings indicate that clinician-modifiable factors related to medication usage can influence the outcome of TD and EPS in patients with persistent TD.     

Pharmacokinetic-pharmacodynamic analysis of antipsychotics-induced extrapyramidal symptoms based on receptor occupancy theory incorporating endogenous dopamine release

We aimed to analyze the risks of extrapyramidal symptoms (EPS) induced by typical and atypical antipsychotic drugs using a common pharmacokinetic-pharmacodynamic (PK-PD) model based on the receptor occupancy. We collected the data for EPS induced by atypical antipsychotics, risperidone, olanzapine and quetiapine, and a typical antipsychotic, haloperidol from literature and analyzed the following five indices of EPS, the ratio of patients obliged to take anticholinergic medication, the occurrence rates of plural extrapyramidal symptoms (more than one of tremor, dystonia, hypokinesia, akathisia, extrapyramidal syndrome, etc.), parkinsonism, akathisia, and extrapyramidal syndrome. We tested two models, i.e., a model incorporating endogenous dopamine release owing to 5-HT2A receptor inhibition and a model not considering the endogenous dopamine release, and used them to examine the relationship between the D2 receptor occupancy of endogenous dopamine and the extent of drug-induced EPS. The model incorporating endogenous dopamine release better described the relationship between the mean D2 receptor occupancy of endogenous dopamine and the extent of EPS than the other model, as assessed by the final sum of squares of residuals (final SS) and Akaike's Information Criteria (AIC). Furthermore, the former model could appropriately predict the risks of EPS induced by two other atypical antipsychotics, clozapine and ziprasidone, which were not incorporated into the model development. The developed model incorporating endogenous dopamine release owing to 5-HT2A receptor inhibition may be useful for the prediction of antipsychotics-induced EPS.     

Extrapyramidal side effects of clozapine and haloperidol

Neuroleptic-induced extrapyramidal side effects (EPS) were evaluated in 92 patients treated with clozapine for the first time and 59 patients treated with haloperidol followed in a drug monitoring program. Side effects were measured by the Columbia University Rating Scale, the Simpson Dyskinesia Scale and the Hillside Akathisia Scale. The cumulative incidence rate for tremor was found to be 24.4% in the clozapine group and 39.3% in the haloperidol group. This did not amount to a statistically significant group difference. Bradykinesia was observed in 21.8% of the patients treated with clozapine and in 47.7% of the patients of haloperidol (P=0.011). In the clozapine group the akathisia incidence rate was 5.6%, whereas haloperidol patients showed a higher rate of 31.7% (P=0.005). Our results show higher incidence rates of tremor and bradykinesia during clozapine treatment than previous studies. We conclude that clozapine is not entirely free of EPS, but they are usually less severe and of a different quality than side effects induced by typical antipsychotics.     

Incidence and correlates of acute extrapyramidal symptoms in first episode of schizophrenia.

The incidence and correlates of extrapyramidal symptoms (EPS) in neuroleptic treatment of schizophrenic patients have been reported for chronic patients but not for first-episode patients. We examined the incidence and correlates of extrapyramidal symptoms in a cohort of 70 treatment-naive patients who received fluphenazine at 20-40 mg/day for the first 10 weeks of treatment. Thirty-four percent of our sample developed parkinsonism, 18 percent developed akathisia, and 36 percent developed dystonia. Acute EPS were associated with greater baseline psychopathology. Acute EPS were also associated with better treatment outcome in terms of time to and level of remission. These findings suggest that the EPS response of neuroleptic-naive patients may differ from that of chronically ill patients and that acute EPS status may be an indicator of pharmacologic responsivity in this group.     

Extrapyramidal symptoms and residual psychopathology with low-dose neuroleptics

Residual psychopathology associated with EPS has been mainly assessed in experimental studies where neuroleptics were administered at standard, fixed dosages. The present study evaluates residual psychopathology in 69 schizophrenic patients treated with moderate, flexible doses of neuroleptics (430 mg eq. CPZ) at the out-patient Community Mental Health Services (CMHSs) in Bologna. Akathisia was present in 27.5 per cent of patients and parkinsonism in 27.5 per cent. A more severe psychopathological state was associated with both side-effects, as seen by significantly higher BPRS global scores. This severity was due to tension and anxiety-depression symptoms in patients with akathisia and to negative symptomatology in patients with parkinsonism, as shown by significant associations with BPRS subscales ANS-DEP and NEG, respectively. In conclusion, the present study underlines that EPS are frequent even in an out-patient setting where moderate neuroleptic doses are employed, and more importantly shows that in these conditions, the residual psychopathology resulting from EPS is clinically very significant. Copyright 2000 John Wiley & Sons, Ltd.     

Cocaine is a major risk factor for antipsychotic induced akathisia, parkinsonism and dyskinesia

Objective: To assess the relative contribution of different drugs of abuse to extrapyramidal side effects (EPS) of antipsychotic drugs. Method: 106 consecutively contacted or admitted male patients in the Psychiatric Center of Surinam (PCS) with schizophrenia or a related disorder were included. Prevalence and severity of EPS were measured with the Unified Parkinson's Disease Rating Scale (UPDRS), the Abnormal Involuntary Movement rating Scale (AIMS), the Barnes Akathisia Rating Scale (BARS) and the Dystonia rating scale. Recent use of cigarettes, cannabis, alcohol, and cocaine were assessed. Standard multiple regression analyses were used to evaluate the relative contribution of above-mentioned drugs of abuse controlled for milligrams haloperidol equivalent a day and use of anticholinergic medication. Results: Recent cocaine use was significantly associated with severity of dyskinesia (p = 0.001), parkinsonism (p = 0.007), and akathisia (p < 0.001) (n = 106). Conclusions: Recent cocaine use is a major risk factor for antipsychotic induced EPS.     

Reduction in neuroleptic-induced movement disorders after a switch to quetiapine in patients with schizophrenia

BACKGROUND: Persistent neuroleptic-induced movement disorders limit effective pharmacological management of psychotic disorders. Although antipsychotic switching is a common strategy for managing extrapyramidal side effects (EPSs), there is insufficient empirical support to guide the clinician. We designed the present study to examine whether patients with preexisting EPS switched to quetiapine would show greater reduction in EPS compared with control patients. METHODS: Twenty-two patients with schizophrenia meeting clinical criteria for tardive dyskinesia or coexisting parkinsonism were randomized either to switch from their current antipsychotic to quetiapine (n = 13) or to remain on their current treatment (n = 9). A battery of standard clinical assessments for EPS along with electromechanical instrumental measures was administered before randomization and again 1 and 3 months postrandomization. RESULTS: We observed significant reduction in parkinsonism (P < 0.001) and akathisia (P = 0.02) based on clinical assessments and dyskinesia (P < 0.05) based on instrumental assessment for the quetiapine group. Subjects remaining on current treatment exhibited an increase in rigidity (P < 0.05) based on instrumental measures. CONCLUSIONS: These findings support the switching to quetiapine in the management of preexisting neuroleptic-induced extrapyramidal side effects.     

A comparison of extrapyramidal symptoms in older outpatients treated with quetiapine or risperidone

OBJECTIVE: To compare the tolerability of quetiapine with risperidone in older outpatients. RESEARCH DESIGN AND METHODS: Post hoc analysis of a subset of older patients (aged 60-80; n = 92) from a randomized, 4-month, multicenter, open-label trial comparing quetiapine and risperidone in an outpatient setting. Participants had various neuropsychiatric disorders associated with psychosis as defined by criteria from the Diagnostic and Statistical Manual of Mental Disorders (4th edn). MAIN OUTCOME MEASURES: The main outcome measure was an extrapyramidal symptoms (EPS) checklist, used to assess motor symptoms, including parkinsonism, at baseline and after treatment. The Positive and Negative Syndrome Scale (PANSS) and the Clinical Global Impression scale were used to assess therapeutic efficacy. RESULTS: Substantial EPS (defined as EPS requiring a dosage adjustment or use of medication to reduce EPS) occurred less often with quetiapine (median dosage, 200 mg/day) than with risperidone (median dosage, 3 mg/day); odds ratio, 0.31 (P < 0.03). Quetiapine was also less likely than risperidone to cause akathisia or hypertonia. Both compounds produced comparable reductions in PANSS scores. CONCLUSIONS: Interpretation of findings in this report is limited by the open-label design of the study and the post hoc nature of this analysis. However, the results suggest that quetiapine, when given within the recommended dosage range, has a benign EPS profile, with potentially greater tolerability and comparable efficacy to risperidone in older outpatients with psychotic disorders.     

Risperidone in the treatment of tourette syndrome: a double-blind, placebo-controlled trial.

A double-blind, placebo-controlled trial was performed to determine the efficacy and tolerability of 8 weeks of treatment with risperidone in the management of 48 adolescent and adult patients with Tourette syndrome. Twenty-four patients were randomly assigned to treatment with risperidone in doses of 0.5 to 6.0 mg/day, and 24 were assigned to placebo. The dosage of medication was increased in fixed increments during the first week of double-blind treatment and thereafter in a flexible dose regimen according to clinical response. Risperidone, at a median dose of 2.5 mg/day (range, 1 to 6 mg/day), was found to be significantly ( p < 0.05) superior to placebo on the Global Severity Rating of the Tourette Syndrome Severity Scale. The proportion of patients who improved by at least one point on this seven-point scale was 60.8% in the risperidone group and 26.1% in the placebo group. Treatment with risperidone was accompanied by an improvement in global functioning in patients with average to above-average impairment at baseline as measured by the Global Assessment of Functioning scale. With respect to extrapyramidal symptom scores measured on the Extrapyramidal Symptom Rating Scale, hypokinesia and tremor increased in the risperidone group, but the effect on tremor was largely confined to subjects with higher baseline tremor scores. There were no significant differences in dystonic reactions, dyskinetic movements, subjective parkinsonism, or akathisia. Risperidone did not increase obsessive-compulsive symptoms. Fatigue and somnolence were the most common adverse events associated with risperidone.     

Diminished neurocardiac dynamics associated with antipsychotic-induced extrapyramidal syndrome.

The relationship between antipsychotic-induced extrapyramidal syndrome (EPS) and the autonomic neurocardiac function was examined in 57 schizophrenic patients treated with atypical antipsychotics. Comprehensive assessments of EPS and heart rate dynamics were performed. There was a significant negative correlation of non-hypokinetic parkinsonism, akathisia, and dyskinesia with several linear and novel non-linear heart rate dynamics measures, suggesting reduced neurocardiac dynamics associated with some forms of EPS. Assessment of heart rate dynamics may be useful for the detection of these adverse effects and may serve as a useful non-invasive method providing a dynamic window into the alterations of complex neuronal activity.     

Extrapyramidal symptoms with atypical antipsychotics : incidence, prevention and management.

The treatment of schizophrenia changed drastically with the discovery of antipsychotic medications in the 1950s, the release of clozapine in the US in 1989 and the subsequent development of the atypical or novel antipsychotics. These newer medications differ from their conventional counterparts, primarily based on their reduced risk of extrapyramidal symptoms (EPS). EPS can be categorised as acute (dystonia, akathisia and parkinsonism) and tardive (tardive dyskinesia and tardive dystonia) syndromes. They are thought to have a significant impact on subjective tolerability and adherence with antipsychotic therapy in addition to impacting function. Unlike conventional antipsychotic medications, atypical antipsychotics have a significantly diminished risk of inducing acute EPS at recommended dose ranges. These drugs may also have a reduced risk of causing tardive dyskinesia and in some cases may have the ability to suppress pre-existing tardive dyskinesia. This paper reviews the available evidence regarding the incidence of acute EPS and tardive syndromes with atypical antipsychotic therapy. Estimates of incidence are subject to several confounds, including differing methods for detection and diagnosis of EPS, pretreatment effects and issues surrounding the administration of antipsychotic medications. The treatment of acute EPS and tardive dyskinesia now includes atypical antipsychotic therapy itself, although other adjunctive strategies such as antioxidants have also shown promise in preliminary trials. The use of atypical antipsychotics as first line therapy for the treatment of schizophrenia is based largely on their reduced risk of EPS compared with conventional antipsychotics. Nevertheless, EPS with these drugs can occur, particularly when prescribed at high doses. The EPS advantages offered by the atypical antipsychotics must be balanced against other important adverse effects, such as weight gain and diabetes mellitus, now known to be associated with these drugs.     

Risk factors for orofacial and limbtruncal tardive dyskinesia in older patients: a prospective longitudinal study

Although there is a consensus that orofacial and limbtruncal subtypes of tardive dyskinesia (TD) exist and may represent distinct pathophysiologic entities, few studies have examined the incidence of and risk factors associated with the development of these TD subtypes. Two hundred and sixty-six middle-aged and elderly outpatients with a median duration of 21 days of total lifetime neuroleptic exposure at study entry were evaluated at 1- to 3-month intervals. Using mild dyskinesia in any part of the body for diagnosis of TD, the cumulative incidence of orofacial TD was 38.5 and 65.7% after 1 and 2 years, respectively, whereas that of limbtruncal TD was 18.6 and 32.6% after 1 and 2 years. Preclinical dyskinesia was predictive of both orofacial and limbtruncal TD. History of alcohol abuse or dependence was a significant predictor of orofacial TD only whereas tremor was a significant predictor of limbtruncal TD only. Findings support suggestions that orofacial and limbtruncal TD may represent specific subsyndromes with different risk factors.     

Antipsychotic-Induced movement disorders in the elderly: epidemiology and treatment recommendations

We reviewed the epidemiological aspects of antipsychotic-induced movement disorders as they pertain to older patients. The incidence and prevalence of drug-induced parkinsonism and tardive dyskinesia (TD) are significantly greater in the older patient than in the younger patient whereas akathisia seems to occur evenly across the age spectrum and dystonia is uncommon among older patients. The literature on risk factors associated with treatment-emergent movement disorders is highly variable. Treatment practices vary across the age range and the interaction between age and antipsychotic dosage confounds our understanding of the relative importance of treatment-related risk factors. However, there is general agreement that pre-existing extrapyramidal signs (EPS) increase the vulnerability of the patient to developing significant drug-induced movement disorders. Elderly patients with dementia are at greater risk than patients without dementia for persistent drug-induced EPS. Management of drug-induced movement disorders in the older patient requires careful consideration of the contraindications imposed by such agents as anticholinergics and beta-blockers. At present, well-controlled double-blind studies of second-generation antipsychotics such as clozapine, risperidone. olanzapine or quetiapine for reducing the risk of treatment-emergent movement disorders in the elderly have not been published. However, open-label studies of atypical antipsychotics demonstrate a markedly lower incidence of both EPS and TD compared with conventional antipsychotic treatment in the elderly. There is emerging literature in support of atypical antipsychotics for the treatment of existing drug-induced movement disorders. More controversial is the use of adjunctive antioxidants in newly treated patients who are vulnerable to drug-induced movement disorders. While the evidence is mixed in support of antioxidants for the treatment of TD, the possibility remains that prophylactic use of antioxidants may help reduce the incidence of TD. The development of a drug-induced movement disorder often reduces the quality of life in an elderly patient. Effective pharmacological management requires cooperation from the patient and family, which can be fostered early in the patient's care through proper informed consent. The risks and benefits of antipsychotic treatment in the elderly patient need to be communicated to the patient and family. At the present time, there is no consistently effective treatment for patients with TD once it develops. Therefore, attention should focus on its prevention and close monitoring.     

A randomised controlled study of risperidone and olanzapine for schizophrenic patients with neuroleptic-induced acute dystonia or parkinsonism

The objective of this study was to compare the effects of risperidone and olanzapine in schizophrenic patients with intolerant extrapyramidal side effects (EPS) on first generation antipsychotics. We conducted an 8-week, rater-blinded, flexible dose study. Seventy patients with schizophrenia, who met the DSM-IV research criteria of having neuroleptic-induced acute dystonia or parkinsonism, were randomly assigned to risperidone or olanzapine group. The primary outcome was a comparison of the incidence of concomitant anticholinergic drugs usage between the groups to manage their acute dystonia and parkinsonism. The average doses of risperidone and olanzapine from baseline to study end point were 1.8-3.5 mg/day and 7.7-11.7 mg/day, respectively. There were no significant differences in demographic data, severity of EPS or psychotic symptoms between the groups at baseline assessment. Patients taking risperidone had significantly higher incidence of using anticholinergic drugs to manage acute dystonia or parkinsonism overall during the study (OR = 5.17, 95%CI = 1.49-17.88, P = 0.013). There was no significant between-group difference in the changing of rating scales of EPS and psychotic symptoms. The results of our study favour olanzapine as a better choice in schizophrenic patients with intolerant EPS. Double-blinded, fixed dose and different ethnical study for EPS-intolerant schizophrenic patients is needed to confirm the results of our study.     

Extrapyramidal symptom profiles assessed with the Drug-Induced Extrapyramidal Symptom Scale: comparison with Western scales in the clinical double-blind studies of schizophrenic patients treated with either olanzapine or haloperidol

The superiority of olanzapine to haloperidol with respect to a decreased incidence of treatment-emergent extrapyramidal syndromes (EPS) in patients with schizophrenia was demonstrated in studies conducted in both Japan and Western countries. EPS measurements used in Western countries included the Simpson-Angus, Barnes akathisia and the Abnormal Involuntary Movement Scale, while the Drug-Induced Extrapyramidal Symptom Scale (DIEPSS) was used in Japan. The aim of this study was to clarify how the DIEPSS captures EPS profiles. The baseline prevalence and treatment-emergent incidence of EPS in Japanese schizophrenic patients treated with olanzapine or haloperidol were retrospectively compared as assessed by the DIEPSS to the prevalence and incidence of EPS in primarily Caucasian schizophrenic patients who were treated with olanzapine or haloperidol. Specifically, the prevalence and incidence of dyskinesia, akathisia and parkinsonism were compared between the Japanese trial and an international trial to examine if appropriate definitions using the DIEPSS can be derived assuming that a comparable prevalence and incidence of the syndromes would be observed when any differences in residual antipsychotic exposure at the initiation of study treatment were accounted for. For the incidence of all EPS syndromes, odds ratios were observed to be similar between the two studies, indicating that appropriate criteria for the clinical diagnosis of the EPS syndromes could be established based on the DIEPSS. This preliminary and retrospective work suggests that the DIEPSS can be used to operationally define the presence or absence, and make the clinical diagnosis, of specific EPS syndromes.