Published papers

OBJECTIVE: In younger patients with schizophrenia, positron emission tomography (PET) studies have identified a therapeutic window of striatal dopamine D2/3 receptor occupancy of 65%-80%. This type of empirical information is not available in late life. Our primary aim was to assess the effect of changes in D2/3 relative receptor occupancy (RRO) on clinical outcomes in this population. DESIGN: Open-label intervention. SETTING: Centre for Addiction and Mental Health, Toronto. PARTICIPANTS: Subjects with schizophrenia age 50 years or more who were clinically stable and previously maintained on oral risperidone for more than 6 months. INTERVENTION: A dose reduction of risperidone of up to 40%, followed by a 3-month follow-up. MEASUREMENTS: Dopamine D2/3 RRO in dorsal putamen was assessed, using the region of interest analysis of [C]raclopride PET scans, before and after the dose reduction. Clinical assessments included the Positive and Negative Syndrome Scale and the Simpson-Angus Scale. RESULTS: Nine subjects (mean ± SD age: 58 ± 7 years; mean ± SD baseline risperidone dose: 3.4 ± 1.6 mg/day) participated in the study. Extrapyramidal symptoms (EPS) were present in six subjects and were associated with 70% or more D2/3 RRO in the putamen (range: 70%-87%). Following the dose reduction, EPS resolved in five subjects. Two subjects experienced a clinical worsening at 52% and at less than 50% D2/3 RRO. CONCLUSION: EPS diminished less than 70% D2/3 RRO, which suggests a lower therapeutic window for older patients with schizophrenia than that for younger patients. Although these findings have to be replicated in a larger sample, they have important implications for future drug development and clinical guidelines in late-life schizophrenia.

Objective: While 65%-80% occupancy of dopamine D 2 receptors with antipsychotics has been proposed to achieve optimal therapeutic response during acute treatment of schizophrenia, it remains unclear as to whether it is also necessary to maintain D 2 receptor occupancy within this "safe" window for ongoing maintenance treatment. The data are especially scarce for long-acting antipsychotic formulations. Method: Clinically stable patients with schizophrenia (DSM-IV) receiving a stable dose of risperidone long-acting injectable (LAI) as antipsychotic monotherapy for at least 3 months and free of any psychiatric hospitalization over the past 6 months were included. Dopamine D 2 receptor occupancy levels at trough were estimated from plasma concentrations of risperidone plus 9-hydroxyrisperidone immediately before the intramuscular injection of risperidone LAI, using a 1-site binding model derived from our previous positron emission tomography data. This study was conducted from October to December 2011. Results: 36 patients were included in this study (mean ± SD age, 49.3 ± 14.0 years; mean ± SD dose and interval of injections, 38.2 ± 11.6 mg and 16.5 ± 14.0 days, respectively). Mean ± SD D 2 receptor occupancy was 62.1% ± 15.4%; 52.8% of the subjects (n = 19) did not demonstrate an occupancy of ≥ 65%. On the other hand, 13.9% (n = 5) showed a D 2 occupancy as high as over 80% at the estimated trough. Conclusions: More than half of patients taking risperidone LAI maintained clinical stability without achieving continuous blockade of dopamine D 2 receptors ≥ 65% in real-world clinical settings. Results suggest that sustained dopamine D 2 receptor occupancy levels of ? 65% may not be necessary for maintenance treatment with risperidone LAI in schizophrenia.

Background: Clinical relevance of dental caries is often underestimated in patients with schizophrenia. The objective of this study was to examine dental caries and to identify clinical and demographic variables associated with poor dental condition in patients with schizophrenia.Methods: Inpatients with schizophrenia received a visual oral examination of their dental caries, using the decayed-missing-filled teeth (DMFT) index. This study was conducted in multiple sites in Japan, between October and December, 2010. A univariate general linear model was used to examine the effects of the following variables on the DMFT score: age, sex, smoking status, daily intake of sweets, dry mouth, frequency of daily tooth brushing, tremor, the Clinical Global Impression-Schizophrenia Overall severity score, and the Cumulative Illness Rating Scale for Geriatrics score.Results: 523 patients were included in this study (mean ± SD age = 55.6 ± 13.4 years; 297 men). A univariate general linear model showed significant effects of age group, smoking, frequency of daily tooth brushing, and tremor (all p's < 0.001) on the DMFT score (Corrected Model: F (23, 483) = 3.55, p < 0.001, R 2 = 0.42) . In other words, older age, smoking, tremor burden, and less frequent tooth brushing were associated with a greater DMFT score.Conclusions: Given that poor dental condition has been related with an increased risk of physical co-morbidities, physicians should be aware of patients' dental status, especially for aged smoking patients with schizophrenia. Furthermore, for schizophrenia patients who do not regularly brush their teeth or who exhibit tremor, it may be advisable for caregivers to encourage and help them to perform tooth brushing more frequently.

Treatment-resistant schizophrenia (TRS) has been defined mainly by severity of (positive) symptoms and response to antipsychotics derived from a relative change in the representative scales (most frequently ≥. 20% decrease in the Positive and Negative Syndrome Scale: PANSS), but these definitions have not necessarily been consistent. Integrating past evidence and real-world practicability, we propose that TRS be defined by at least two failed adequate trials with different antipsychotics (at chlorpromazine-equivalent doses of ≥. 600. mg/day for ≥. 6 consecutive weeks) that could be retrospective or preferably include prospective failure to respond to one or more antipsychotic trials. In addition, our proposed criteria require both a score of ≥. 4 on the Clinical Global Impression (CGI)-Severity and a score of ≤. 49 on the Functional Assessment for Comprehensive Treatment of Schizophrenia (FACT-Sz) or ≤. 50 on the Global Assessment of Functioning (GAF) scales to define TRS. Once TRS is established, we propose that subsequent treatment response be defined based on a CGI-Change score of ≤. 2, a ≥. 20% decrease on the total PANSS or Brief Psychiatric Rating Scale (BPRS) scores, and an increase of ≥. 20 points on the FACT-Sz or GAF. While these suggestions provide a pragmatic framework for TRS classification, they need to be tested in future trials.

Background: Due to high interindividual variability in peripheral pharmacokinetic parameters, dosing of antipsychotics relies on clinical trial and error. This blind process of upward or downward clinical dose titration carries a risk of relapse and adverse effects in the treatment of schizophrenia. Using population pharmacokinetic methods, the authors therefore sought to predict plasma concentrations of risperidone (RIS) plus 9-hydroxyrisperidone (9-OH-RIS) before a dosage change. Methods: Two plasma samples were collected at 2 separate given time points for the measurement of RIS and 9-OH-RIS concentrations from 50 patients with schizophrenia or schizoaffective disorder maintained on risperidone (mean ± SD age = 56 ± 15 years; 39 men). After an oral risperidone dose adjustment, a third sample was collected. The plasma concentration of the third sample was individually predicted in a blinded fashion with the 2 baseline plasma concentrations before dose adjustment and clinical and demographic information, using the mixed-effects model with NONMEM that was derived from the data of the Clinical Antipsychotic Trials in Intervention Effectiveness study. Results: The mean (95% confidence interval) prediction errors (in ng/mL) were as low as 0.0 (-1.3 to 1.4) for RIS and 1.0 (-1.1 to 3.0) for 9-OH-RIS. The observed and predicted concentrations of RIS and 9-OH-RIS were highly correlated (r = 0.96, P < 0.0001 and r = 0.92, P < 0.0001, respectively). Conclusions: Antipsychotic plasma concentrations can be predicted before risperidone dose adjustment. In light of the known relationship between plasma drug concentration, dopamine D2 receptor occupancy, and clinical effects, our results confirm that individualized dosing with the measurement of antipsychotic plasma concentrations has the potential for bedside clinical application.

In treating schizophrenia, it has been established that 65-80% occupancy of dopamine D2 receptors optimizes therapeutic efficacy while minimizing risks of extrapyramidal symptoms. However, it is unclear as to whether it is necessary to keep D2 receptor occupancy within this therapeutic window to maintain response. In this study, daily peak and trough D2 receptor occupancy levels were estimated in clinically stable patients with schizophrenia (DSM-IV) who were receiving risperidone or olanzapine. Using two collected plasma samples, plasma antipsychotic concentrations at peak and trough were estimated with population pharmacokinetic techniques. Corresponding dopamine D2 receptor occupancy levels were then estimated, using a recently developed model. 35 subjects with stable schizophrenia completed the study (mean ± SD age, 48.8 ± 13.8. years; male [N = 14]; Asians [N = 23], Caucasians [N = 12]; risperidone [N = 20] at 3.2 ± 2.3. mg/day, and olanzapine [N = 15] at 9.2 ± 4.9. mg/day) between September and December 2010. 48.6% (N = 17) did not achieve a continuous blockade of ≥ 65%. Moreover, 11.4% (N = 4) did not achieve the 65% threshold at estimated peak concentrations. In conclusion, approximately half the subjects with stable schizophrenia did not achieve estimated continuous blockade of D2 receptor occupancy of ≥ 65%. The results suggest that sustained D2 receptor occupancy levels of ≥ 65% may not always be necessary for the maintenance treatment of schizophrenia.

Once developed, tardive dyskinesia (TD) is a challenging condition to treat. The recent evidence has indicated that zonisamide, an antiepileptic drug indicated for partial-onset seizures, may also have beneficial effects for ameliorating dyskinesia in Parkinson's disease. However, this finding has not systematically been tested in psychiatric patients with TD associated with antipsychotic treatment. The objective of this study was to examine the efficacy, tolerability, and safety of zonisamide against TD in these patients. In this 4-week open-label study, subjects who suffered TD were given 50-100 mg/day of add-on zonisamide. Severity of TD was evaluated at the baseline and endpoint, using the Abnormal Involuntary Movement Scale (AIMS). Eleven subjects (6 females; mean ± SD age, 75.5 ± 4.7 years; schizophrenia [N = 6], bipolar affective disorder [N = 2], schizoaffective disorder [N = 1], mental retardation [N = 1], mental retardation with epilepsy [N = 1]; 6 were antipsychotic free at baseline) participated in this study. The AIMS total score (mean ± SD) was significantly decreased from 24.1 ± 5.5 to 19.5 ± 5.9, with 36.4% of the subjects (N = 4) demonstrating 20% or more decrease in the AIMS total score. Treatment with zonisamide was well-tolerated and no participants dropped out prematurely. In conclusion, zonisamide may be safe and effective for the treatment of TD associated with antipsychotic treatment. These preliminary findings need to be further explored by larger well-designed trials.

Objective: Antipsychotic treatment strategy for the maintenance phase of schizophrenia has been inconsistent in the literature. The purpose of this systematic review is to overview recommendations in various guidelines and algorithms. Methods: The guidelines and algorithms for schizophrenia that were published or updated in English after 2000 were searched, using Medline, PubMed, EMBASE, and PsycINFO with the following key words: guideline, algorithm, schizophrenia, and psychosis (last search: July 2011). The reference lists of the relevant reports were also examined. Results: Fourteen guidelines and algorithms were identified; only five of them clearly defined terms about the maintenance phase and treatment. Ten of 11 guidelines and algorithms did not recommend discontinuation of antipsychotics within five years; six of them partially recommended antipsychotic discontinuation for patients with first-episode schizophrenia exclusive. All nine guidelines and algorithms that referred to intermittent or targeted antipsychotic strategy endorsed against this strategy. Although being a hot topic of controversy, dose reduction of antipsychotics or lower dose therapy in the maintenance phase compared to the acute dosage is not recommended on the whole concerning atypical antipsychotics, whereas dose reduction appears sometimes considered acceptable for typical antipsychotics. Conclusion: What constitutes maintenance phase and its treatment in schizophrenia has not yet been established in the literature. While discontinuation and intermittent or targeted strategies are not generally recommended, there is controversy regarding dose reduction or lower dose therapy, especially with regards to atypical antipsychotics. Further evidence is needed in order to derive treatment recommendations on antipsychotics in this critical treatment phase of schizophrenia.

Although patients with schizophrenia are reported to have excess mortality compared with the general population, many affected patients will nonetheless survive and continue to have the disorder in later life. Consequently, geriatric schizophrenia will be a significant public health concern in the years to come, and evidence-based treatment of schizophrenia in older patients is becoming an urgent issue. However, there has been a paucity of comparative data to guide selection of antipsychotics for schizophrenia in late life.The primary aim of this review was to synthesize the available evidence on management of late-life schizophrenia with antipsychotic medications; a secondary aim was to evaluate treatment resistance in this population. Accordingly, PubMed and EMBASE were searched using the keywords 'antipsychotics', 'age' and 'schizophrenia' to identify psychopharmacological studies of antipsychotics in late-life schizophrenia (last search 30 April 2011). The literature search identified 23 prospective studies of use of antipsychotics for schizophrenia in older patients (generally age ≥65 years), including eight double-blind trials. The sample size was smaller than 40 patients for 52 of the studies. Two of the double-blind studies were post hoc analyses and one was a placebo-controlled trial. In the largest double-blind study, olanzapine (n88, median dose 10mgday) and risperidone (n87, median dose 2mgday) were compared in patients not resistant to these therapies, with similar effects. There have also been several open-label trials of these two agents that have shown efficacy and tolerability in non-resistant patients. Evidence on other antipsychotics has been scarce and less robust.The gold standard for treatment-resistant schizophrenia is clozapine. However, almost all of the studies of clozapine to date have effectively excluded older patients with schizophrenia. Only one small study has evaluated clozapine (n24, mean dose 300mgday) in comparison with chlorpromazine (n18, mean dose 600mgday) in a difficult-to-treat older population; the investigators reported that both treatments were similarly efficacious. Furthermore, there has been little compelling evidence in favour of or against augmentation of antipsychotics with other psychotropic medications in the older age group.Treatment of non-resistant, late-life schizophrenia with olanzapine and risperidone appears to be supported by the available evidence. However, data on geriatric patients with schizophrenia are generally scarce, particularly for treatment-resistant subpopulations, underscoring the need for more research in this important area.

Background: Clozapine has been serving as the gold standard medication for patients with treatment-resistant schizophrenia who failed to respond to other antipsychotics. However, factors affecting response to this medication have not been comprehensively reviewed recently. Methods: In order to find factors associated with response to clozapine in schizophrenia, a literature search was conducted using PubMed through January 2011 with keywords of clozapine, response, and schizophrenia. Cross-referencing of relevant articles was also performed. Factors were arbitrarily classified into the following: demographic/clinical, oral dosage/pharmacokinetic, biochemical, (electro)physiological, genetic, imaging, and combinations. Results: A synthesis from 280 articles indicated that demographic and clinical variables such as high baseline symptoms and low premorbid functioning have not been particularly useful in predicting response to clozapine. Pharmacokinetic evidence points to a threshold clozapine level of 350 ng/ml but in a context of significant inter- as well as intra-individual variability. Pharmacokinetic perspectives appear to have more implication in special situations including poor response, suspected toxicity and nonadherence. A number of laboratory-based studies have reported on many potential candidates for response prediction to clozapine, however, reproducibility, specificity, robustness of the findings, as well as clinical feasibility and cost-effectiveness all pose a significant practical challenge, in relation with the fact that pathophysiological bases of treatment resistance in schizophrenia largely remain to be elucidated. Conclusions: No unequivocal factors to clozapine response were found despite a relatively rich body of the literature, which calls for more works on this important topic. Clozapine level of 350 ng/ml appears to be useful in case of nonresponse.

Background: There remains a lack of agreement regarding criteria for treatment-resistant schizophrenia (TRS) and definition of response. Method: A literature search was conducted to identify clinical studies of antipsychotics in TRS using PubMed, EMBASE and PsycINFO (last search 31 July 2011). Psychopharmacological studies with the number of participants of ≥ 40 were evaluated in terms of definitions for TRS and subsequent treatment response. Results: Thirty-three studies of antipsychotics in TRS were reviewed. TRS has been defined mainly by severity in symptoms. Many studies based TRS with at least 2 failed adequate antipsychotic trials (at chlorpromazine equivalent doses of ≥ 1000. mg/day for ≥ 6. weeks), but some studies adopted prospective treatment arm to be certain of sample refractoriness. Treatment response has been defined by a relative change in the representative scales (most commonly ≥ 20% decrease in the Positive and Negative Syndrome Scale), but it sometimes included the absolute criteria such as post-treatment score of ≤ 35 in the Brief Psychiatric Rating Scale or Clinical Global Impression-severity score of ≤ 3 (mild or less severe). Social functioning has not been a primary outcome measure in past pivotal trials, and other important domains of the illness such as cognition and subjective perspectives have not been incorporated into definitions of treatment resistance or response. However, adopting various assessment scales can be time-consuming and complicated, with an additional possibility of disagreement among raters. Conclusion: Defining outcomes in schizophrenia is a challenging task. It is imperative that the field agrees on how this population is better defined and what constitutes treatment response.

Background: While it has been reported that physicians may under-recognize adverse effects of antidepressants thoroughly in clinical settings, subjective bias in recognition of adverse effects (AEs) with antidepressants has not been specifically investigated. Methods: Four-hundred ninety-three participants with depressive disorders (ICD-10) were assessed for the severity of 20 common AEs and their inferred causal relationship with antidepressants, together with the Quick Inventory for Depressive Symptoms (QIDS). These assessments occurred twice at the 1st visit (when they were antidepressant free) and 2nd visit (10 days after the initiation of antidepressants). 'Possible AEs' and 'under-recognized AEs' were defined as 'events with exacerbation in the severity' and 'events with negative causal attribution to antidepressants' at the time of the 2nd visit, respectively. Results: Three-hundred sixty-three participants (73.6%) experienced ≥1 under-recognized AEs. Flu like symptoms (96.5% of participants who experienced possible AEs), sexual dysfunction (94.2%), blurred vision (93.4%), anxiety/tension (91.1%) and sweating (89.2%) were found to be prevalent as under-recognized AEs. Participants with under-recognized AEs had less improvement in the QIDS than those without (27.1% vs. 11.1% decrease, p < 0.001). Limitations: It is intrinsically challenging to exactly differentiate between antidepressant AEs and symptoms of depression. And the severity of depression, that of AEs and causal relationship between AEs and antidepressants were assessed not by objective but subjective scales. Conclusions: An overall trend to under-recognize AEs of antidepressants was found and people with a lesser degree of early improvement tend to understate the causality, which has an implication in interpreting voluntarily expression of AEs.

Investigating and characterizing the degree and correlates of patient's trust in their treating psychiatrists across a range of psychiatric disorders is of a great clinical relevance to enhance our therapeutic alliance, which has not been addressed in the literature. In this study, outpatients who visited one of the participating psychiatric clinics in Tokyo, Japan between October and November, 2010 were asked to complete the Trust in Physician Scale (TPS), an 11-item self-report questionnaire. A univariate general linear model was used to examine the effects of the following variables on the TPS total score: age, sex, diagnosis, Global Assessment of Functioning score, educational background, physician's years of practice as a psychiatrist, duration of treatment with their current psychiatrists, sex concordance between patients and their psychiatrists, and whether patients were older than their psychiatrists. Five hundred and four patients were enrolled (mean ± SD age = 42.8 ± 13.6 years; 176 men; Psychiatric diagnoses (ICD-10): F0 [N = 8], F2 [N = 72], F3 [N = 252], F4 [N = 147], F6 [N = 22]). A duration of treatment with their current psychiatrist of ≥1 year and a duration of their physician's clinical expertise as a psychiatrist for ≥10 years were associated with a greater degree of patient's trust in their psychiatrist. Furthermore, patients with a F3 diagnosis showed a significantly higher TPS total score than those with F4. These findings underscore an importance of paying close attention to patients who are relatively new and are not treated by well-experienced psychiatrists in terms of subjective trust. Furthermore, this likely holds more true for patients with neurotic disorders.

Objective We explored whether prior findings of reduction in serotonin 2A receptor (5-HT 2AR) binding with age could be replicated and whether high resolution research tomography (HRRT) for positron emission tomography could compensate for partial volume effects in the presence of age-related brain atrophy, which has been a traditional concern for radioligand PET studies in the elderly. Methods We derived 5-HT 2AR nondisplaceable binding potentials (BP ND) in frontal, temporal, anterior-cingulate, insula, caudate and putamen volumes of interest (VOIs) for 28 healthy subjects (mean ± SD age = 43.9 ± 17.0 years, range: 19-78 years) using HRRT. Partial volume correction (PVC) was performed in the VOI analysis. Results The 5-HT 2AR BP NDs decreased with age, a relationship best described by an exponential-decay regression. The BP NDs were found to be consistent before and after PVC, with an intra-class correlation coefficient of 0.84 and 95% confidence interval = 0.78-0.88. Conclusions These new findings update current knowledge, in that the aging process is not always uniform across the life span and suggest that PVC may not be necessary with HRRT in healthy subjects.

Rationale: Treatment guidelines for major depressive disorder (MDD) recommend a continuous use of antidepressants for several weeks, while recent meta-analyses indicate that antidepressant efficacy starts to appear within 2. weeks and early treatment nonresponse is a predictor of subsequent nonresponse. Objectives: We prospectively compared 8-week outcomes between switching antidepressants and maintaining the same antidepressant in early nonresponders, to generate a hypothesis on possible benefits of early switching strategy. Method: Patients with MDD without any treatment history for the current episode were included. When subjects failed to show an early response (i.e., ≥ 20% improvement in the Montgomery-Åsberg Depression Rating Scale (MADRS)) to the initial treatment with sertraline 50. mg at week 2, they were randomly divided into two groups; in the Continuing group, sertraline was titrated at 50-100. mg, whereas sertraline was switched to paroxetine 20-40. mg in the Switching group. A primary outcome measure was a response rate (i.e., ≥ 50% improvement in the MADRS) at week 8. Results: Among 132 subjects, 41 subjects showed early nonresponse. The Switching group (n = 20) showed a higher rate of responders than the Continuing group (n = 21) (75% vs. 19%: p = 0.002). Further, the Switching group was also superior in the rate of remitters (total score of ≤ 10 in the MADRS) (60% vs. 14%: p = 0.004) and continuous changes in the MADRS (19.0 vs. 7.5: p < 0.001). Conclusions: Our preliminary findings suggest that patients with MDD who fail to show early response to an initial antidepressant may derive benefits from the early switching antidepressants in the acute-phase treatment of depression.

Objective: The objective of this study was to evaluate the relationship between antipsychotic-induced tardive dyskinesia (TD) and estimated dopamine D2 receptor occupancy levels in patients with schizophrenia, using the dataset from the Clinical Antipsychotic Trials in Intervention Effectiveness (CATIE). Methods: The dataset from 218 subjects (risperidone, N = 78; olanzapine, N = 100; ziprasidone, N = 40) who presented with a score of zero on the Abnormal Involuntary Movement Scale (AIMS) at baseline in Phase 1 of the CATIE study, and remained for ≥. 6. months, was used. Peak and trough dopamine D2 receptor occupancy levels on the day of the AIMS assessment at the endpoint were estimated from plasma antipsychotic concentrations, using population pharmacokinetic analysis and our D2 prediction model. The estimated dopamine D2 receptor occupancy levels were compared between patients who presented an AIMS score of ≥. 2 at endpoint and those with a score of zero, using the Mann-Whitney U test. Results: Estimated dopamine D2 receptor occupancy levels at trough were significantly higher in subjects who developed involuntary movements (N = 23) than those who did not (N = 195) (71.7. ±. 14.4% vs. 64.3. ±. 19.3%, p. < 0.05) while no significant difference was found in the estimated peak D2 receptor occupancy between them (75.4. ±. 8.7% vs. 72.1. ±. 9.9%, p. = 0.07). When the analyses were separately conducted for the three drugs, there were no significant differences in estimated peak or trough D2 occupancy although the values were consistently numerically higher among those developing involuntary movements. Conclusion: Greater dopamine D2 receptor blockade with antipsychotics at trough might increase the risk of tardive involuntary movements although this finding needs to be replicated in larger trials.

Objective: The objective of this study was to evaluate the impact of once- versus twice-daily dosing of perphenazine, which has a plasma half-life of 8-12 hours, on clinical outcomes in patients with schizophrenia. Method: Data from phase 1 of the Clinical Antipsychotic Trial of Intervention Effectiveness (CATIE) conducted between January 2001 and December 2004 were used in this post hoc analysis. Patients with schizophrenia (DSM-IV) randomly allocated to treatment with perphenazine were also randomly assigned to once-daily (N = 133) or twice-daily (N = 124) dosing and followed over 18 months. Discontinuation rate and time to discontinuation were used as primary outcomes to compare the 2 groups. The following clinical outcomes were analyzed as secondary measures: efficacy - Positive and Negative Syndrome Scale, Clinical Global Impressions-Severity scale, Calgary Depression Scale for Schizophrenia, and Drug Attitude Inventory and safety/ tolerability - Abnormal Involuntary Movement Scale, Barnes Akathisia Rating Scale, Simpson-Angus Scale, and body weight. Data on treatment-emergent adverse events, concomitant psychotropic medications, and medication adherence (pill count and clinician rating scale) were also analyzed for each group. Results: No significant differences were found in any outcome measures between the once-daily and twice-daily dosing groups, which remained the same when using the mean dose of perphenazine as a covariate. Conclusions: Perphenazine is routinely administered in a divided dosage regimen because of its relatively short plasma half-life. However, the present findings challenge such a strategy, suggesting that once-daily represents a viable treatment option. Results are discussed in the context of more recent evidence that challenges the need for high and continuous dopamine D2 receptor blockade to sustain antipsychotic response.