Comparison of haloperidol and reduced haloperidol plasma levels in four different ethnic populations

Post-therapy plasma concentrations of quetiapine in Taiwanese patients

AIMS

Quetiapine is widely used to treat psychiatric disorders such as major depression, generalized anxiety disorder, dysthymic disorder, and insomnia other than schizophrenia and bipolar disorder. This study investigated the diagnostic distribution of quetiapine use in patients in a psychiatric hospital, the doses of quetiapine prescribed, and the plasma concentrations (Cps) of quetiapine and active metabolites.

METHODS

We enrolled 107 patients who had been prescribed quetiapine for at least 4 weeks. Diagnoses, demographics, and concomitant medications were recorded. Blood sampling was performed in the morning, approximately 12 h after the before-bed dose of quetiapine.

RESULTS

Diagnoses comprised schizophrenia (n = 25), bipolar disorder (n = 51), major depression (n = 15), dysthymic disorder (n = 9), and others (n = 7). The daily dose (DD) of quetiapine ranged from 25 to 800 (175.9 ± 184.4) mg, with the mean Cp being 105.6 ± 215.3 ng/ml, with a mean Cps/DD ratio of 0.58 ± 0.55 ng/ml/mg. There was a moderate positive linear correlation between the dose and Cps of quetiapine (r = 0.60), and the interpatient variation in Cps/DD ratio was up to 26-fold.

CONCLUSION

Quetiapine is used in various doses to treat many psychiatric disorders other than psychosis, and it is usually prescribed as a secondary antipsychotic for symptoms such as insomnia or agitation. A wide interpatient variation of the Cps/DD ratio was noticed. Patients of East Asian descent may exhibit a 50% to 100% increase in the Cps/DD ratio for quetiapine compared with patients of Western descent.

Racial/Ethnic Differences in the Pharmacokinetics of Antipsychotics: Focusing on East Asians

Empirical clinical studies have suggested that East Asian patients may require lower dosages of psychotropic drugs, such as antipsychotics, lithium, and antidepressants, than non-Asians. Both the pharmacokinetic and pharmacodynamic properties of a drug can affect the clinical response of an illness. The levels of antipsychotics used for the treatment of schizophrenia may affect patient clinical responses; several factors can affect these levels, including patient medication adherence, body weight (BW) or body mass index, smoking habits, and sex. The cytochrome P450 (CYP) system is a major factor affecting the blood levels of antipsychotics because many antipsychotics are metabolized by this system. There were notable genetic differences between people of different races. In this study, we determined the racial or ethnic differences in the metabolic patterns of some selected antipsychotics by reviewing therapeutic drug monitoring studies in East Asian populations. The plasma concentrations of haloperidol, clozapine, quetiapine, aripiprazole, and lurasidone, which are metabolized by specific CYP enzymes, were determined to be higher, under the same daily dose, in East Asian populations than in Western populations.

Therapeutic Drug Monitoring of Paliperidone in Patients With Schizophrenia in Taiwan

BACKGROUND

The blood level of antipsychotics affects clinical responses to the drug; it can be influenced by race and several individual factors. This study analyzed the therapeutic plasma concentrations (Cps) of paliperidone for both oral and long-acting injectable (LAI) formulations in clinical samples from Taiwanese patients.

METHODS

Patients diagnosed with schizophrenia and treated with either oral paliperidone for at least 4 weeks or LAI paliperidone for at least 6 months were enrolled. Blood samples were taken before the morning dose of oral paliperidone or the injection of LAI paliperidone to obtain the trough Cps.

RESULTS

Among the patients in this study, 51 were taking oral paliperidone, and 26 were receiving LAI paliperidone. In the oral group, the mean Cps were 40.2 ± 19.8 ng/mL in patients taking 9 mg/d and 44.2 ± 15.9 ng/mL in those taking 12 mg/d. In the LAI group, the mean Cps were 32.9 ± 12.7 ng/mL in patients receiving 100 mg per 28 days and 49.9 ± 25.9 ng/mL in those receiving 150 mg per 28 days. The mean Cps per daily dose (Cps/DD) were 4.11 ± 1.99 ng/mL/mg in the oral group and 9.24 ± 3.78 ng/mL/mg in the LAI group.

CONCLUSIONS

Under the suggested DD for oral and LAI paliperidone treatment, most Taiwanese patients with schizophrenia can reach the suggested therapeutic Cps range. Wide interindividual differences were observed in the Cps/DD for both the oral (7-fold) and LAI paliperidone (4-fold) groups. Compared with Western reports, no difference was observed in the body weight-adjusted Cps/DD.

Inter-ethnic differences in pharmacokinetics-is there more that unites than divides?

Inter-ethnic variability in pharmacokinetics (PK) has been attributed to several factors ranging from genetic to environmental. It is not clear how current teaching in higher education (HE) reflects what published literature suggests on this subject. This study aims to gain insights into current knowledge about inter-ethnic differences in PK based on reports from published literature and current teaching practices in HE. A systematic literature search was conducted on PubMed and Scopus to identify suitable literature to be reviewed. Insights into inter-ethnic differences in PK teaching among educators in HE and industry were determined using a questionnaire. Thirty-one percent of the studies reviewed reported inter-ethnic differences in PK, of these, 37% of authors suggested genetic polymorphism as possible explanation for the inter-ethnic differences observed. Other factors authors proposed included diet and weight differences between ethnicities. Most respondents (80%) who taught inter-ethnic difference in PK attributed inter-ethnic differences to genetic polymorphism. While genetic polymorphism is one source of variability in PK, the teaching of genetic polymorphism is better associated with interindividual variabilities rather than inter-ethnic differences in PK as there are no genes with PK implications specific to any one ethnic group. Nongenetic factors such as diet, weight, and environmental factors, should be highlighted as potential sources of interindividual variation in the PK of drugs.

Prescribing of clozapine and olanzapine: dosage, polypharmacy and patient ethnicity

Aims and Method

The aim of this study was to determine the existence and extent of differences in prescribing practice for patients according to ethnic group, with two widely used atypical antipsychotics, olanzapine and clozapine. All in-patient prescription charts were screened and patients receiving olanzapine and clozapine identified. Dosage, antipsychotic co-prescription and race were recorded, along with demographic details, and evaluated using comparative statistical analysis.

Results

Overall, 1441 prescriptions were screened; 328 patients received olanzapine and 200 clozapine. Details of ethnic origin were available for 287 of those prescribed olanzapine and 188 of those prescribed clozapine. There was no significant difference between ethnic groups in age or gender, for either drug. For clozapine, dosage and extent of antipsychotic co-prescription did not differ significantly between ethnic groups; for olanzapine, there was no significant difference in daily dose between the groups, but co-prescription was significantly more common in Black (33%) than in White patients (20%; P=0.023).

Clinical Implications

Important differences in the prescription of olanzapine and clozapine between ethnic groups are uncommon, but demand further investigation. Larger studies incorporating additional baseline details such as diagnosis and body weight are called for.

The efficacy and safety of once-daily quetiapine extended release in patients with schizophrenia switched from other antipsychotics: an open-label study in Chinese population

BACKGROUND

Non-adherence to antipsychotic medication in schizophrenic patients is common and associated with symptom relapse and poorer long-term outcomes. The risk factors for treatment non-adherence include dosing frequency and complexity. Besides, slower dose titration in an acute schizophrenic episode may lead to attenuated efficacy. Therefore, the convenient dosage regimen and rapid initiation scheme of quetiapine extended release (XR) were expected to provide better effectiveness and promote adherence in patients with schizophrenia. This study was implemented to assess the efficacy and safety of once-daily quetiapine XR in schizophrenic patients with switched from other antipsychotics which were suboptimal due to insufficient efficacy or tolerability.

METHODS

This was a 12-week, open-label study conducted in the Chinese population in Taiwan. Patients who had a score of 4 (moderate) or greater on any of the 7 items of the Positive and Negative Syndrome Scale (PANSS) Positive Symptom Subscale and needed to switch from previous antipsychotics were recruited. Quetiapine XR was administered at 300 mg on day 1, 600 mg on day 2 and up to 800 mg after day 2. From day 8 until the end of the study, the dose of quetiapine XR was adjusted within 400-800 mg per day, depending on the clinical response and tolerance of the patients. The variable of the primary outcome was the change from baseline to Week 12 in PANSS total and subscale scores. Secondary outcome was the baseline-to-endpoint difference in the Clinical Global Impression-Severity (CGI-S) scores of the participants.

RESULTS

Sixty-one patients were recruited and 55.7% of them completed the study. The mean changes in the PANSS total score and CGI-S score showed significant improvement (-18.4, p < .001 and -1.0, p < .001, respectively). Four patients (6.7%) experienced adverse events including headache, exacerbation of psychosis and dysuria. The use of concomitant anticholinergics decreased from 15.0% to 8.3%.

CONCLUSIONS

The results of our investigation implicated that quetiapine XR was an effective and well tolerated alternative for Chinese schizophrenic patients with previous suboptimal treatment. Future large-scale studies are warranted to validate our results.

TRIAL REGISTRATION

ClinicalTrials.gov ID NCT02142556 . Registered 15 May 2014.

Effectiveness and safety of olanzapine in the treatment of schizophrenia among Asian patients switching from conventional antipsychotics

OBJECTIVES

The objectives of this study were: (1) to investigate, in a clinical practice setting, the effectiveness of olanzapine in the treatment of schizophrenia among partially-responding, symptomatic Asian patients who switch from conventional antipsychotic treatment, (2) to assess the safety of olanzapine and (3) to assess the change in quality of life in Asian patients with schizophrenia who switch to olanzapine.

METHODS

Effectiveness, safety and quality of life were assessed in outpatients with schizophrenia (n=1267) who lacked symptomatic control with conventional antipsychotics and were switched to olanzapine therapy. Data for this prospective, observational study were collected for 12 months from Asian patients in China, Hong Kong, the Philippines, South Korea and Taiwan.

RESULTS

Significant clinical improvements (P<0.05) were observed following 12 months of olanzapine treatment and 87.3% of the subjects responded to treatment at endpoint (i.e. Brief Psychiatric Rating Scale Total score reduced by > or =30% relative to baseline; last observation carried forward). Abnormal involuntary movements (mean change in Abnormal Involuntary Movement Scale: -3.20, P<0.001) and quality of life were significantly improved in patients treated with olanzapine. However, some patients experienced significant weight gain (3.60+/-4.50 kg, P<0.001) with olanzapine treatment, relative to baseline.

CONCLUSIONS

This study shows that switching to olanzapine may be effective in improving symptoms, may be well-tolerated and may improve the quality of life in Asian patients who are only partially responsive to treatment with conventional antipsychotics. The pragmatic design and naturalistic setting of this large study make the findings relevant for treating patients from some Asian countries in routine clinical practice.

Risk of Extrapyramidal Syndrome in Schizophrenic Patients Treated with Antipsychotics: A Population-based Study

To compare the prevalence of extrapyramidal syndrome (EPS) between the first-generation antipsychotics (FGAs) and second-generation antipsychotics (SGAs), the co-prescribing rate of anti-Parkinson drugs (APDs) of each antipsychotic drug was analyzed using population database. Fourteen antipsychotics had been prescribed during the 5-year study period. Among the SGAs, quetiapine had the lowest crude co-prescribing rate of APDs (27.09%), whereas risperidone had the highest rate (66.50%). Among the FGAs, thioridazine and loxapine had the lowest (60.99%) and highest rates (96.35%), respectively. The rankings of the co-prescribing rate of APDs among antipsychotics, in increasing order, were quetiapine, clozapine, olanzapine, thioridazine, zotepine, chlorpromazine, risperidone, sulpiride, clotiapine, flupentixol, haloperidol, zuclopentixol, trifluoperazine, and loxapine. The results indicate that the risk of EPS appears to be lower in SGAs than in FGAs; however, the considerably high rate of EPS in some of the newer generation of antipsychotics warrants clinical attention.

Olanzapine in Chinese treatment-resistant patients with schizophrenia: an open-label, prospective trial

The role of olanzapine in treatment-resistant schizophrenia has still not been clearly resolved. In addressing this issue, the current report presents an open-label, prospective, 13 week trial with olanzapine use in Chinese schizophrenic patients who were resistant to more than two different classes of antipsychotics during a minimal 4 week treatment period for each antipsychotic drug at adequate dosage. Fifty-one inpatients were recruited after a cross-titration period and given 10-25 mg of olanzapine daily, without any concomitant antipsychotic medication. Patients were evaluated with the Brief Psychotic Rating Scale (BPRS), the Positive and Negative Symptoms Scale, the Clinical Global Impression Scale (CGI), the Abnormal Involuntary Movement Scale, the Simpson-Angus scale, and the Barnes Akathisia Scale. The olanzapine-treated patients showed significant improvement in both the positive and negative symptoms of schizophrenia by the end of the study. Overall, 20 of 51 (39.2%) responded to 10-25 mg of olanzapine per day as measured by the BPRS and CGI scores. Five patients dropped out due to the worsening of their psychotic symptoms, two patients discontinued owing to poor drug compliance, and the remaining patient complained of a lack of efficacy. Extrapyramidal side-effects were mild, and anticholinergic medications required has decreased. The present open study suggests that olanzapine may be effective and well-tolerated in Chinese treatment-resistant schizophrenic patients. Further double-blinded trials are needed to confirm this result.

Factors affecting serum haloperidol level assessed by longitudinal therapeutic monitoring

1. Since the development of a kit for the assay of haloperidol by enzyme immunoassay, therapeutic monitoring of haloperidol has been utilised in Japan for several years. By retrospectively analysing the accumulated data, this study was carried out to investigate the factors affecting haloperidol level. Especially, the effects of enzyme-inducing comedications were analysed in relation to serum gamma-glutamyltransferase (GGT) level, which has been measured simultaneously with haloperidol. Serum haloperidol level measurements were obtained from medical records of inpatients on multiple medications (n = 102). For each subject, average haloperidol level was computed during the same prescription and doses. The effects of age, sex, smoking status, and the coadministration of carbamazepine and barbiturates (including phenobarbital, amobarbital and pentobarbital) were analysed using correlation, between-group comparison and multiple regression analysis. Separately, the effect of comedications on haloperidol and GGT levels were analysed individually in a small number of patients (n = 5) who had received those comedications intermittently. Significant lowering of serum haloperidol level by the coadministration of carbamazepine and/or barbiturates was observed. The coadministration was also correlated with the elevated GGT level in between-group comparison. In the separate analysis, the change in haloperidol level was correlated with the change in GGT level in some individuals but not in others. None of the other clinical factors investigated in the study showed significant effect on haloperidol level. This study suggests that the lowering of haloperidol level and the elevation of GGT level may often occur coincidentally by the coadministration of enzyme-inducing drugs. However, whether there is a causal relationship between these phenomena and whether elevated serum GGT level could serve as a clinically useful marker need to be clarified by further basic pharmacological research.

Pharmacogenetics and psychopharmacotherapy

Response to drugs can vary between individuals and between different ethnic populations. The biological (age, gender, disease and genetics), cultural and environmental factors which contribute to these variations are considered in this review. The most important aspect is the genetic variability between individuals in their ability to metabolize drugs due to expression of 'polymorphic' enzymes. Polymorphism enables division of individuals within a given population into at least two groups, poor metabolisers (PMs) and extensive metabolisers (EMs) of certain drugs. The two most extensively studied genetic polymorphisms are those involving cytochrome P450 2D6 (CYP2D6) and CYP2C19. CYP2D6 metabolizes a number of antidepressants, antipsychotics, beta-adrenoceptor blockers, and antiarrhythmic drugs. About 7% of Caucasians and 1% of Asians are PMs of CYP2D6 substrates. CYP2C19 enzyme participates in the metabolism of omeprazole, propranolol and psychotropic drugs such as hexobarbital, diazepam, citalopram, imipramine, clomipramine and amitriptyline. The incidence of PMs of CYP2C19 substrates is much higher in Asians (15-30%) than in Caucasians (3-6%). Variations in metabolism of psychotropic drugs result in variations in their pharmacokinetic parameters. This may lead to clinically significant intra- and inter-ethnic differences in pharmacological responses. Such variations are discussed in this review. Differential receptor-mediated response may play a role in ethnic differences in responses to antipsychotics and tricyclic antidepressants, but such pharmacodynamic factors remain to be systematically investigated. The results of studies of ethnic differences in response to psychopharmacotherapy appear to be discrepant, most probably due to limitations of study design, small sample size, inadequately defined study sample, and lack of control of confounding factors. The clinical value of understanding pharmacogenetics is in its use to optimize therapeutic efficacy, to prevent toxicity of those drugs whose metabolism is catalysed by polymorphic isoenzymes, and to contribute to the rational design of new drugs. Finally, applications and impact of pharmacogenetics in the field of psychopharmacotherapy are discussed.

Dose-dependent reduced haloperidol/haloperidol ratios: influence of patient-related variables

Plasma reduced haloperidol (RH) concentrations or RH to haloperidol (HL) ratios have been suggested to be important in determining the clinical efficacy and extrapyramidal side effects of HL. In this study, we measured the steady-state plasma HL and RH levels by high performance liquid chromatography and analyzed the effects of various variables (dose, gender, age, and body weight) on RH/HL ratios in four dose groups of Chinese schizophrenic inpatients: 10 mg/day (n = 84), 20 (n = 111), 30 (n = 29), and 60 (n = 55). In addition, the polymorphic distribution of RH/HL ratios, suggested by previous investigators, was further tested in each dosage group (for controlling the potential dosage effect on RH/HL ratios). As a result, both age and body weight could influence RH/HL ratios. Each year increase in age (after adjusting the effects of gender, body weight, and dosage) would elevate the RH/HL ratio by 0.0067 (P < 0.0001). On the other hand, after adjusting gender, age, and dosage effects, each kg increment in body weight would decrease the RH/HL ratio by 0.0044 (P < 0.01). Gender did not influence the ratio. Furthermore, the high dosage groups had higher RH/HL ratios (even with other variables being controlled). In comparison with the 10 mg group, the 60 mg group exhibited a higher mean RH/HL ratio by 0.84 (P < 0.0001) and the 30 mg group did by 0.31 (P < 0.0001). The 20 mg group was almost equal to the 10 mg group in RH/HL ratios. Besides, at each dosage group, the frequency distribution of RH/HL ratios seemed to be predominantly unimodal with a small proportion of extreme outliers. The results of this study clearly indicate that aging or a high dose (> or = 30 mg/day) of HL could raise the plasma RH/HL ratio, while an increasing body weight would reduce that. In contrast, gender does not affect the ratios.

Pharmacoclinical correlations in schizophrenic patients treated with haloperidol decanoate: clinical evaluations, concentrations of plasma and red blood cell haloperidol and its reduced metabolite, and plasma homovanillic acid

1. The aim of this open study was to determine whether a more rational therapeutic approach could be devised for psychotic patients (n = 11) treated for long periods with long-acting (LA) haloperidol. The mean multiplication factor for the transition from the oral formulation to the long-acting one was 12.8 (10.4, standard deviation), lower than the theoretically recommended factor of 20. 2. The best dose (mg/kg)-concentration correlations were found for haloperidol (HAL) and reduced HAL (RHAL) in the red blood cells (RBC) (representative of the free drug fraction) rather than in the plasma of patients that had attained the steady state (at the third cycle and afterwards) 3. Pharmacokinetic analyses were conducted at the same time as clinical evaluations, grading using the BPRS and determinations of plasma levels of total, free and conjugated homovanillic acid (HVA), a marker of central dopaminergic activity. 4. A between groups comparison at the steady state (patients (n = 20) with oral administration and the above patients (n = 11) with long-acting form of HAL), showed that the plasma and RBC RHAL/HAL ratios of long-acting HAL decreased significantly (p < 0,005) in comparison with oral administration, at least by half. 5. Plasma HVA values complete the information provided by plasma and more especially RBC HAL and RHAL levels. All these results taken together, as substantiated by the clinical assessment scales (BPRS), assure a better pharmacoclinical surveillance and can be predictive of a patient's response.

Racial, ethnic and gender differences in response to medicines

In recent years, researchers have found significant differences among racial, ethnic and gender groups in the ways they respond to and metabolize drugs, and experience side effects. Most studies have focused on cardiovascular, psychotropic and central nervous system drugs. Alcohol, antihistamines and analgesics are other agents with varying effects among different racial, ethnic and gender groups. The Food and Drug Administration (FDA) noted last year that Asian-Americans show increased sensitivity to beta blockers. It also observed that African-Americans are less responsive to ACE inhibitors. Gender differences in drug therapy seem to basically evolve around psychotropic drugs. Environmental, cultural and genetic factors are involved in determining response to medicines in different racial, ethnic and gender groups. Continued research in this area will undoubtedly reveal significant information regarding racial, ethnic and gender differences in response to drugs. These developments will impact on how clinical trials are conducted and challenge conventional thoughts regarding restricted formularies.

Nonlinear relationship between circulating concentrations of reduced haloperidol and haloperidol: evaluation of possible mechanisms

In patients taking haloperidol (HP), circulating concentrations of reduced haloperidol (RHP increase disproportionately to the dose or concentration of the parent drug. In the current study, we tested the hypothesis that the nonlinearity is due to preferential saturation of the reoxidation of RHP to HP, and two factors that could amplify the nonlinearity-concentration-dependent binding of RHP by plasma proteins, or by red blood cells. In 25 patients with schizophrenia who were taking HP, the unbound fraction of HP (0.085 +/- 0.016) and RHP (0.244 +/- 0.026) in plasma, and the blood:plasma ratio for each compound were independent of their concentration. Thus, saturable binding of RHP to plasma proteins or red blood cells can be excluded. HP reductase and RHP oxidase activity were measured in human liver cytosol and microsomal fractions, respectively. Because ketone reductase-catalysed formation of RHP is stereospecific, we examined each enantiomer of RHP separately. The Vmax for the oxidation of the S(-) and R(+) RHP enantiomers in four livers was 0.23 +/- 0.15 and 0.60 +/- 0.32 mumol/g protein per min (mean +/- SD), respectively. The Km was 110 +/- 40 and 70 +/- 10 microM, respectively. In contrast, HP reductase activity displayed greater capacity and was not saturable. The rate of production of RHP at a HP concentration of 122 microM (the limit of HP solubility) in the same livers was 2.6 +/- 0.7 mumol/g protein per min. Despite the observed nonlinearity between the enzymatic pathways in vitro, RHP concentrations in vivo are 2-3 orders of magnitude lower than the Km for oxidation of each enantiomer of RHP.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma reduced haloperidol/haloperidol ratios in schizophrenic patients treated with high dosages of haloperidol

Plasma haloperidol (HL) and reduced haloperidol (RH) levels were measured in 60 schizophrenic patients treated with high to very high HL doses of 40-200 mg/day. Plasma samples were obtained at steady-state conditions and 10-12 h after the evening dose and prior to the morning dose. RH/HL ratios were shown to be dose-dependent. In the lowest dose group of 40-45 mg/day, 77% of the patients had RH/HL ratios < 1.0. At the higher dose of 60-80 mg/day, these results were reversed as 79% of the patients had RH/HL ratios > 1.0. All patients with HL doses greater than 100 mg/day had RH/HL ratios > 1.0. All patients safely tolerated the high haloperidol dosages and only five patients had extrapyramidal side effects that were unresponsive to trihexyphenidyl. Therapeutic improvement was not observed in each patient. Based upon the dose-dependent increase in the RH/HL ratios in schizophrenic patients, the possible mechanism of a 'therapeutic' window for HL is discussed.

Reduced haloperidol: a factor in determining the therapeutic benefit of haloperidol treatment?

One of the metabolic pathways of haloperidol (HAL) is the reduction of the molecule at the benzylic ketone to form an alcohol metabolite, known as reduced HAL (RHAL). The basic and clinical pharmacology of RHAL is the subject of this review. The investigation of RHAL in biological samples has been suggested to be important, as the reduced metabolite can be reconverted back to the parent drug and is shown to be 20-50% as potent as HAL in some in vivo neuroleptic tests. Nevertheless, the metabolic reduction/oxidation cycle of the drug is unbalanced. The interconversion process largely favours the reduction of HAL to RHAL but not vice versa. The RHAL/HAL ratios are dose and time dependent. The higher the dose or the longer the duration of treatment, the greater the ratio. The results concerning relationship between plasma RHAL level or RHAL/HAL ratio and clinical response are inconsistent, yet interesting. Some studies in schizophrenic patients have suggested a diminished therapeutic response to HAL when elevated plasma RHAL concentrations or RHAL/HAL ratios are presented. However, this finding has not been replicated by other investigations. Possible interference by RHAL with HAL at dopamine receptors thus reducing the effectiveness of HAL treatment has been suggested by some authors. Measurements of RHAL as well as HAL plasma concentrations for evaluating drug level-clinical response might be necessary in psychiatric patients.