Dose-related plasma levels of clozapine: influence of smoking behaviour, sex and age

Estrogens prevent the hypothalamus-periphery crosstalk induced by olanzapine intraperitoneal treatment in female mice: Effects on brown/beige adipose tissues and liver

Olanzapine (OLA) is a highly obesogenic second-generation antipsychotic (SGA). Recently we demonstrated that, contrarily to OLA oral treatment, intraperitoneal (i.p.) administration resulted in weight loss and absence of hepatic steatosis in wild-type (WT) and protein tyrosine phosphatase 1B (PTP1B)-deficient (KO) male mice. This protection relied on two central-peripheral axes connecting hypothalamic AMPK with brown/inguinal white adipose tissue (BAT/iWAT) uncoupling protein-1 (UCP-1) and hypothalamic JNK with hepatic fatty acid synthase (FAS). Herein, we addressed OLA i.p. treatment effects in WT and PTP1B-KO female mice. Contrarily to our previous results in WT females receiving OLA orally, the i.p. treatment did not induce weight gain or hyperphagia. Molecularly, in females OLA failed to diminish hypothalamic phospho-AMPK or elevate BAT UCP-1 and energy expenditure (EE) despite the preservation of iWAT browning. Conversely, OLA i.p. treatment in ovariectomized mice reduced hypothalamic phospho-AMPK, increased BAT/iWAT UCP-1 and EE, and induced weight loss as occurred in males. Pretreatment of hypothalamic neurons with 17β-estradiol (E2) abolished OLA effects on AMPK. Moreover, neither hypothalamic JNK activation nor hepatic FAS upregulation were found in WT and PTP1B-KO females receiving OLA via i.p. Importantly, this axis was reestablished upon ovariectomy. In this line, E2 prevented OLA-induced phospho-JNK in hypothalamic neurons. These results support the role of estrogens in sex-related dimorphism in OLA treatment. This study evidenced the benefit of OLA i.p. administration in preventing its obesogenic effects in female mice that could offer clinical value.

Clinical and pharmacological factors influencing serum clozapine and norclozapine levels

Background

Clozapine (CLO) is a very effective antipsychotic, whose use is associated with dose-dependent risk of complications. Due to high interindividual variability in CLO metabolism, there is a need to identify factors affecting the blood concentrations of CLO and its active metabolite, norclozapine (NCLO).

Methods

A total of 446 blood samples (collected from 233 women and 213 men, aged from 18 to 77 years) were included in this study and analyzed for CLO and NCLO concentrations. The patients were treated at a psychiatric hospital in Warsaw in the years 2016-2021. Serum CLO and NCLO concentrations were determined with high-performance liquid chromatography coupled to UV.

Results

The following factors were shown to increase serum CLO and NCLO levels: higher CLO dose (p < 0.001), female sex (p < 0.001), nonsmoker status (p < 0.001), the use of more than two additional psychotropic drugs (only in the case of CLO; p = 0.046), concomitant use of beta-blockers (for CLO p = 0.049; for NCLO p < 0.001), and older age (for CLO p < 0.001; for NCLO p = 0.011). Despite the use of CLO at daily doses within the recommended range (200-450 mg), the evaluated serum CLO and NCLO levels were within the therapeutic ranges in only 37% and 75% of cases, respectively, with 5.6% of cases exceeding the CLO toxicity threshold.

Discussion

The use of CLO at recommended doses does not guarantee achieving therapeutic concentrations of CLO or NCLO. Women and nonsmokers were at the highest risk of having toxic CLO levels.

Development and validation of a risk prediction nomogram for disposition of acute clozapine intoxicated patients to intensive care unit

BACKGROUND

Clozapine is an atypical antipsychotic drug used for the treatment of refractory schizophrenia. It is reported as the most toxic in its class. Using serum clozapine level as a severity indicator is doubtful and unfeasible, particularly in low resourced countries.

METHODS

This is an extended two-phase retrospective study that utilized medical records of patients diagnosed with acute clozapine intoxication and admitted to Tanta University Poison Control Center, Egypt during the past 6 years. Two hundred and eight medical records were used to establish and validate a nomogram for predicting the need for intensive care unit (ICU) admission in acute clozapine intoxicated patients.

RESULTS

A reliable simple bedside nomogram was developed and proved its significant ability to predict the need for ICU admission, with an area under the curve (AUC) of 83.9% and 80.8% accuracy. It encompassed the age of admitted patients (AUC = 64.8%, p = .003), respiratory rate (AUC = 74.7%, p < .001), O₂ saturation (AUC = 71.7%, p < .001), and random blood glucose level upon admission (AUC = 70.5%, p < .001). External validation of the proposed nomogram showed a high AUC (99.2%) with an overall accuracy of 96.2%.

CONCLUSION

There is a need to develop a reliable objective tool predicting the severity and need for ICU admission in acute clozapine intoxication. The proposed nomogram is a substantially valuable tool to estimate ICU admission probabilities among patients with acute clozapine intoxication and will help clinical toxicologists make rapid decisions for ICU admission, especially in countries with low resources.

Second to none: rationale, timing, and clinical management of clozapine use in schizophrenia

Despite its enduring relevance as the single most effective and important evidence-based treatment for schizophrenia, underutilization of clozapine remains considerable. To a substantial degree, this is attributable to a reluctance of psychiatrists to offer clozapine due to its relatively large side-effect burden and the complexity of its use. This underscores the necessity for continued education regarding both the vital nature and the intricacies of clozapine treatment. This narrative review summarizes all clinically relevant areas of evidence, which support clozapine's wide-ranging superior efficacy - for treatment-resistant schizophrenia (TRS) and beyond - and make its safe use eminently feasible. Converging evidence indicates that TRS constitutes a distinct albeit heterogeneous subgroup of schizophrenias primarily responsive to clozapine. Most importantly, the predominantly early onset of treatment resistance and the considerable decline in response rates associated with its delayed initiation make clozapine an essential treatment option throughout the course of illness, beginning with the first psychotic episode. To maximize patients' benefits, systematic early recognition efforts based on stringent use of TRS criteria, a timely offer of clozapine, thorough side-effect screening and management as well as consistent use of therapeutic drug monitoring and established augmentation strategies for suboptimal responders are crucial. To minimize permanent all-cause discontinuation, re-challenges after neutropenia or myocarditis should be considered. Owing to clozapine's unique efficacy, comorbid conditions including substance use and most somatic disorders should not dissuade but rather encourage clinicians to consider clozapine. Moreover, treatment decisions need to be informed by the late onset of clozapine's full effects, which for reduced suicidality and mortality rates may not even be readily apparent. Overall, the singular extent of its efficacy combined with the high level of patient satisfaction continues to distinguish clozapine from all other available antipsychotics.

Delineating gene-environment effects using virtual twins of patients treated with clozapine

Studies that focus on individual covariates, while ignoring their interactions, may not be adequate for model-informed precision dosing (MIPD) in any given patient. Genetic variations that influence protein synthesis should be studied in conjunction with environmental covariates, such as cigarette smoking. The aim of this study was to build virtual twins (VTs) of real patients receiving clozapine with interacting covariates related to genetics and environment and to delineate the impact of interacting covariates on predicted clozapine plasma concentrations. Clozapine-treated patients with schizophrenia (N = 42) with observed clozapine plasma concentrations, demographic, environmental, and genotype data were used to construct VTs in Simcyp. The effect of increased covariate virtualization was assessed by performing simulations under three conditions: "low" (demographic), "medium" (demographic and environmental interaction), and "high" (demographic and environmental/genotype interaction) covariate virtualization. Increasing covariate virtualization with interaction improved the coefficient of variation (R² ) from 0.07 in the low model to 0.391 and 0.368 in the medium and high models, respectively. Whereas R² was similar between the medium and high models, the high covariate virtualization model had improved accuracy, with systematic bias of predicted clozapine plasma concentration improving from -138.48 ng/ml to -74.65 ng/ml. A high level of covariate virtualization (demographic, environmental, and genotype) may be required for MIPD using VTs.

Successful rechallenge after clozapine-associated myocarditis

Clozapine is a highly effective medication used in management of treatment-resistant schizophrenia. Clozapine-associated myocarditis (CAM) is a rare but increasingly recognised complication of clozapine titration. Following an episode of CAM, clinicians can face a challenging dilemma of balancing the risks of recurrent myocarditis against the harms of ongoing psychosis. We describe the case of a woman in her 60s who developed acute myocarditis during clozapine titration and was then cautiously rechallenged with a successful outcome.

Clinical and genetic influencing factors on clozapine pharmacokinetics in Tunisian schizophrenic patients

Clozapine (Clz) is an atypical antipsychotic, which its pharmacokinetics can be influenced by several factors. The CYP1A2 and CYP2C19, major enzymes implicated in Clz metabolism, present an interethnic variation on their activity caused by single nucleotide polymorphisms (SNPs). The present study investigated the influence of genetic and nongenetic factors on Clz pharmacokinetics in a southern Mediterranean population. We included adult Tunisian schizophrenic patients having received Clz and undergone a therapeutic drug monitoring (TDM) of Clz by morning C0 monitoring. The genomic DNA was extracted using a salting-out procedure. CYP1A2*1F (rs762551;-163C>A), CYP1A2*1C (rs2069514;-3860 G>A) and CYP 2C19*2 (rs4244285; 681G>A) was analyzed using PCR-RFLP. Fifty-one patients were enrolled in the study. The mutant allele (CYP1A2*1F) was the most frequently detected (58.8%). For CYP1A2*1F, Clz dose-normalized (C0/D ratio) was as high as 1.28 ± 0.37 in CC versus 0.67 ± 0.32 ng mL^-1 per mg day^-1 in AA group (p < 0.001). The influence of genetic (CYP1A2*1F, CYP1A2*1C and CYP2C19*2) and nongenetic parameters (age, weight, gender, tobacco, coffee, and alcohol consumption) on the variation of the Clz C0/D ratio was investigated. Only the CYP1A2*1 F polymorphism correlates significantly with the Clz C0/D variation and could explain 24% of its variability. Our data support a critical role of the CYP1A2 -163C>A on the variation of Clz exposure in Tunisian schizophrenic patients. Considering its narrow therapeutic range, CYP1A2 genotyping combined with TDM of Clz may improve efficacy and safety of this drug. Further studies are needed to investigate this issue.

Selective Serotonin Reuptake Inhibitors and Clozapine: Clinically Relevant Interactions and Considerations

The monoamine hypothesis of depression attributes the symptoms of major depressive disorders to imbalances of serotonin, noradrenaline, and dopamine in the limbic areas of the brain. The preferential targeting of serotonin receptor (SERT) by selective serotonin reuptake inhibitors (SSRIs) has offered an opportunity to reduce the range of these side effects and improve patient adherence to pharmacotherapy. Clozapine remains an effective drug against treatment-resistant schizophrenia, defined as failing treatment with at least two different antipsychotic medications. Patients with schizophrenia who display a constellation of negative symptoms respond poorly to antipsychotic monotherapy. Negative symptoms include the diminution of motivation, interest, or expression. Conversely to the depressive symptomology of interest presently, supplementation of antipsychotics with SSRIs in schizophrenic patients with negative symptoms lead to synergistic improvements in the function of these patients. Fluvoxamine is one of the most potent inhibitors of CYP1A2 and can lead to an increase in clozapine levels. Similar increases in serum clozapine were detected in two patients taking sertraline. However, studies have been contradictory as well, showing no such increases, which are worrying. Clinicians should be aware that clozapine levels should be monitored with any coadministration with SSRIs.

Physiologically-based pharmacokinetic model for clozapine in Korean patients with schizophrenia

Clozapine has been used as a treatment of schizophrenia. Despite its large interindividual variability, few reports addressed the physiologically-based pharmacokinetic modeling and simulation (PBPK M&S) of clozapine in patients. This study aimed to develop a PBPK M&S of clozapine in Korean patients with schizophrenia. PBPK modeling for clozapine was constructed using a population-based PBPK platform, the SimCYP^® Simulator (V19; Certara, Sheffield, UK). The PBPK model was developed by optimizing the physiological parameters of the built-in population and compound libraries in the SimCYP^® Simulator. The model verification was performed with the predicted/observed ratio for pharmacokinetic parameters and visual predictive checks (VPCs) plot. Simulations were performed to predict toxicities according to dosing regimens. From published data, 230 virtual trials were simulated for each dosing regimen. The predicted/observed ratio for the area under the curve and peak plasma concentration was calculated to be from 0.78 to 1.34. The observation profiles were within the 5th and 95th percentile range with no serious model misspecification through the VPC plot. A significant impact on age and gender was found for clozapine clearance. The simulation results suggested that 150 mg twice a day and 150 mg three times a day of clozapine have toxicity concerns. In conclusion, a PBPK model was developed and reasonable parameters were made from the data of Korean patients with schizophrenia. The provided model might be used to predict the pharmacokinetics of clozapine and assist dose adjustment in clinical settings.

Association of clozapine-related metabolic disturbances with CYP3A4 expression in patients with schizophrenia

Clozapine is effective in treatment-resistant schizophrenia; however, adverse effects often result in discontinuation of clozapine therapy. Many of the side-effects are associated with pharmacokinetic variations; therefore, the expression of major clozapine-metabolizing enzymes (CYP1A2, CYP3A4) in patients may predict development of adverse effects. In patients with schizophrenia (N = 96), development of clozapine concentration-dependent metabolic side-effects was found to be associated with pharmacokinetic variability related to CYP3A4 but not to CYP1A2 expression. In low CYP3A4 expressers, significant correlation was detected between fasting glucose level and clozapine concentration; moreover, the incidence of abnormal glucose level was associated with exaggerated clozapine concentrations (> 600 ng/ml). In low CYP3A4 expressers, exaggerated concentrations were more frequently observed than in normal/high expressers. Moderate/high risk obesity (BMI ≥ 35) more frequently occurred in low CYP3A4 expresser patients than in normal/high expressers. In patients with normal/high CYP3A4 expression and consequently with extensive clozapine-metabolizing capacity, norclozapine/clozapine ratio correlated with fasting glucose levels, triglyceride concentrations and BMI. Low CYP3A4 expression often resulting in exaggerated clozapine concentrations was considered to be as an important risk factor for some concentration-dependent adverse effects as normal/high CYP3A4 expression evoking high norclozapine/clozapine ratios. CYP3A4-status can identify patients with increased risk for metabolic side-effects and prevent their development by careful therapeutic strategy.

Association Between N-Desmethylclozapine and Clozapine-Induced Sialorrhea: Involvement of Increased Nocturnal Salivary Secretion via Muscarinic Receptors by N-Desmethylclozapine

Clozapine-induced sialorrhea (CIS) is a common side effect of clozapine. There is no established standard treatment of CIS since the underlying mechanism remains unknown. This study aimed to elucidate the mechanisms involved in CIS. In our clinical study, a prospective observational study evaluated the association between serum and saliva concentrations of clozapine or its metabolites and Drooling Severity and Frequency Scale (DSFS) score. In our in vivo study, we first developed a new CIS animal model; subsequently, we measured salivary secretion and concentrations of clozapine or its metabolites in the animal model. In our in vitro study, we measured the calcium ion (Ca²⁺) response to evaluate the effect of clozapine or its metabolites on human salivary gland cell line (HSY cells) and then examined whether their effect was inhibited by atropine. In our clinical study, serum and saliva N-desmethylclozapine concentrations were significantly correlated with nocturnal DSFS score. In our in vivo study, daily single oral administration of 100 mg/kg clozapine for 7 days significantly increased salivary secretion in rats. Furthermore, N-desmethylclozapine concentrations in serum and submandibular glands of the rats were higher than clozapine concentrations. In our in vitro study, N-desmethylclozapine only elicited an increase in the intracellular Ca²⁺ in HSY cells. N-desmethylclozapine-induced Ca²⁺ responses were inhibited by atropine. These results suggest that N-desmethylclozapine is implicated in CIS by increasing nocturnal salivation via the muscarinic receptors. Moreover, our developed animal model that reflects CIS in clinical condition plays a key role as a bridge between basic and clinical research. SIGNIFICANCE STATEMENT: Clozapine-induced sialorrhea (CIS) is a severe and frequent adverse reaction, but the mechanism underlying CIS is less well understood. This paper reports that N-desmethylclozapine, a metabolite of clozapine, is implicated in CIS by increasing nocturnal salivation via the muscarinic receptors and that oral administration of clozapine at 100 mg/kg once daily for 7 days to rat is the optimum method for establishing the new animal model reflecting the clinical scenario of CIS.

Pharmacokinetic interactions between clozapine and sertraline in smokers and non-smokers

Clozapine is an effective antipsychotic drug for treatment-resistant schizophrenia. Sertraline is a widely prescribed antidepressant and often concomitantly applied to address negative symptoms or depression. However, data on interactions between clozapine and sertraline are inconsistent. The aim of our study was to evaluate pharmacokinetic interactions between clozapine and sertraline analysing a therapeutic drug monitoring database of 1644 clozapine-medicated patients. We compared four groups: non-smokers (n = 250) and smokers (n = 326) with co-medication without known effects on cytochrome P450 and without sertraline, and non-smokers (n = 18) and smokers (n = 17) with sertraline co-medication. Measured and dose-corrected concentrations (C/D) of clozapine were compared between the groups using non-parametrical tests with a significance level of 0.05. Post hoc analyses included pairwise comparisons to account for smoking status. Although we detected significant differences for clozapine levels and C/D values between study groups (P < .001 for Kruskal-Wallis test in both cases), post hoc analyses revealed no differences for concentrations and C/D values of clozapine (P > .05 for Mann-Whitney U test in both cases). A negative correlation between the sertraline dose and the clozapine concentration was found in non-smokers (Spearman's rank correlation, rs = -0.535, P = .048). A potential pharmacokinetic interaction between clozapine and a standard therapeutic sertraline dose seems to be of minor clinical importance.

Smoking Is Associated With Lower Dose-Corrected Serum Concentrations of Escitalopram

BACKGROUND

Tobacco smoking rates in depressive patients are higher compared with the general population. Smoking was demonstrated to accelerate the metabolism of different drugs metabolized by CYP1A2, but possibly also by CYP2C19 and CYP3A4. The principle aim of the present investigation from 2015 to 2018 was to determine the differences in the pharmacokinetics of escitalopram between smokers and nonsmokers.

METHODS

A group of nonsmokers (n = 88) was compared with smokers (n = 36), both receiving escitalopram, using the Mann-Whitney U test. Linear regression analysis was used to account for the impact of escitalopram dose, age, and sex in addition to smoking on the steady-state serum concentration of escitalopram.

RESULTS

Smokers received by mean 17.6% higher doses of escitalopram (P = 0.026) but showed 31.9% lower serum concentrations (P = 0.031). To control for confounders, linear regression analysis showed that dose (P < 0.001), sex (P = 0.03), and smoking tobacco (P = 0.027) did significantly influence serum concentrations of escitalopram with higher levels in women and nonsmokers.

CONCLUSIONS

Notwithstanding higher daily doses, smokers had significantly lower serum concentrations of escitalopram. In concordance with previous results, besides CYP1A2, a possible induction of CYP2C19 and CYP3A4 by tobacco smoke, resulting in lower serum concentrations of escitalopram in smokers than in nonsmokers, is suggested. Therefore, to provide personalized therapy, clinicians should consider smoking status and inform patients on the interactions of smoking and escitalopram metabolism.

Population Pharmacokinetics of Clozapine and Norclozapine and Switchability Assessment between Brands in Uruguayan Patients with Schizophrenia

Clozapine (CZP) is an atypical antipsychotic agent commonly used in the treatment of schizophrenia. It is metabolized primarily by CYP1A2 enzyme, yielding a pharmacologically active metabolite, norclozapine (NCZP). Significant intra- and interindividual pharmacokinetic (PK) variability for CZP and NCZP has been observed in routine therapeutic drug monitoring. So the goal of this study was to evaluate the magnitude and variability of concentration exposure to CZP and its active metabolite NCZP on pharmacokinetic parameters in Uruguayan patients with schizophrenia with a focus on covariates such as cigarette smoking, age, sex, caffeine consumption, brands available of CZP, and comedication using population PK (PPK) modeling methodologies. Patients with a diagnosis of schizophrenia treated with brand-name CZP (Leponex®) for more than a year were included in the study. Then these patients were switched to the similar brand of CZP (Luverina®). Morning predose blood samples for determination of CZP and NCZP using a HPLC system equipped with a UV detector were withdrawn on both occasions at steady state and under the same comedication. Ninety-eight patients, 22 women and 76 men, took part in the study. Mean ± standard deviation for CZP and NCZP concentration was 421 ± 262 ng/mL and 275 ± 180 ng/mL, respectively. After covariate evaluation, only smoking status remained significant in CZP apparent clearance, inducing a mean increment of 32% but with no clinical impact. The results obtained with the two brands of CZP should ensure comparable efficacy and tolerability with the clinical use of either product. Smoking was significantly associated with a lower exposure to CZP due to higher clearance. The results obtained with the two brands commercialized in our country hint a bioequivalence scenario in the clinical setting.

Analysis of smoking behavior on the pharmacokinetics of antidepressants and antipsychotics: evidence for the role of alternative pathways apart from CYP1A2

Smoking is common among psychiatric patients and has been shown to accelerate the metabolism of different drugs. We aimed to determine the effect of smoking on the serum concentrations of psychopharmacological drugs in a naturalistic clinical setting. Dose-corrected, steady-state serum concentrations of individual patients were analyzed retrospectively by linear regression including age, sex, and smoking for amitriptyline (n=503), doxepin (n=198), mirtazapine (n=572), venlafaxine (n=534), clozapine (n=106), quetiapine (n=182), and risperidone (n=136). Serum levels of amitriptyline (P=0.038), clozapine (P=0.02), and mirtazapine (P=0.002) were significantly lower in smokers compared with nonsmokers after correction for age and sex. In addition, the ratios of nortriptyline/amitriptyline (P=0.001) and nordoxepin/doxepin (P=0.014) were significantly higher in smokers compared with nonsmokers. Smoking may not only induce CYP1A2, but may possibly also affect CYP2C19. Furthermore, CYP3A4, UGT1A3, and UGT1A4 might be induced by tobacco smoke. Hence, a different dosing strategy is required among smoking and nonsmoking patients. Nevertheless, the clinical relevance of the results remained unclear.

Relationship between Clozapine-Induced Electroencephalogram Abnormalities and Serum Concentration of Clozapine in Japanese Patients with Treatment-Resistant Schizophrenia

OBJECTIVE

The objective of this study was to investigate the relationship between the serum concentration of clozapine (C-CLZ), Ndesmethylclozapine (N-CLZ) and the daily dose of CLZ (D-CLZ), and the relationships among CLZ and electroencephalogram (EEG) abnormalities.

METHODS

Twenty-eight patients were recruited to this study, but 8 patients were excluded because clozapine was discontinued before the post-treatment measurement of EEG or C-CLZ. Ultimately, 20 patients (6 men, 14 women) with an average age of 36 years were enrolled. The subjects were divided into EEG normal and abnormal groups. C-CLZ and N-CLZ were measured at 4, 12, 26, and 52 weeks after initiating CLZ administration.

RESULTS

All patients had normal baseline EEG signals, and 8 patients showed EEG abnormalities later. There were significant correlations between C-CLZ and D-CLZ, and between N-CLZ and D-CLZ. The C-CLZ/D-CLZ, N-CLZ/D-CLZ, and C-CLZ/N-CLZ ratio were not significantly different between the EEG normal and EEG abnormal groups. The EEG abnormal group had significant higher proportion of patients with high intra-individual variability in their C-CLZ/D-CLZ ratio.

CONCLUSION

There is no relationship between C-CLZ and EEG abnormalities. However, patients with high intra-individual variability in their C-CLZ/D-CLZ ratio had greater possibility of exhibiting EEG abnormalities.

The use of clozapine plasma levels in optimising therapy

Clozapine is well known to be an effective treatment for neuroleptic-resistant schizophrenia. However, its use is complicated by a variable and delayed response and by a range of troublesome adverse effects. Current practice is usually to increase the dose initially to around 450 mg/day and then by small increments to a maximum of 900 mg/day according to response and tolerability. While this method is often successful, it has been suggested that a better way of optimising the dose of clozapine might be to monitor plasma concentrations of the drug.

Variation in the Response of Clozapine Biotransformation Pathways in Human Hepatic Microsomes to CYP1A2- and CYP3A4-selective Inhibitors

The atypical antipsychotic agent clozapine (CLZ) is effective in many patients who are resistant to conventional antipsychotic drugs. Cytochromes P450 (CYPs) 1A2 and 3A4 oxidize CLZ to norCLZ and CLZ N-oxide in human liver. Concurrent treatment with inducers and inhibitors of CYP1A2 modulates CLZ elimination that disrupts therapy. Drug-drug interactions involving CYP3A4 are also significant but less predictable. To further characterize the factors underlying these interactions, we used samples from a cohort of human livers to assess variation in CLZ oxidation pathways in relation to intrinsic CYP3A4 and CYP1A2 activities and the effects of the corresponding selective inhibitors ketoconazole (0.2 and 2 μM) and fluvoxamine (1 and 10 μM). The CYP3A4-selective inhibitor ketoconazole (2 μM) impaired CLZ N-oxide formation in all 14 of the livers used in inhibition studies (≥50% inhibition) while the CYP1A2-selective inhibitor fluvoxamine (10 μM) decreased norCLZ formation in nine. Ketoconazole effectively inhibited CLZ metabolism in five of seven livers that catalysed CYP3A4-dependent testosterone 6β-hydroxylation at or above the median rate and in four other livers with lower intrinsic CYP3A4 activity. Similarly, fluvoxamine (10 μM) readily inhibited CLZ oxidation in seven livers with high CYP1A2-mediated 7-ethoxyresorufin O-deethylation activity (at or above the median) and three livers with lower intrinsic CYP1A2 activity. In three livers, CLZ biotransformation was impaired by both ketoconazole and fluvoxamine, consistent with a major role for both CYPs. These findings suggest that the intrinsic activities of CYPs 1A2 and 3A4 are unrelated to the response to CYP-selective inhibitors and that assessment of the activities in vivo may not assist the prediction of drug-drug interactions.

ABCB1 and ABCC1 single-nucleotide polymorphisms in patients treated with clozapine

Clozapine (CZ) has superior efficacy to other antipsychotic agents in the treatment of schizophrenia and has been extensively used in clinical practice. ATP-binding cassette (ABC) transporter proteins are responsible for the distribution of various molecules as well as drugs across extracellular and intracellular membranes, including the blood-brain barrier. Genetic variations in these proteins can account for differences in treatment response. We investigated the influence of ABCB1 rs1045642 and ABCC1 rs212090 single-nucleotide polymorphisms (SNPs) on CZ serum level, clinical outcome, and changes in body mass index (BMI) in the first year of CZ treatment. These polymorphisms influenced baseline BMI in males (p=0.009 and 0.054, B1 and C1, respectively), changes in BMI in males after 3 (p=0.026, ABCB1) and 12 months (p=0.022, ABCC1) of CZ treatment, and level of diastolic pressure (p=0.002 and 0.051, respectively). The combination of ABCB1 + ABCC1 homozygote SNPs was associated with increased CZ and norclozapine serum levels (p=0.054 and 0.010, respectively). ABC transporter SNPs could be potential biomarkers for CZ-induced weight gain and cardiovascular complications. Further pharmacogenetic research is warranted to help clinicians with their treatment decision, including concomitant use of drugs and prevention of side effects.

Confirmation of metabolites of the neuroleptic drug prothipendyl using human liver microsomes, specific CYP enzymes and authentic forensic samples-Benefit for routine drug testing

Metabolism of the tricyclic azaphenothiazine neuroleptic drug prothipendyl was investigated with in vitro studies using human liver microsomes but also specific isoforms of cytochrome P450 (CYP) enzymes. Identification and analysis of metabolites was done by liquid chromatography (LC) coupled with quadrupole time of flight mass spectrometry (LC-QTOF-MS) as well as triple quadrupole mass spectrometry (LC-QQQ-MS). Results of the herein presented study revealed the proof of various demethylated and oxidized metabolites (-CH₂, -C₂H₄, four derivatives of prothipendyl +O and three derivatives of prothipendyl -CH₂+O). Metabolic reactions of prothipendyl were mainly catalyzed by CYP enzymes CYP1A2, CYP2D6, CYP2C19 and CYP3A4. N-demethyl-prothipendyl was predominantly formed by isoforms CYP2C19 and CYP1A2, while particularly the CYP isoenzyme 3A4 was responsible for the formation of prothipendyl sulfoxide. To confirm the formation of previously identified metabolites in vivo, cardiac blood samples that were tested positive for prothipendyl during routine drug testing and serum and urine samples, collected after a voluntary intake of prothipendyl, were analyzed by LC-QQQ-MS. All metabolites of prothipendyl were proven in these authentic specimens. Neither in serum samples nor in urine samples, a prolonged detectability of metabolites in comparison to prothipendyl could be demonstrated.

Potential Role of Patients' CYP3A-Status in Clozapine Pharmacokinetics

BACKGROUND

The atypical antipsychotic clozapine is effective in treatment-resistant schizophrenia; however, the success or failure of clozapine therapy is substantially affected by the variables that impact the clozapine blood concentration. Thus, elucidating the inter-individual differences in clozapine pharmacokinetics can facilitate the personalized therapy.

METHODS

Since a potential role in clozapine metabolism is assigned to CYP1A2, CYP2C19, CYP2D6 and CYP3A enzymes, the association between the patients' CYP status (CYP genotypes, CYP expression) and clozapine clearance was evaluated in 92 psychiatric patients.

RESULTS

The patients' CYP2C19 or CYP2D6 genotypes and CYP1A2 expression seemed to have no effect on clozapine serum concentration, whereas CYP3A4 expression significantly influenced the normalized clozapine concentration (185.53±56.53 in low expressers vs 78.05±29.57 or 66.52±0.25 (ng/mL)/(mg/kg) in normal or high expressers, P<.0001), in particular that the patients expressed CYP1A2 at a relatively low level. The functional CYP3A5*1 allele seemed to influence clozapine concentrations in those patients who expressed CYP3A4 at low levels. The dose requirement for the therapeutic concentration of clozapine was substantially lower in low CYP3A4 expresser patients than in normal/high expressers (2.18±0.64 vs 4.98±1.40 mg/kg, P<.0001). Furthermore, significantly higher plasma concentration ratios of norclozapine/clozapine and clozapine N-oxide/clozapine were observed in the patients displaying normal/high CYP3A4 expression than in the low expressers.

CONCLUSION

Prospective assaying of CYP3A-status (CYP3A4 expression, CYP3A5 genotype) may better identify the patients with higher risk of inefficiency or adverse reactions and may facilitate the improvement of personalized clozapine therapy; however, further clinical studies are required to prove the benefit of CYP3A testing for patients under clozapine therapy.

How gender affects the pharmacotherapeutic approach to treating psychosis - a systematic review

INTRODUCTION

The effectiveness, effective dosages and side effect profiles of antipsychotic medication differ significantly between the sexes. Areas covered: We present a systematic review of gender-differences in the treatment of psychosis focusing on randomized, controlled trials and meta-analyses. Expert opinion: Despite many years of research, the database on gender-differences affecting the pharmacotherapeutic approach to treating psychosis is insufficient. Currently, the US National Institute of Health encouraged the enrolment of female participants in federally supported phase III clinical trials to increase the data available of female patients. Emerging evidence points to a superior antipsychotic response in women, with men requiring higher dosages. In general, women metabolize drugs differently, resulting in side effects occuring more frequently when compared to men. In any case, women require electrocardiograms or bone density scans as well as diabetes and cardiovascular workups when treated with antipsychotics. Dose adjustments during the menstrual cycle (e.g. to raise antipsychotic doses premenstrually) should be considered. First-generation antipsychotics, drugs that are known to prolong QTc interval and increase prolactin levels should be avoided in postmenopausal female patients. Furthermore, the effects of antipsychotics during pregnancy and breastfeeding have been investigated insufficiently, and more research is urgently needed.

The significance of sampling time in therapeutic drug monitoring of clozapine

OBJECTIVE

Therapeutic drug monitoring (TDM) of clozapine is standardized to 12-h postdose samplings. In clinical settings, sampling time often deviates from this time point, although the importance of the deviation is unknown. To this end, serum concentrations (s-) of clozapine and its metabolite N-desmethyl-clozapine (norclozapine) were measured at 12 ± 1 and 2 h postdose.

METHOD

Forty-six patients with a diagnosis of schizophrenia, and on stable clozapine treatment, were enrolled for hourly, venous blood sampling at 10-14 h postdose.

RESULTS

Minor changes in median percentage values were observed for both s-clozapine (-8.4%) and s-norclozapine (+1.2%) across the 4-h time span. Maximum individual differences were 42.8% for s-clozapine and 38.4% for s-norclozapine. Compared to 12-h values, maximum median differences were 8.4% for s-clozapine and 7.3% for s-norclozapine at deviations of ±2 h. Maximum individual differences were 52.6% for s-clozapine and 105.0% for s-norclozapine. The magnitude of s-clozapine differences was significantly associated with age, body mass index and the presence of chronic basophilia or monocytosis.

CONCLUSION

The impact of deviations in clozapine TDM sampling time, within the time span of 10-14 h postdose, seems of minor importance when looking at median percentage differences. However, substantial individual differences were observed, which implies a need to adhere to a fixed sampling time.

Effect of smoking on the pharmacokinetics of inhaled loxapine

Background:

Loxapine inhalation powder delivered by a hand-held device as a thermally generated aerosol (ADASUVE) was recently approved in the United States and European Union for use in the acute treatment of agitation in patients with bipolar disorder or schizophrenia. As smokers comprise a large subpopulation of these patients, and many antipsychotic drugs require dose adjustments for smokers, the objective of this study was to compare the pharmacokinetics of inhaled loxapine administered to smokers and nonsmokers.

Methods:

Pharmacokinetics and sedation pharmacodynamics using a visual analog scale were studied in 35 male and female adult subjects (18 nonsmokers and 17 smokers) following a single dose of 10 mg of inhaled loxapine. Blood samples were drawn at predose, 30 seconds, 1, 2, 3, 10, 30, and 60 minutes, and 2, 6, 12, and 24 hours after dosing. Loxapine and 8-OH-loxapine were analyzed using reverse-phase liquid chromatography coupled with a tandem mass spectrometer. Pharmacokinetic parameters assessed included C_max, T_max, AUC_inf, and T_1/2 for loxapine and 8-OH-loxapine. Geometric mean ratios (GMRs) were determined for smokers to nonsmokers.

Results:

Loxapine C_max was similar in smokers and nonsmokers with a GMR of 99.0%. The median loxapine T_max was 1.88 and 1.01 minutes for nonsmokers and smokers, respectively. Loxapine AUC_inf and AUC_last values in nonsmokers were comparable with smokers (GMRs of 85.3% and 86.7%, respectively). A slight decrease in the observed mean terminal half-life values was observed for smokers (6.52 hours for smokers and 7.30 hours for nonsmokers).

Conclusions:

Sedation profiles and visual analog scale scores at each time point were similar for nonsmokers and smokers. It was concluded that inhaled loxapine does not require dosage adjustment based on smoking behavior.

Genetic and Clinical Factors Affecting Plasma Clozapine Concentration

OBJECTIVE

To assess (1) the variance of plasma clozapine levels; (2) the relative importance of sex, smoking habits, weight, age, and specific genetic variants of cytochrome P450 1A2 (CYP1A2), uridine diphosphate glucuronosyltransferase 1A4 (UGT1A4), and multidrug resistance protein 1 (MDR1) on plasma levels of clozapine; and (3) the relation between plasma clozapine levels, fasting glucose levels, and waist circumference.

METHOD

There were 113 patients on clozapine treatment recruited from psychosis outpatient clinics in Stockholm County, Sweden. Patients had genotype testing for single nucleotide polymorphisms: 2 in MDR1, 3 in CYP1A2, and 1 in UGT1A4. Multiple and logistic regression were used to analyze the relations.

RESULTS

There was a wide variation in plasma concentrations of clozapine (mean = 1,615 nmol/L, SD = 1,354 nmol/L), with 37% of the samples within therapeutic range (1,100-2,100 nmol/L). Smokers had significantly lower plasma clozapine concentrations than nonsmokers (P ≤ .03). There was a significant association between the rs762551 A allele of CYP1A2 and lower plasma clozapine concentration (P ≤ .05). Increased fasting glucose level was 3.7-fold more frequent in CC and CA genotypes than AA genotype (odds ratio = 0.27; 95% confidence interval, 0.10-0.72). There was no significant relation between higher fasting glucose levels, larger waist circumference, and higher clozapine levels.

CONCLUSIONS

It is difficult to predict plasma clozapine concentration, even when known individual and genetic factors are considered. Therefore, therapeutic drug monitoring is recommended in patients who are treated with clozapine.

Smoking and weight among patients using clozapine

BACKGROUND

Both obesity and smoking are common in schizophrenia patients taking clozapine, causing cardiovascular disease and premature deaths.

METHODS

Two hundred and thirty-seven patients with schizophrenia or related psychoses treated with clozapine completed the Liverpool University Neuroleptic Assessment Scale (LUNSERS) and a questionnaire including current height, weight, changes therein and smoking status.

AIMS

The aim of this study was to analyze weight and weight change in smoking and non-smoking patients taking clozapine. A possible interaction between obesity and smoking was explored.

RESULTS

No association was found between weight change and smoking status during clozapine treatment. There was no significant difference in body mass index (BMI) between non-smokers and smokers. In the analysis of covariance (ANCOVA) with BMI as the dependent variable, the best fitting model comprised age, sex, intensity of sedation, and reported amount of smoking as explanatory variables (ηp(2)= 0.116; P = 0.029; power = 0.750). None of the explanatory proportions of any single factor was significant.

CONCLUSIONS

Estimated according to reported weight gain and BMI, no difference was found between smoking and non-smoking clozapine-treated patients. Number of cigarettes smoked explained BMI if age and sex were taken into account. This result is in line with the findings of some general population studies, where heavy smoking has been associated with a greater risk of obesity.

Tobacco smoking and mental illness: important considerations

Tobacco smoking is a contributory factor in the death of 50% of individuals who are regular or heavy smokers (The Office of Tobacco Control Ireland defines a regular smoker as someone who smokes 11-20 per day and a heavy smoker as someone who smokes 21 or more cigarettes per day). The World Health Organisation (WHO) regards tobacco smoking as the leading preventable cause of death worldwide. In Ireland, approximately 750,000 people smoke tobacco regularly (23.5% of the population) with 7,000 Irish people dying annually from smoking-related causes. Although there are no exact figures for prevalence rates of smoking in individuals with mental illness in Ireland, international studies unequivocally state that the prevalence of smoking is significantly higher in those with mental illness, with greater nicotine intake and increased prevalence of nicotine dependence also reported. Furthermore people with mental illness experience greater withdrawal symptoms and have lower cessation rates when attempting to stop smoking compared to the general population.

The CYP1A2 -163C>A polymorphism is associated with clozapine-induced generalized tonic-clonic seizures in Brazilian schizophrenia patients

We evaluated two polymorphisms at CYP1A2 (*1C and *1F) in a sample of 108 European-derived patients with schizophrenia and their influence on the pro-convulsive effect of clozapine. We found the *1F/*1F genotype to be significantly associated with seizures, and no relationship was observed with combinations of *1F and *1C alleles.

Platelet antiaggregation therapy and subinguinal endovascular revascularization

BACKGROUND

Platelet antiaggregation therapy (PAT) is widely acknowledged to be a positive prognostic factor after revascularization, either at the coronary or the peripheral level. This study evaluated the results of infrainguinal endovascular procedures performed for critical ischemia, in accordance with patient compliance to clopidogrel treatment.

MATERIALS AND METHODS

This retrospective study included patients who underwent infrainguinal endovascular therapy for critical ischemia between January 2003 and December 2009. For 1 month, patients received the same postoperative PAT protocol: aspirin associated with clopidogrel, and then clopidogrel in the long term. Patient follow-up was set at 3 months, 6 months, 1 year, and then yearly thereafter. Survival rates, primary patency (PP), and limb salvage (LS) were studied in accordance with therapy compliance. Patients were classified into 2 groups: group 1 for compliant patients and group 2 for noncompliant patients in the long term. From January 2003 to December 2009, 153 infrainguinal endovascular procedures were performed on 150 patients experiencing critical ischemia who had benefited from the authors' postoperative PAT protocol.

RESULTS

Both groups were comparable in terms of comorbidity. Of the procedures performed in groups 1 (N = 105) and 2 (N = 45), 62.8% (n = 66) and 44.4% (n = 20), respectively, were femoral, 14.3% (n = 15) and 22.2% (n = 10), respectively, were infrapopliteal, and 22.9% (n = 24) and 33.4% (n = 15), respectively, were mixed. Mean follow-up time was 30.3 ± 20.2 months (range, 1-70 months). The survival rate was comparable between the groups (P = 0.46). PP and LS rates were significantly higher in group 1 than in group 2 (PP: 84% vs. 80%, respectively, at 1 year, 79% vs. 50%, respectively, at 2 years, 65% vs. 30%, respectively, at 3 years, and 60% vs. 18%, respectively, at 4 years; P = 0.02; LS: 92% vs. 78%, respectively, at 1 year, 86% vs. 62%, respectively, at 2 years, 80% vs. 55%, respectively, at 3 years, and 77% vs. 36%, respectively, at 4 years; P = 0.04).

CONCLUSIONS

This study shows that in common practice, 31% of patients stop their clopidogrel therapy, with a negative impact on PP and LS. These results indicate that medical follow-up after endovascular surgery must be reinforced.

Population pharmacokinetics of clozapine and its primary metabolite norclozapine in Chinese patients with schizophrenia

AIM

To develop a combined population pharmacokinetic model (PPK) to assess the magnitude and variability of exposure to both clozapine and its primary metabolite norclozapine in Chinese patients with refractory schizophrenia via sparse sampling with a focus on the effects of covariates on the pharmacokinetic parameters.

METHODS

Relevant patient concentration data (eg, demographic data, medication history, dosage regimen, time of last dose, sampling time, concentrations of clozapine and norclozapine, etc) were collected using a standardized data collection form. The demographic characteristics of the patients, including sex, age, weight, body surface area, smoking status, and information on concomitant medications as well as biochemical and hematological test results were recorded. Persons who had smoked 5 or more cigarettes per day within the last week were defined as smokers. The concentrations of clozapine and norclozapine were measured using a HPLC system equipped with a UV detector. PPK analysis was performed using NONMEM. Age, weight, sex, and smoking status were evaluated as main covariates. The model was internally validated using normalized prediction distribution errors.

RESULTS

A total of 809 clozapine concentration data sets and 808 norclozapine concentration data sets from 162 inpatients (74 males, 88 females) at multiple mental health sites in China were included. The one-compartment pharmacokinetic model with mixture error could best describe the concentration-time profiles of clozapine and norclozapine. The population-predicted clearance of clozapine and norclozapine in female nonsmokers were 21.9 and 32.7 L/h, respectively. The population-predicted volumes of distribution for clozapine and norclozapine were 526 and 624 L, respectively. Smoking was significantly associated with increases in the clearance (clozapine by 45%; norclozapine by 54.3%). The clearance was significantly greater in males than in females (clozapine by 20.8%; norclozapine by 24.2%). The clearance of clozapine and norclozapine did not differ significantly between Chinese patients and American patients.

CONCLUSION

Smoking and male were significantly associated with a lower exposure to clozapine and norclozapine due to higher clearance. This model can be used in individualized drug dosing and therapeutic drug monitoring.

A Kinetic Model for Simultaneous Fit of Clozapine and Norclozapine Concentrations in Chronic Schizophrenic Patients during Long-Term Treatment

OBJECTIVE

The pharmacokinetic profiles of clozapine and its main metabolite, norclozapine, were investigated in 18 chronic schizophrenic inpatients during long-term treatment.

PATIENTS

Patients received stable daily doses (between 300 and 900mg) for at least 1 month. Plasma drug concentrations were determined by high performance liquid chromatography. The pharmacokinetic parameters were calculated from both noncompartmental and compartmental approaches with zero-order input rate using a kinetic model for simultaneous fit of clozapine and norclozapine (active metabolite) concentrations.

RESULTS

Large interpatient variations in pharmacokinetic parameters of the two drugs were observed. Plasma clozapine concentration peaked on average at 2 hours. The mean elimination rate constants from compartments 1 (k(10)) and 2 (k(20 ), elimination rate constant of norclozapine) were 0.087 and 0.156h(-1), respectively. The rate of formation of norclozapine, k(12), averaged 1.25h(-1). The mean fraction of the administered dose converted to norclozapine was estimated to be 66%. The apparent clearance of clozapine (CL/F) averaged 44.7 L/h and the volume of distribution (V(c)/F) was 7.00 L/kg. The pharmacokinetics of clozapine after multiple doses were linear over the range of clozapine plasma concentrations of 145 to 1411 microg/L.

CONCLUSION

This is the first study assessing the pharmacokinetic profile of clozapine plus norclozapine in plasma during long-term treatment. This pharmacokinetic model can be used to determine the population pharmacokinetic parameters of clozapine and norclozapine in order to optimise individual dosage regimens using a Bayesian methodology.

Sex-dependent modulation of treatment response

The response to a psychotropic medication reflects characteristics of both the medication and the substrate, ie, the individual receiving the medication. Sex is an individual characteristic that influences all elements of the pharmacokinetic process - absorption, distribution, metabolism, and elimination. The effects of sex on these components of the pharmacokinetic process often counterbalance one another to yield minimal or varying sexual differences in blood levels achieved. However, sex also appears to influence pharmacodynamics, the tissue response to a given level of medication. Consideration by the practitioner of sex as a possible contributing factor to treatment nonresponse will enhance the efficacy and precision of clinical interventions.

Cigarette smoking, coffee drinking, and ingestion of charcoal-broiled beef as potential modifiers of drug therapy and confounders of clinical trials

A pathway of research is described, leading from the finding of an inhibitory effect of 3-methylcholanthrene on the carcinogenicity of an aminoazo dye, to the induction of drug-metabolizing enzymes by 3-methylcholanthrene, benzo[a]pyrene, and other polycyclic aromatic hydrocarbons, to the demonstration of enhanced drug metabolism in cigarette smokers, coffee drinkers, and people who eat charcoal-broiled beef. The results of these studies indicate that cigarette smoking, coffee drinking, and the ingestion of charcoal-broiled beef (all resulting in exposure to polycyclic aromatic hydrocarbons) can influence the dosing regimen needed for proper drug therapy and are potential confounders of clinical trials with drugs metabolized by polycyclic aromatic hydrocarbon-inducible enzymes.

Age and sex impact clozapine plasma concentrations in inpatients and outpatients with schizophrenia

BACKGROUND

Although clozapine is primarily used in a younger to mid-life population of patients with psychosis, there are limited data on the clinical pharmacology of clozapine later in life. The objective of this study was to assess the magnitude and variability of plasma concentrations of clozapine and norclozapine across the lifespan in a real-world clinical setting.

DESIGN

A population pharmacokinetic study using nonlinear mixed effect modeling (NONMEM). Age, sex, height, weight, and dosage formulation were covariates.

SETTING

Inpatients and outpatients at the Centre for Addiction and Mental Health, Toronto, from 2001 to 2007.

PARTICIPANTS

Patients ranging in ages from 11 to 79 with schizophrenia spectrum disorders and prescribed clozapine (Clozaril).

MEASUREMENTS

A total of 1142 plasma clozapine and norclozapine concentrations (2,284 concentration measurements) from 391 patients with schizophrenia spectrum disorder.

RESULTS

A one-compartment model with first-order absorption and elimination best described the data. The population predicted clearance of clozapine for females was 27.1 L/h (SE 11.1%) and 36.7 L/h (SE 9.7%) for males. For norclozapine, clearance in females was 48.6 L/h (SE 10.8%) and 63.1 L/h (SE 9.3%) in males. The only covariates with a significant effect on clearance were age and sex: clearance for both parent and metabolite decreased exponentially with age at least 39 years.

CONCLUSIONS

Decreased clearance of clozapine and norclozapine with age results in increased blood concentrations and, hence, the potential for adverse drug reactions. These findings have particular clinical relevance for the dosing and safety monitoring of clozapine in older adults, highlighting a need for increased vigilance.

Second-generation antipsychotic long-acting injections: systematic review

BACKGROUND

Second-generation antipsychotics (SGAs) represent an advance in the long-term management of schizophrenia.

AIMS

To review the available evidence concerning SGA long-acting injections (LAIs).

METHOD

A systematic review of the literature was conducted using PubMed.

RESULTS

Risperidone long-acting injection was the first licensed SGA-LAI compound and is effective in the long-term management of schizophrenia, with a safety profile similar to that of oral risperidone. Olanzapine pamoate has recently been approved in Europe. In terms of efficacy, at injection intervals of up to 4 weeks it appears comparable to oral olanzapine, although the potential for ;post-injection syndrome' (delirium) calls for additional safety considerations. Paliperidone palmitate is currently under review with the licensing authorities. It also affords the potential advantage of monthly dosing.

CONCLUSIONS

More long-term comparisons of SGA-LAIs with oral SGAs as well as with first-generation antipsychotic LAIs are needed. These studies should include cost-effectiveness data.

Impact of smoking cessation on psychiatric inpatients treated with clozapine or olanzapine

INTRODUCTION

The prevalence of smoking is high in persons with serious mental illness (SMI) despite associated health risks. Persons with SMI die on average 25 years earlier than the general population and an increased focus on wellness, including smoking cessation, has been a goal of federal, state, and municipal governments.

OBJECTIVES

The primary objective of this study was to evaluate the effects of smoking cessation on symptom severity in psychiatric inpatients at a New York State psychiatric facility 1 year after a smoke-free policy had been implemented. The secondary objective of this study was to evaluate cardiometabolic risk factors.

METHODS

A retrospective chart review of 26 adult psychiatric inpatients receiving either clozapine, olanzapine, or both at any time between January 2006 and December 2007 was conducted. In addition to Brief Psychiatric Rating Scale (BPRS) scores and cardiometabolic measures (body weight, body mass index [BMI], and blood pressures before and after implementation of the smoke-free policy), other information collected included age, gender, diagnosis, the frequency of psychiatric medications used on an as-needed (p.r.n.) basis, immediate-need (stat) medication use, medication dosing, number of psychiatric emergencies, Global Assessment of Functioning (GAF) scores, privilege status, and time in special observation. Patients were compared on their own pre- and post-smoking cessation parameters and data were analyzed using a dependent t-test with p < 0.01 chosen as indicating significance.

RESULTS

Data analysis revealed a small but statistically significant decrease in GAF scores (p < 0.01), but no other significant difference between values pre- and post-smoking cessation.

CONCLUSION

Analysis demonstrated no change in psychiatric symptomatology or cardiometabolic factors 1 year post-smoking cessation in individuals with schizophrenia taking clozapine, olanzapine, or both. Further investigation is needed before concluding that smoking cessation has no impact on symptoms or on cardiometabolic risk factors. Despite a slight but statistically significant worsening in GAF scores, the health benefits of smoking cessation should continue to form the basis of encouraging smoking cessation in persons with SMI while longer term and methodologically more rigorous assessments on psychiatric and general health status are undertaken.

Sensitivity to antipsychotic drugs in older adults

Antipsychotic medications are widely used to manage psychotic and behavioral disorders in older adults, including primary psychotic disorders such as schizophrenia, and psychosis and behavioral disturbances associated with dementia. These two broad diagnostic indications are associated with contrasting recommended treatment durations, with the former requiring indefinite treatment across the life span. Antipsychotic drug dosing for schizophrenia is based primarily on studies of younger patients and thus may not apply to older adults. It is critically important to address the effects of aging on antipsychotic dosing given the recent emergence of data that suggest a critical role for age-related sensitivity to these drugs. Antipsychotic drugs are not only associated with somatic and neurological adverse effects but also increased all-cause mortality and sudden cardiac death in this vulnerable population. This review focuses on the sensitivity of older adults to adverse effects from antipsychotic medications and the current pharmacokinetic and pharmacodynamic explanatory models of susceptibility. Implications of recent research findings for individualized pharmacotherapy are discussed.

Clozapine exposure and the impact of smoking and gender: a population pharmacokinetic study

The primary objective of this study was to evaluate the magnitude and variability of concentration exposure to clozapine and norclozapine in a real-world clinical setting, with a focus on smoking status, using population pharmacokinetic methodologies. A retrospective review of plasma clozapine and norclozapine concentrations taken from inpatients at the Centre for Addiction and Mental Health, Toronto, from 2001 to 2007 was conducted. A nonlinear mixed-effects model was developed using NONMEM, including age, gender, weight, smoking status, and dosage formulation as covariates. Pharmacokinetic parameters and interindividual and residual variabilities were estimated with 1- and 2-compartment models. A total of 519 plasma clozapine concentrations from 197 patients (138 males; mean +/- SD age, 38 +/- 13 years; schizophrenia spectrum disorder 98.2%) were included for the analysis. A 1-compartment model with first-order absorption and elimination best described the data. Apparent volume of distribution was fixed to a previously reported value in the literature of 7 L/kg.The population-predicted oral clearance of clozapine and norclozapine was 18.0 and 39.0 L/h, respectively; both the predicted clearance values vary nearly 6-fold (range, 9.18-59.06 and 16.29-97.84 L/h, respectively). For clozapine, smokers and males showed increased oral clearance by 6.0 and 4.5 L/h, respectively. For norclozapine, smokers and male gender were associated with an increased oral clearance of 11.3 and 7.6 L/h, respectively. The formulation of clozapine administered had an impact on the absorption rate with a Ka of 0.14/h for tablet and 10.3/h for the suspension form.The data suggest that smoking and male gender are associated with lower exposure to clozapine and norclozapine due to the higher oral clearance. These findings may account for some of the variability in clozapine exposure and have important implications for individualized drug dosing and therapeutic drug monitoring.

Sex-specific differences in side effects of psychotropic drugs: genes or gender?

Sex differences observed in the adverse effects associated with psychotropic drugs have not been reported consistently in the literature. In this review, we discuss the current published data on sex differences observed in the occurrence, symptomatology and reporting of the adverse effects associated with psychotropic drug effects, and discuss their clinical relevance. We reviewed the published data up to April 2009 on sex differences in the side effects of antipsychotics, antidepressant and mood stabilizers, by systematically searching PubMed using combinations of search terms and retrieving relevant references specifically reporting on these issues. The majority of the data was retrieved from clinical studies where the main outcome parameters did not relate specifically to sex differences. In most instances, sex was associated with other factors influencing side effects such as age, disease and body weight. Sex-related differences were reported in the side effects associated with antipsychotic drug-induced weight gain and metabolic syndrome, symptoms of sexual dysfunction caused by antidepressants and antipsychotic drugs and cardiac arrhythmic side effects associated with antipsychotic drugs. Women might differ from men not only in incidence but also in the presentation of clinical symptoms associated with adverse psychotropic drug effects. Clinicians should be made aware of the differences reported in the literature regarding the symptomatology, severity and recognition of the adverse psychotropic drug effects found in men and women.