Safety of antipsychotics for the treatment of schizophrenia: a focus on the adverse effects of clozapine

A Rational Use of Clozapine Based on Adverse Drug Reactions, Pharmacokinetics, and Clinical Pharmacopsychology

Using Richardson and Davidson's model and the sciences of pharmacokinetics and clinical pharmacopsychology, this article reviewed the: (1) poor life expectancy associated with treatment-resistant schizophrenia (TRS), which may be improved in patients who adhere to clozapine; (2) findings that clozapine is the best treatment for TRS (according to efficacy, effectiveness and well-being); and (3) potential for clozapine to cause vulnerabilities, including potentially lethal adverse drug reactions such as agranulocytosis, pneumonia, and myocarditis. Rational use requires: (1) modification of the clozapine package insert worldwide to include lower doses for Asians and to avoid the lethality associated with pneumonia, (2) the use of clozapine levels for personalizing dosing, and (3) the use of slow and personalized titration. This may make clozapine as safe as possible and contribute to increased life expectancy and well-being. In the absence of data on COVID-19 in clozapine patients, clozapine possibly impairs immunological mechanisms and may increase pneumonia risk in infected patients. Psychiatrists should call their clozapine patients and families and explain to them that if the patient develops fever or flu-like symptoms, the psychiatrist should be called and should consider halving the clozapine dose. If the patient is hospitalized with pneumonia, the treating physician needs to assess for symptoms of clozapine intoxication since halving the dose may not be enough for all patients; consider decreasing it to one-third or even stopping it. Once the signs of inflammation and fever have disappeared, the clozapine dose can be slowly increased to the prior dosage level.

The Effect of Liver and Kidney Disease on the Pharmacokinetics of Clozapine and Sildenafil: A Physiologically Based Pharmacokinetic Modeling

Background and Objectives

Physiologically based pharmacokinetic (PBPK) modeling permits clinical scientists to reduce practical constraints for clinical trials on patients with special diseases. In this study, simulations were carried out to validate the pharmacokinetic parameters of clozapine and sildenafil using Simcyp^® simulator in young male adults and compare the effect of renal or hepatic impairment on the pharmacokinetic parameters of clozapine and sildenafil. Also, the effect of age on pharmacokinetic parameters of both drugs was investigated in healthy population and in patients with renal and hepatic impairment.

Methods

A full PBPK model was built in the simulator for clozapine and sildenafil based on physicochemical properties and observed clinical results. The model used was Advanced, Dissolution, Absorption and Metabolism (ADAM) for both drugs.

Results

The PBPK model adequately predicted the pharmacokinetic parameters of clozapine and sildenafil for the healthy adult population. In the simulation results, the bioavailability of both drugs was remarkably raised in both renal and hepatic impairment in young and elderly populations.

Conclusion

PBPK modeling could be helpful in the investigation and comparison of the pharmacokinetics in populations with specific disease conditions.

Atypical antipsychotic clozapine binds fibrinogen and affects fibrin formation

Clozapine is an atypical antipsychotic used for the treatment of schizophrenia. The prescribed target daily doses may reach 900 mg. Literature studies report a connection between clozapine usage and thrombosis development. Our in vitro study aimed to provide insight into molecular bases of this observation, investigating clozapine binding to fibrinogen, the main plasma protein involved in hemostasis. Fibrinogen/clozapine interaction was confirmed by protein fluorescence quenching, with an affinity constant of 1.7 × 10⁵ M^-1. Direct interactions did not affect the structure of fibrinogen, nor fibrinogen melting temperature. Clozapine binding affected fibrin formation by reducing coagulation speed and thickness of fibrin fibers suggesting that in the presence of clozapine, fibrinogen may acquire thrombogenic characteristics. Although no difference in fibrin gel porosity was detected, other factors present in the blood may act synergistically with altered fibrin formation to modify fibrin clot, thus increasing the risk for development of thrombosis in patients on clozapine treatment. ORAC and HORAC assays showed that clozapine reduced free radical-induced oxidation of fibrinogen. All observed effects of clozapine on fibrinogen are dose-dependent, with the effect on fibrin formation being more pronounced.

ASP2905, a specific inhibitor of the potassium channel Kv12.2 encoded by the Kcnh3 gene, is psychoactive in mice

Schizophrenia is a major psychiatric disorder associated with positive and negative symptoms and cognitive impairments. In this study, we used animal models of behavior to evaluate the antipsychotic activity of ASP2905, a potent and selective inhibitor of the potassium channel Kv12.2 encoded by the Kcnh3/BEC1 gene. ASP2905 inhibited hyperlocomotion induced by methamphetamine and by phencyclidine. In contrast, ASP2905 did not affect spontaneous locomotion, suggesting that ASP2905 selectively inhibits abnormal behaviors induced by stimulants. Chronic infusion of ASP2905 significantly ameliorated phencyclidine-induced prolongation of immobility time in mice subjected to the forced swimming test. These findings suggest that ASP2905 potentially mitigates symptoms of schizophrenia, such as apathy. The antipsychotic clozapine also reversed phencyclidine-induced prolonged immobility, while risperidone and haloperidol had no effect. Assessment of the effects of ASP2905 on latent learning deficits in mice treated with phencyclidine as neonates subjected to the water-finding task showed that ASP2905 significantly ameliorated phencyclidine-induced prolongation of finding latency, which reflects latent learning performance. These findings suggest that ASP2905 potentially mitigates cognitive impairments caused by schizophrenia, such as attention deficits. In contrast, administration of clozapine did not ameliorate phencyclidine-induced prolongation of finding latency. Therefore, ASP2905 may alleviate the broad spectrum of symptoms of schizophrenia, including positive and negative symptoms and cognitive impairments, which is in contrast to currently available antipsychotics, which are generally only partially effective for ameliorating these symptoms.

Immunoendocrine Peripheral Effects Induced by Atypical Antipsychotics

Atypical antipsychotics (AAP) or second-generation antipsychotics are the clinical option for schizophrenia treatment during acute psychoses, but they are also indicated for maintenance during lifetime, even though they are being used for other psychiatric conditions in clinical practice such as affective disorders and autism spectrum disorder, among others. These drugs are differentiated from typical antipsychotics based on their clinical profile and are a better choice because they cause fewer side effects regarding extrapyramidal symptoms (EPS). Even though they provide clear therapeutic benefits, AAP induce peripheral effects that trigger phenotypic, functional, and systemic changes outside the Central Nervous System (CNS). Metabolic disease is frequently associated with AAP and significantly impacts the patient's quality of life. However, other peripheral changes of clinical relevance are present during AAP treatment, such as alterations in the immune and endocrine systems as well as the intestinal microbiome. These less studied alterations also have a significant impact in the patient's health status. This manuscript aims to revise the peripheral immunological, endocrine, and intestinal microbiome changes induced by AAP consumption recommended in the clinical guidelines for schizophrenia and other psychiatric disorders.

Use of cardiovascular and antidiabetic drugs before and after starting with clozapine versus other antipsychotic drugs: a Dutch database study

Reports of decreased mortality among patients with schizophrenia who use clozapine may be biased if clozapine is prescribed to relatively healthy patients and if intensive monitoring during its use prevents (under-treatment of) somatic disorder. We aimed to assess whether there is a difference in: (1) somatic comorbidity between patients who start with clozapine and those who start with other antipsychotics and (2) prescribed somatic medication, between patients using clozapine and those using olanzapine. Cohort study based on insurance claims (2010-2015). After selecting new users of antipsychotics and those who subsequently switched to clozapine (N = 158), aripiprazole (N = 295), olanzapine (N = 204) or first-generation antipsychotics (N = 295), we compared the clozapine starters to others on cardiovascular or diabetic comorbidity. Those using clozapine and olanzapine were compared on new prescriptions for cardiovascular or antidiabetic drugs. The ORadj of cardiovascular or diabetic comorbidity among other starters compared with clozapine starters was 0.77 [95% confidence interval (CI): 0.43-1.39], that is, a nonsignificantly increased prevalence associated with clozapine was found. Users of clozapine received significantly more new prescriptions for cardiovascular or antidiabetic medication (ORadj: 2.70, 95% CI: 1.43-5.08). Starters with clozapine were not cardiovascular/metabolic healthier than starters with other antipsychotics. During its use, they received more somatic treatment.

Rehospitalization Risk of Receptor-Affinity Profile in Antipsychotic Drug Treatment: A Propensity Score Matching Analysis Using a Japanese Employment-Based Health Insurance Database

PURPOSE

The aim of this study was to examine whether there is a difference in the risk of rehospitalization when antipsychotics are classified into two groups treated using drugs with a higher or lower affinity to H1 or α1 receptors than to D2 receptors (histamine H1 receptors, adrenaline α1 receptors [HA] high- and HA low-affinity drug group, respectively) based on affinity to receptors related to sedation using a nationwide insurance claims database in Japan.

PATIENTS AND METHODS

We identified eligible patients by the following two criteria: (i) hospitalization due to schizophrenia (International Classification of Disease [ICD]-10 code: F20 or F25) in psychiatric wards between January 1st, 2005 and August 31st, 2017, and (ii) administration of HA high- or HA low-affinity drugs in the next month after discharge from the earliest hospitalization due to schizophrenia (index month). The primary endpoint was rehospitalization due to schizophrenia. The secondary endpoints were (i) involuntary rehospitalization, (ii) concomitant use of anxiolytics/hypnotics, mood stabilizers, and antiparkinsonian drugs, (iii) all-cause death, and (iv) medication discontinuation. Propensity score (PS) matching analysis was applied, and the hazard ratio (HR) of the event rate in the HA high-affinity drug group relative to the HA low-affinity drug group was calculated using Cox's proportional hazards model.

RESULTS

Two thousand nine hundred and forty patients were identified as eligible patients. Among PS-matched patients (819 in each group), the HR in the HA high-affinity drug group compared with the HA low-affinity drug group was 1.018 (0.822-1.260, P = 0.870). Other outcomes did not differ significantly between the two groups.

CONCLUSION

No significant difference was observed in the rehospitalization risk due to schizophrenia associated with HA high-affinity antipsychotic drugs. Although this study was a retrospective PS-matched cohort study, the possibility of masking of the rehospitalization risk cannot be excluded because more than 80% of the patients were administered an anxiolytic/hypnotic at the time of admission.

Neuropeptides and oligopeptidases in schizophrenia

Schizophrenia (SCZ) is a complex psychiatric disorder with severe impact on patient's livelihood. In the last years, the importance of neuropeptides in SCZ and other CNS disorders has been recognized, mainly due to their ability to modulate the signaling of classical monoaminergic neurotransmitters as dopamine. In addition, a class of enzymes coined as oligopeptidases are able to cleave several of these neuropeptides, and their potential implication in SCZ was also demonstrated. Interestingly, these enzymes are able to play roles as modulators of neuropeptidergic systems, and they were also implicated in neurogenesis, neurite outgrowth, neuron migration, and therefore, in neurodevelopment and brain formation. Altered activity of oligopeptidases in SCZ was described only more recently, suggesting their possible utility as biomarkers for mental disorders diagnosis or treatment response. We provide here an updated and comprehensive review on neuropeptides and oligopeptidases involved in mental disorders, aiming to attract the attention of physicians to the potential of targeting this system for improving the therapy and for understanding the neurobiology underlying mental disorders as SCZ.

The Eminence of Co-Expressed Ties in Schizophrenia Network Communities

Exploring gene networks is crucial for identifying significant biological interactions occurring in a disease condition. These interactions can be acknowledged by modeling the tie structure of networks. Such tie orientations are often detected within embedded community structures. However, most of the prevailing community detection modules are intended to capture information from nodes and its attributes, usually ignoring the ties. In this study, a modularity maximization algorithm is proposed based on nonlinear representation of local tangent space alignment (LTSA). Initially, the tangent coordinates are computed locally to identify k-nearest neighbors across the genes. These local neighbors are further optimized by generating a nonlinear network embedding function for detecting gene communities based on eigenvector decomposition. Experimental results suggest that this algorithm detects gene modules with a better modularity index of 0.9256, compared to other traditional community detection algorithms. Furthermore, co-expressed genes across these communities are identified by discovering the characteristic tie structures. These detected ties are known to have substantial biological influence in the progression of schizophrenia, thereby signifying the influence of tie patterns in biological networks. This technique can be extended logically on other diseases networks for detecting substantial gene “hotspots”.

Prescription of antipsychotic and concomitant medications for adult Asian schizophrenia patients: Findings of the 2016 Research on Asian Psychotropic Prescription Patterns (REAP) survey

OBJECTIVE

Regular surveys are important to monitor the use of psychotropic medications in clinical practice. This study examined the psychotropic prescription patterns in adult Asian schizophrenia patients based on the data of the Research on Asian Psychotropic Prescription (REAP) 2016 survey.

METHODS

This cross-sectional survey across 15 Asian countries/territories collected socio-demographic and clinical data with standardized procedures between March and May 2016. The socio-demographic and clinical characteristics of the patients were recorded with a standardized questionnaire.

RESULTS

Altogether 3,537 adult patients with schizophrenia were consecutively screened and enrolled in the survey. The mean age was 38.66 ± 11.55 years and 59.7% of the sample were male. The mean dose of antipsychotics in chlorpromazine equivalents (CPZeq) was 424 ± 376 mg/day; 31.3% and 80.8% received first- and second- generation antipsychotics, respectively and 42.6% had antipsychotic polypharmacy, 11.7% had antidepressants, 13.7% had mood stabilizers, 27.8% had benzodiazepines, and 45.6% had anticholinergics.

CONCLUSIONS

Psychotropic prescription patterns in Asian adult patients with schizophrenia varied across countries. Regular surveys on psychotropic medications for schizophrenia are important to monitor pharmacotherapy practice in Asia.

Implementation of pharmacogenetics in a clozapine treatment resistant patient: a case report

We report the case of a young Caucasian male with disorganized chronic schizophrenia, an active smoker and nonresponder to 400 mg of clozapine/day. Therapeutic clozapine monitoring was analyzed revealing a low clozapine:norclozapine ratio. An additional pharmacogenetic test was carried out showing that the patient carried *1F variant ( CYP1A2 gene), which has been associated with nonresponse to clozapine in smoker patients. A genetic variation in the SLC6A4 gene was also found, which could be related to the poor response to clozapine. The remainder of the genes analyzed ( CYP2D6, ABCB1 and HTR2A) were not directly associated with the patient’s phenotype. The dose of clozapine was increased to 600 mg/day, reaching the therapeutic range. This case shows how pharmacogenetics can help in understanding the value of plasma levels to provide clinical improvement.

When clozapine appears at a dance event…

Objectives: The content of substances sold and consumed as party drugs is often unknown. They may contain inactive, contaminated or unexpected ingredients, and the dosage of the active components may vary considerably. Obviously, these phenomena increase the chances of a wrong or delayed therapy. To illustrate this point, we report 3 cases of clozapine intoxication at a dance event where most likely clozapine tablets were sold as party drugs.Methods: The three cases were part of a prospective toxicology study at a nocturnal indoor dance event.Results: One patient had to be intubated after obstructive breathing with desaturation and bradycardia, while the 2 other patients presented with syncope and altered mental status. All patients recovered after 20 minutes to 8 hours. Systematic toxicological analysis of the blood samples revealed the presence of clozapine (73-244 ng/ml) and its metabolite norclozapine (9-59 ng/ml). A pill, found in a pocket of one patient, was identified as Leponex® 100 mg (clozapine). This neuroleptic drug is mainly prescribed for treatment-resistant schizophrenia. In clozapine-naive subjects, orthostatic hypotension, bradycardia and syncope have been reported with a single 25 mg oral dose. Serum clozapine concentrations of the 3 cases were below the defined therapeutic range (350-600ng/ml) and the clozapine:norclozapine ratios were suggestive for recent drug intake.Conclusion: Routine drug screening may be unable to detect the toxic agent(s) involved. Whenever unusual symptoms are observed in an intoxicated patient, blood and urine samples should be sent to a reference toxicology laboratory.

Clozapine-Induced Cardiotoxicity Presenting as Sepsis: A Case Report and Literature Review

Clozapine is an atypical antipsychotic agent indicated in the treatment of medication-resistant schizophrenia. It is often reserved as a last line of treatment owing to the potential for serious and potentially life-threatening side effects, the most serious being agranulocytosis requiring close hematological monitoring and possible discontinuation of the medication from further use in the patient even when the agranulocytosis resolves. Other complications of clozapine include sedation, weight gain, elevated triglyceride levels, postural hypotension, and tachycardia. However, the potentially serious complication of myocarditis, though rare (with an incidence of 3%), may lead to cardiomyopathy as described in our present case. We present a 21-year-old patient who was started on clozapine for management of schizophrenia. He developed fever and tachycardia and was admitted to the medical unit on intravenous antibiotics for management of sepsis as he met the criteria for systemic inflammatory response syndrome. His labs revealed an elevated troponin and trending eosinophilia, which, in the context of clozapine use, raises the suspicion of clozapine cardiotoxicity. Echocardiogram showed reduced systolic function (45%). Clozapine was immediately discontinued, and his repeat echocardiogram showed normalization of his systolic function. In view of the increased prevalence of psychiatric illnesses, internists should be aware of rare but potentially life-threatening side effects.

Real-world effectiveness of antipsychotic monotherapy and polytherapy in 1543 patients with acute-phase schizophrenia

PURPOSE

The effectiveness of antipsychotic treatments in the acute phase of schizophrenia in actual clinical practice remains somewhat unclear. Therefore, the purpose of the present naturalistic, multi-center study conducted from 1 year starting in September 2017 was to examine the response rate to an initial or second antipsychotic in newly admitted patients with acute-phase schizophrenia, as well as the response rate and quality of augmentation with two antipsychotics in patients who failed to respond to both the initial and second antipsychotics.

RESULTS

In total, there were 660 (42.8%) and 243 (15.7%) responders to an initial and a second antipsychotic, respectively; thus, 58.5% of all patients were responders to an initial or second antipsychotic. Among 581 nonresponders (37.7%), the initial antipsychotic or a third antipsychotic was added to the second antipsychotic. Among these patients, 89.8% showed a Clinical Global Impression-Improvement score ≤3 (from 'minimally improved' to 'very much improved'). The rates of adverse events such as hyperglycemia, hyper-low-density lipoprotein cholesterolemia, hypertriglyceridemia, hyperprolactinemia, QTc prolongation, and extrapyramidal symptoms were not high in patients receiving augmentation with two antipsychotics compared with all patients, and no serious adverse events were reported.

CONCLUSION

Antipsychotic augmentation may be an option in acute-phase treatment for patients who do not respond to either an initial or a second antipsychotic.

A commentary on the efficacy of olanzapine for the treatment of schizophrenia: the past, present, and future

Olanzapine is a second-generation atypical antipsychotic with proven efficacy for the treatment of schizophrenia. Approved in 1996, olanzapine is one of the most studied antipsychotics, resulting in a considerable amount of clinical data across diverse patient populations. Despite the fact that olanzapine is associated with a known risk of metabolic side effects, including weight gain, many clinicians continue to prescribe olanzapine for the treatment of schizophrenia with the expectation of additional therapeutic antipsychotic efficacy relative to other first-line atypical antipsychotics. The goal of this narrative is to revisit the role of oral olanzapine in the management of patients with schizophrenia, including those with recently diagnosed schizophrenia ("first-episode"), those with an established schizophrenia diagnosis who experience acute exacerbations, those receiving long-term antipsychotic treatment as a maintenance intervention, and those with suboptimal response to antipsychotic treatment, including treatment resistance. Collectively, data from published literature support the favorable efficacy of olanzapine compared with other first- and second-generation antipsychotics, including lower rates of treatment discontinuation and clinically meaningful improvements in the symptoms of schizophrenia. The development of antipsychotic medications with the favorable efficacy of olanzapine, but with reduced weight gain, could address a major unmet need in the treatment of schizophrenia.

A qualitative exploration of clozapine prescribing and monitoring practices in the Arabian Gulf countries

Clozapine is considered as the first line antipsychotic for treatment resistant schizophrenia (TRS). Worldwide reports indicate an overall underutilization of clozapine in patients experiencing TRS. This study aims to understand the prescribing practices, monitoring strategies and barriers to the use of clozapine in the Arabian Gulf (AG) region. Qualitative methodology was employed to explore mental health professionals' experience with clozapine prescribing practices. Semi-structured, individual in-depth interviews were conducted. All interviews were analyzed using a thematic approach. A total of 13 interviews were conducted with participants from six AG countries. Four major themes emerged from the analysis in relation to clozapine prescribing and monitoring practices, clozapine use guidelines, and barriers to the use of clozapine. Thematic analysis revealed a tendency to under prescribe clozapine in the AG region, which appears to be predominantly influenced by prescriber-related barriers and less likely due to the lack of a nation-wide hematological monitoring program. Future studies should explore strategies for overcoming the barriers identified.

Current Concepts and Treatments of Schizophrenia

Schizophrenia is a debilitating mental illness which involves three groups of symptoms, i.e., positive, negative and cognitive, and has major public health implications. According to various sources, it affects up to 1% of the population. The pathomechanism of schizophrenia is not fully understood and current antipsychotics are characterized by severe limitations. Firstly, these treatments are efficient for about half of patients only. Secondly, they ameliorate mainly positive symptoms (e.g., hallucinations and thought disorders which are the core of the disease) but negative (e.g., flat affect and social withdrawal) and cognitive (e.g., learning and attention disorders) symptoms remain untreated. Thirdly, they involve severe neurological and metabolic side effects and may lead to sexual dysfunction or agranulocytosis (clozapine). It is generally agreed that the interactions of antipsychotics with various neurotransmitter receptors are responsible for their effects to treat schizophrenia symptoms. In particular, several G protein-coupled receptors (GPCRs), mainly dopamine, serotonin and adrenaline receptors, are traditional molecular targets for antipsychotics. Comprehensive research on GPCRs resulted in the exploration of novel important signaling mechanisms of GPCRs which are crucial for drug discovery: intentionally non-selective multi-target compounds, allosteric modulators, functionally selective compounds and receptor oligomerization. In this review, we cover current hypotheses of schizophrenia, involving different neurotransmitter systems, discuss available treatments and present novel concepts in schizophrenia and its treatment, involving mainly novel mechanisms of GPCRs signaling.