Potentially fatal outcomes associated with clozapine

A study of the pharmacokinetics of clozapine and its metabolites by the dynamics of its distribution in the oral fluid of healthy volunteers

Clozapine (CLZ) -related accidents or crimes are common in the world. Oral fluid drug detection is a convenient measure of dealing with things like that. There has not been any literature reported detailedly the representation rule of clozapine and its metabolites in oral fluid so far. The study aimed to describe the pharmacokinetics of CLZ and its metabolites N-desmethylclozapine and clozapine-N-oxide in human oral fluid after a single 12.5 mg oral dose of CLZ. Twenty-nine volunteers, including 20 males and 9 females, were recruited, and 2 mL oral fluid was collected from each participant at post-consumption time-points of prior (zero), 0.5, 1.5, 3, 5, 8, 12, 24, 36, 51, 82, and 130 h, respectively. Analytes of interest were extracted with solid-phase extraction and analyzed with liquid chromatography tandem mass spectrometry method. Pharmacokinetic parameters were calculated using the pharmacokinetic software DAS according to the non-compartment model. The maximum concentration, the time of maximum concentration, oral clearance, and the elimination half-life of clozapine were 16.57 ± 9.63 ng/mL, 4.53 ± 3.61 h, 57.65 ± 23.77 L/h and 53.58 ± 52.28 h, respectively. The maximum concentration, the time of maximum concentration, and the elimination half-life of the metabolite N-desmethylclozapine were 3.08 ± 1.19 ng/mL, 9.38 ± 9.33 h and 62.67 ± 82.57 h, respectively; of clozapine-N-oxide were 1.15 ± 0.36 ng/mL, 4.53 ± 2.19 h and 19.15 ± 23.11 h, respectively. It was the first study on the pharmacokinetics of CLZ and its metabolites in the oral fluid of Chinese healthy volunteers, and it provided a basis for the therapeutic drug monitoring and toxicological interpretation in clozapine-related cases.

Evidence for the Role of the Mitochondrial ABC Transporter MDL1 in the Uptake of Clozapine and Related Molecules into the Yeast Saccharomyces cerevisiae

Clozapine is an antipsychotic drug whose accumulation in white cells can sometimes prove toxic; understanding the transporters and alleles responsible is thus highly desirable. We used a strategy in which a yeast (Saccharomyces cerevisiae) CRISPR-Cas9 knock-out library was exposed to cytotoxic concentrations of clozapine to determine those transporters whose absence made it more resistant; we also recognised the structural similarity of the fluorescent dye safranin O (also known as safranin T) to clozapine, allowing it to be used as a surrogate marker. Strains lacking the mitochondrial ABC transporter MDL1 (encoded by YLR188W) showed substantial resistance to clozapine. MDL1 overexpression also conferred extra sensitivity to clozapine and admitted a massive increase in the cellular and mitochondrial uptake of safranin O, as determined using flow cytometry and microscopically. Yeast lacking mitochondria showed no such unusual accumulation. Mitochondrial MDL1 is thus the main means of accumulation of clozapine in S. cerevisiae. The closest human homologue of S. cerevisiae MDL1 is ABCB10.

Evaluation of Global Dystonia Rating Scale as a predictor of unfavorable outcomes among acute antipsychotics poisoned patients

Worldwide, acute antipsychotic poisoning results in high morbidities and mortalities. Though extrapyramidal syndromes are commonly associated, the extent of extrapyramidal syndromes in relation to the severity of antipsychotic poisoning has not been addressed yet. Thus, this study aimed to assess the Global Dystonia Rating Scale (GDRS) as an unfavorable outcomes predictive tool in acute antipsychotic poisoning. A cross-sectional study included 506 antipsychotic-poisoned patients admitted to Tanta University Poison Control Center, Egypt, over three years was conducted. The mean GDRS was 9.1 ± 16.7 in typical antipsychotic poisoning, which was significantly higher than that of atypical antipsychotics (4.2 ± 11.5) (p = 0.003). Patients with GDRS> 20 showed significantly higher liability for all adverse outcomes (p < 0.05). However, poisoning with typical antipsychotics was associated with significantly more cardiotoxicity (p = 0.042), particularly prolonged QRS (p = 0.005), and intensive care unit (ICU) admission (p = 0.000). In contrary to the PSS, which failed to predict the studied adverse outcomes, GDRS significantly predicted all adverse outcomes (p < 0.000) for all antipsychotic generations. In atypical antipsychotics, GDRS above three accurately predicted cardiotoxicities, prolonged QTc interval, and respiratory failure with Area under curves (AUC) of 0.937, 0.963, and 0.941, respectively. In typical antipsychotic poisoning, at higher cutoffs (7.5, 27.5, 18, and 7.5), cardiotoxicities, prolonged QTc interval, and respiratory failure were accurately predicted (AUC were 0.974, 0.961, and 0.960, respectively). GDRS is an objective, substantially useful tool that quantifies dystonia and can be used as an early reliable predictor of potential toxicity in acute antipsychotic poisoning.

Association between initial clozapine titration and pneumonia risk among patients with schizophrenia in a Korean tertiary hospital

Pneumonia is a significant adverse drug reaction (ADR) associated with clozapine, characterized by high mortality and potential linkage with other inflammatory responses. Despite the critical nature, research regarding the development of pneumonia during initial clozapine titration remains limited. This retrospective study included 1408 Korean inpatients with schizophrenia spectrum disorders. Data were collected from January 2000 to January 2023. Pneumonia developed in 3.5 % of patients within 8 weeks of clozapine initiation. Patients who developed pneumonia were taking a greater number and higher dose of antipsychotics at baseline (2.14 vs. 1.58, p < 0.001; 25.64 vs. 19.34, p = 0.012). The average onset occurred 17.24 days after initiation, on an average dose of 151.28 mg/day. Titration was either paused or slowed in most of these patients, with no reported fatalities. The types of pneumonia included aspiration pneumonia, mycoplasma pneumonia, bronchopneumonia, and COVID-19 pneumonia. Myocarditis, drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome, and urinary tract infections were also identified. Logistic regression analysis revealed that a greater number of concomitant antipsychotics (odds ratio [OR] = 1.59, p = 0.027) and concomitant benzodiazepine use (OR = 2.33, p = 0.005) at baseline were associated with an increased risk of pneumonia. Overall, pneumonia development during clozapine titration is linked with other inflammatory ADRs, suggesting a shared immunological mechanism. Close monitoring is recommended, especially for patients taking multiple antipsychotics and benzodiazepines. Further studies involving repeated measures of clozapine concentrations at trough and steady state, along with a more detailed description of pneumonia types, are warranted.

Inflammatory markers in outpatients with schizophrenia diagnosis in regular use of clozapine: a cross-sectional study

It is known that inflammation worsen the course of schizophrenia and induce high clozapine serum levels. However, no study evaluated this change in function of clozapine daily dose in schizophrenia. We assessed the correlation between inflammation and severity symptoms in patients with schizophrenia that take and do not take clozapine. We also assessed the correlation between clozapine daily dose and inflammatory markers to patients who take this drug. Patients were recruited from Schizophrenia Ambulatory and Psychosocial Care Center of Clinical Hospital of Porto Alegre and from an association of relatives of patients with schizophrenia. Exam results, and other important clinical exam were assessed in patients record or patients were asked to show their exam in the case of outpatients. We included 104 patients, 90 clozapine users and 14 non-clozapine users. We calculate the systemic inflammatory markers [neutrophil-lymphocyte ratio (NLR), systemic immune inflammation index (SII), and the psychopathology severity by the Brief Psychiatric Rating Scaled anchored (BPRS-a)]. These variables were compared between clozapine users and non-clozapine users. It was used mean/median test according to data distributing, with study factor (SII, MLR, and PLR), the clinical outcome: severity of symptomatology (BPRS score), and clozapine daily dose as adjustment factor. Clozapine users exhibited a significantly higher neutrophil count (mean ± SD: 5.03 ± 2.07) compared to non-clozapine users (mean ± SD: 3.48 ± 1.27; p = 0.031). After controlling for comorbidity, other parameters also showed significant differences. These findings are consistent with previous studies that have demonstrated an inflammatory response following the administration of clozapine.

Inflammatory markers in outpatients with schizophrenia diagnosis in regular use of clozapine: a cross-sectional study

It is known that inflammation worsen the course of schizophrenia and induce high clozapine serum levels. However, no study evaluated this change in function of clozapine daily dose in schizophrenia. We assessed the correlation between inflammation and severity symptoms in patients with schizophrenia that take and do not take clozapine. We also assessed the correlation between clozapine daily dose and inflammatory markers to patients who take this drug. Patients were recruited from Schizophrenia Ambulatory and Psychosocial Care Center of Clinical Hospital of Porto Alegre and from an association of relatives of patients with schizophrenia. Exam results, and other important clinical exam were assessed in patients record or patients were asked to show their exam in the case of outpatients. We included 104 patients, 90 clozapine users and 14 non-clozapine users. We calculate the systemic inflammatory markers [neutrophil-lymphocyte ratio (NLR), systemic immune inflammation index (SII), and the psychopathology severity by the Brief Psychiatric Rating Scaled anchored (BPRS-a)]. These variables were compared between clozapine users and non-clozapine users. It was used mean/median test according to data distributing, with study factor (SII, MLR, and PLR), the clinical outcome: severity of symptomatology (BPRS score), and clozapine daily dose as adjustment factor. Clozapine users exhibited a significantly higher neutrophil count (mean ± SD: 5.03 ± 2.07) compared to non-clozapine users (mean ± SD: 3.48 ± 1.27; p = 0.031). After controlling for comorbidity, other parameters also showed significant differences. These findings are consistent with previous studies that have demonstrated an inflammatory response following the administration of clozapine.

The Therapeutic Potential of Carnosine as an Antidote against Drug-Induced Cardiotoxicity and Neurotoxicity: Focus on Nrf2 Pathway

Different drug classes such as antineoplastic drugs (anthracyclines, cyclophosphamide, 5-fluorouracil, taxanes, tyrosine kinase inhibitors), antiretroviral drugs, antipsychotic, and immunosuppressant drugs are known to induce cardiotoxic and neurotoxic effects. Recent studies have demonstrated that the impairment of the nuclear factor erythroid 2–related factor 2 (Nrf2) pathway is a primary event in the pathophysiology of drug-induced cardiotoxicity and neurotoxicity. The Nrf2 pathway regulates the expression of different genes whose products are involved in antioxidant and inflammatory responses and the detoxification of toxic species. Cardiotoxic drugs, such as the anthracycline doxorubicin, or neurotoxic drugs, such as paclitaxel, suppress or impair the Nrf2 pathway, whereas the rescue of this pathway counteracts both the oxidative stress and inflammation that are related to drug-induced cardiotoxicity and neurotoxicity. Therefore Nrf2 represents a novel pharmacological target to develop new antidotes in the field of clinical toxicology. Interestingly, carnosine (β-alanyl-l-histidine), an endogenous dipeptide that is characterized by strong antioxidant, anti-inflammatory, and neuroprotective properties is able to rescue/activate the Nrf2 pathway, as demonstrated by different preclinical studies and preliminary clinical evidence. Starting from these new data, in the present review, we examined the evidence on the therapeutic potential of carnosine as an endogenous antidote that is able to rescue the Nrf2 pathway and then counteract drug-induced cardiotoxicity and neurotoxicity.

Clozapine-Related Thromboembolic Events

Clozapine is an atypical antipsychotic used for treatment-resistant schizophrenia. Venous thromboembolism (VTE) is a rare side effect of clozapine which can be fatal. This article summarizes current evidence regarding the risk of VTE associated with the use of clozapine. We performed a PubMed (MeSH) and Google Scholar search for the last two decades. Studies or case reports performed in humans were included in the review, of which 42 case reports of patients taking clozapine at VTE onset were included in the analysis of this review. According to the articles reviewed, the mean age was 42.9 years, with more males (71.43%) than females (28.57%). The average clozapine dose was 285.62 mg/day. VTE onset occurred within the first six months in 71.8% of the cases. Overall, 70.37% of the patients had comorbidities, and 87.5% had risk factors for VTE. In total, 68.57% were prescribed other medications at VTE onset, and 60% were being treated with another antipsychotic concomitantly. Finally, 32.5% of the patients died, while 67.5% survived. In 60% of the cases, clozapine was discontinued after VTE. In our literature review, we observed that among clozapine users, VTE occurred at a wide dose range, and most of the events occurred within the first six months. As many patients who are prescribed clozapine have risk factors for VTE, the risk should be considered at the time of prescribing. Further research should be conducted to elucidate the risk of VTE in clozapine users and the benefits of thromboprophylaxis.

Clozapine-Induced Constipation: A Case Report and Review of Current Management Guidelines

Clozapine is a second-generation antipsychotic recommended after the failure of two or more antipsychotics for treatment-resistant schizophrenia. Clozapine proved to also decrease recurrent suicidal behaviors in schizophrenia spectrum disorders. Yet, physicians often use clozapine as a last resort despite its proven efficacy due to its side effect profile. A noted side effect of clozapine is agranulocytosis, which requires a weekly complete blood count with differentials. Clozapine's anticholinergic activity causes colonic hypomotility, leading to constipation, and only a few studies examined clozapine-induced constipation (CIC). Few of the reported complications of CIC include bowel obstruction or bowel perforation due to fecal impaction. Herein we document a case report of CIC and also conducted a review of published case reports examining the complexity and management of CIC. CIC is a critical condition if unresolved as it can lead to mortality. Future directions and guidelines should be developed for early diagnosis and treatment for CIC, which will provide reassurance and directions for both the physicians and patients.

Implementation and Outcomes of a Clozapine-Associated Myocarditis Screening Program in a Region of South Australia-Lessons Learned

PURPOSE

Clozapine-associated myocarditis (CAM) is a serious complication, mostly occurring in the first month of treatment. Public mental health in South Australia introduced a screening protocol in 2011 using baseline and weekly C-reactive protein and troponin. The aim of this study was to assess protocol adherence and management of cases with positive screening results.

METHODS

We identified all patients commenced on clozapine in our area between 2012 and 2015. Those with abnormal C-reactive protein and/or troponin in the first 4 weeks of treatment were identified (potential cases). For those, we collected clinical characteristics and test results and reviewed their management.

FINDINGS

Protocol compliance increased to 80%. We identified 24 potential CAM cases, 8 at high risk based on established definition (7.6% of new commencements) and 9 formally diagnosed from 143 commenced on clozapine. Potential cases not meeting CAM definition were significantly more likely commenced on clozapine for the first time and have preexisting respiratory disease. Likely CAM cases were younger, and more often prescribed additional antipsychotics, specifically quetiapine. Seven (78%) of 9 patients diagnosed with CAM met published CAM definition. In 14 undiagnosed potential cases, 10 (71%) did not have timely testing to exclude CAM.

CONCLUSIONS

Maintaining a high index of suspicion, clinical monitoring and timely testing is important to supplement CAM screening protocols. More research is needed to identify those that can be safely rechallenged or even continue clozapine treatment with monitoring.

Clozapine in the treatment of refractory schizophrenia: a practical guide for healthcare professionals

BACKGROUND

Clozapine remains the only medication licensed for treating refractory schizophrenia. However, it remains underutilized in part due to concerns regarding adverse events.

SOURCES OF DATA

Published literature.

AREAS OF AGREEMENT

Common adverse events during clozapine treatment include sedation, hypersalivation, postural hypotension, dysphagia, gastrointestinal hypomotility, weight gain, diabetes mellitus and dyslipidaemia. Rare but serious events include agranulocytosis, cardiomyopathy, myocarditis, pneumonia, paralytic ileus and seizure.

AREAS OF CONTROVERSY

It remains unclear how best to minimize clozapine-induced morbidity/mortality (i) during dose titration, (ii) from hypersalivation and (iii) from gastrointestinal hypomotility. It is also unclear how clozapine pharmacokinetics are affected by (i) gastrointestinal hypomotility, (ii) systemic infection and (iii) passive exposure to cigarette smoke. Whether monthly haematological monitoring needs to continue after 12 months of uninterrupted therapy is also a subject of debate.

GROWING POINTS

There is a need for better management of serious clozapine-related adverse events in addition to agranulocytosis. There is also a need for better education of patients and carers, general practitioners, A&E and ITU staff and others of the problems posed in using clozapine safely.

AREAS TIMELY FOR DEVELOPING RESEARCH

There is a need for more research on assessing clozapine dosage (i) as patients get older, (ii) with respect to exposure to cigarette smoke and (iii) optimizing response if adverse events or other factors limit dosage.

Protocol for Clozapine Rechallenge in a Case of Clozapine-Induced Myocarditis

OBJECTIVE

Protocol for clozapine rechallenge in patients with a history of clozapine-induced myocarditis.

METHOD

Clozapine-related cardiovascular adverse effects including myocarditis and cardiomyopathy have limited its widespread use in treatment-resistant schizophrenia. Here, we present a case of clozapine-induced myocarditis and successful cautious rechallenge. Ms. AA, a young female patient with severe psychosis developed myocarditis during her initial clozapine titration phase, which was thus discontinued. Subsequent response to other medications was poor, and she remained significantly disabled. We reviewed blood-based biomarkers identified during the emergence of her index episode of myocarditis and developed a successful clozapine rechallenge protocol, based on careful monitoring of changes in these indices and a very slow clozapine re-titration.

RESULTS AND CONCLUSIONS

This protocol may have utility in the management of patients with a history of clozapine-induced myocarditis.

Clozapine prescription pattern in patients with schizophrenia in Asia: The REAP survey (2016)

Clozapine is an effective antipsychotic medication for treatment resistant schizophrenia and is widely used in Asian countries. This study investigated clozapine prescription patterns and their associated factors in Asian countries and territories based on the database of the Research on Asian Psychotropic prescription study (REAP) conducted in 2016. Demographic and clinical information of 3744 schizophrenia patients in 15 Asian countries and territories was collected with a standardized data collection form. In total, 18.4% of the sample received clozapine, ranging from 2.6% in Japan to 32.3% in Hong Kong. Binary logistic regression analysis revealed that higher antipsychotic dose (OR = 1.002, P < 0.001), less frequent first admission in the sample (OR = 0.6, P < 0.001), more severe negative symptoms (OR = 1.4, P = 0.001) and less first generation antipsychotics (FGAs) (OR = 0.2, P < 0.001) were independently and significantly associated with clozapine prescription. Clozapine is frequently and increasingly prescribed for schizophrenia in Asia, with large variation across countries and territories. Given the diverse prescription patterns of clozapine found in Asian countries/territories, the clinical rationale of clozapine prescription needs careful consideration in Asia with more local input.

A comparative study of detection of myocarditis induced by clozapine: With and without cardiac monitoring

The aim of this study was to investigate and compare the incidence of suspected or definite cases of clozapine induced myocarditis (SDM) and clinical factors which could influence its onset in two different time periods, defined by pre- and post-cardiac monitoring at an inpatient setting, during the initiation phase of clozapine treatment. Hospital records of patients started on clozapine in the inpatient unit between 2011 and 2018 were investigated. Eight in 38 patients (11.3%) were classified as SDM after the initiation of the monitoring protocol, whereas only 1 in 33 patients (1.4%) was classified as SDM, before. Monitored and non-monitored patient groups were similar with regard to demographic and clinical variables. Diagnosis of schizoaffective disorder and use of concominant lithium, valproic acid and atypical antipsychotics were higher in patients with SDM, while clozapine dose titration was similar compared to the rest of the patients. Cardiac monitoring seems to be the main factor leading to the increase in the detection of clozapine induced myocarditis (CIM). If not monitored, the outcome of CIM can be fatal without any warning signs and symptoms. Concominant use of mood stabilizers including valproic acid and lithium, are important risk factors for the development of CIM.

Treatment-Resistant Schizophrenia: Genetic and Neuroimaging Correlates

Schizophrenia is a severe neuropsychiatric disorder that affects approximately 0.5–1% of the population. Response to antipsychotic therapy is highly variable, and it is not currently possible to predict those patients who will or will not respond to antipsychotic medication. Furthermore, a high percentage of patients, approximately 30%, are classified as treatment-resistant (treatment-resistant schizophrenia; TRS). TRS is defined as a non-response to at least two trials of antipsychotic medication of adequate dose and duration. These patients are usually treated with clozapine, the only evidence-based pharmacotherapy for TRS. However, clozapine is associated with severe adverse events. For these reasons, there is an increasing interest to identify better targets for drug development of new compounds and to establish better biomarkers for existing medications. The ability of antipsychotics to improve psychotic symptoms is dependent on their antagonist and reverse agonist activities at different neuroreceptors, and some genetic association studies of TRS have focused on different pharmacodynamic factors. Some genetic studies have shown an association between antipsychotic response or TRS and neurodevelopment candidate genes, antipsychotic mechanisms of action (such as dopaminergic, serotonergic, GABAergic, and glutamatergic) or pharmacokinetic factors (i.e., differences in the cytochrome families). Moreover, there is a growing body of literature on the structural and functional neuroimaging research into TRS. Neuroimaging studies can help to uncover the underlying neurobiological reasons for such resistance and identify resistant patients earlier. Studies examining the neuropharmacological mechanisms of antipsychotics, including clozapine, can help to improve our knowledge of their action on the central nervous system, with further implications for the discovery of biomarkers and the development of new treatments. The identification of the underlying mechanisms of TRS is a major challenge for developing personalized medicine in the psychiatric field for schizophrenia treatment. The main goal of precision medicine is to use genetic and brain-imaging information to improve the safety, effectiveness, and health outcomes of patients via more efficiently targeted risk stratification, prevention, and tailored medication and treatment management approaches. The aim of this review is to summarize the state of art of pharmacogenetic, pharmacogenomic and neuroimaging studies in TRS.