Exploring the potential effect of polypharmacy on the hematologic profiles of clozapine patients

Infections associated with clozapine: a pharmacovigilance study using VigiBase®

Introduction: Clozapine is primarily reserved for treatment-resistant schizophrenia due to safety concerns associated with its use. Infections have been reported with clozapine, which may lead to elevated serum levels of the drug. However, the existing literature on this topic is limited. Therefore, we conducted a study using VigiBase® to investigate the potential over-reporting of infections associated with clozapine, to explore the presence of dose-dependency, and to investigate the underlying mechanism. Methods: Disproportionality analyses were performed using VigiBase to assess the association between clozapine and all types of infections, the association between clozapine-associated infections and neutropenia, the association between clozapine-associated infections and agranulocytosis, the dose-effect relationship between clozapine and infections, and the interaction between clozapine and the main strong CYP450 inhibitors using reports carried out until 11 April 2023. Results: A statistically significant signal of infections was observed with clozapine, as indicated by an information component of 0.43 [95% CI: (0.41-0.45)]. The most commonly reported infections were respiratory and gastrointestinal in nature. Neutropenia showed weaker association with clozapine-associated reports of infections compared to other clozapine-associated reports [X2 (1, N = 204,073) = 454; p < 0.005], while agranulocytosis demonstrated a stronger association with clozapine-associated reports of infections [X2 (1, N = 204,073) = 56; p < 0.005]. No evidence of dose-dependency was observed. Among the 17 tested CYP inhibitors, significant drug-drug interactions were found with clarithromycin, metronidazole, valproic acid, lansoprazole, omeprazole, amiodarone, and esomeprazole. Discussion: Our study revealed a significant safety signal between clozapine use and infections, predominantly respiratory and gastrointestinal infections. The co-administration of clozapine with valproic acid or proton pump inhibitors may potentially contribute to an increased risk of infection. Further vigilance is warranted in clinical practice, and consideration of therapeutic drug monitoring of clozapine in cases involving concomitant use of these drugs or in the presence of infections may be beneficial.

Combination of strategies to initiate clozapine for refractory schizophrenia in a patient with low neutrophil levels

Clozapine is the only drug with confirmed efficacy for refractory schizophrenia; however, its use is restricted due to the risk of potentially life-threatening side effects, such as agranulocytosis. Although this restriction ensures safety against haematological risks, some patients with refractory schizophrenia who have low neutrophil levels may miss the opportunity to receive clozapine treatment. We herein report the case of a patient with refractory schizophrenia and low neutrophil levels who was successfully initiated on clozapine treatment after the use of several methods for increasing neutrophil levels. These strategies consisted of discontinuation of antipsychotics, treatment with lithium carbonate and adenine, and light exercise before blood testing. Combining these procedures may be an effective option in the treatment of patients with refractory schizophrenia whose neutrophil levels are not sufficient to initiate clozapine.

Recognition and management of clozapine adverse effects: A systematic review and qualitative synthesis

OBJECTIVE

Clozapine is substantially underutilized in most countries and clinician factors including lack of knowledge and concerns about adverse drug effects (ADEs) contribute strongly to treatment reluctance. The aim of this systematic review was to provide clinicians with a comprehensive information source regarding clozapine ADEs.

METHODS

PubMed and Embase databases were searched for English language reviews concerned with clozapine ADEs; publications identified by the automated search were manually searched for additional relevant citations. Following exclusion of redundant and irrelevant reports, pertinent information was summarized in evidence tables corresponding to each of six major ADE domains; two authors reviewed all citations for each ADE domain and summarized their content by consensus in the corresponding evidence table. This study was conducted in accordance with PRISMA principles.

RESULTS

Primary and secondary searches identified a total of 305 unique reports, of which 152 were included in the qualitative synthesis. Most clozapine ADEs emerge within 3 months, and almost all appear within 6 months, after initiation. Notable exceptions are weight gain, diabetic ketoacidosis (DKA), severe clozapine-induced gastrointestinal hypomotility (CIGH), clozapine-induced cardiomyopathy (CICM), seizures, and clozapine-induced neutropenia (CIN). Most clozapine ADEs subside gradually or respond to dose reduction; those that prompt discontinuation generally do not preclude rechallenge. Rechallenge is generally inadvisable for clozapine-induced myocarditis (CIM), CICM, and clozapine-induced agranulocytosis (CIA). Clozapine plasma levels >600-1000 μg/L appear more likely to cause certain ADEs (e.g., seizures) and, although there is no clear toxicity threshold, risk/benefit ratios are generally unfavorable above 1000 μg/L.

CONCLUSION

Clozapine ADEs rarely require discontinuation.

Never Say Never: Successful Clozapine Rechallenge After Multiple Episodes of Neutropenia

Clozapine is a second-generation antipsychotic with a superior efficacy for the management of treatment-resistant schizophrenia but underutilized because of potential side effects. A 59-year-old Caucasian male veteran was transferred from the long-term care unit to the acute psychiatry unit because of suicidality. He was noted as having a long-standing history of psychosis with significant referential and paranoid delusions. He had experienced two previous trials of clozapine; although he had significant response in the past, both trials ended in neutropenia and an absolute neutrophil count <500 cells per microliter, despite the second trial also including supplemental "as-needed" doses of pegfilgrastim to manage decline in neutrophil counts. This particular strategy of filgrastim use was determined to be a weakness of the second trial. A PubMed search identified recent literature that discussed preemptive dosing of filgrastim to prevent neutropenia. Thus, a protocol was established to administer 300 μg filgrastim subcutaneously, three times weekly, concurrently with clozapine initiation. This plan was discussed on local and national levels to achieve consensus before its initiation. Using a revised, patient-specific protocol led to successful initiation of clozapine and the ability to maintain the regimen for over 24 months without interruption or any further suicidal ideation.

Antipsychotic drugs and risk of newly diagnosed tuberculosis in schizophrenia

AIM

Patients with schizophrenia have a higher incidence of tuberculosis than do people in the general population. Information is limited regarding the association between antipsychotic agents and the risk of tuberculosis in patients with schizophrenia. This exploratory study assessed the risk of tuberculosis among patients with schizophrenia on antipsychotic therapy.

METHODS

Among a nationwide schizophrenia cohort derived from the National Health Insurance Research Database in Taiwan (n = 32 399), we identified 284 patients who had developed newly diagnosed tuberculosis after their first psychiatric admission. Ten or fewer matched controls were selected randomly from the cohort for each patient based on risk-set sampling. We categorized exposure to antipsychotic medications by type and defined daily dose. Using multivariate methods, we explored individual antipsychotic agents for the risk of tuberculosis and employed a propensity-scoring method in sensitivity analyses to validate any associations.

RESULTS

Among the antipsychotic agents studied and after adjustment for covariates, current use of clozapine was the only antipsychotic agent associated with a 63% increased risk of tuberculosis (adjusted risk ratio = 1.63, P = 0.014). In addition, the association did not show a clear dose-dependent relationship. Clozapine combined with other antipsychotic agents showed a potential synergistic risk for tuberculosis (adjusted risk ratio = 2.30, P = 0.044).

CONCLUSION

This exploratory study suggests the potential risk of clozapine on the risk of tuberculosis, especially for those on clozapine in combination with other antipsychotics. Future studies are needed to verify the association.

Increased risk for thionamide-induced agranulocytosis in elderly patients: a case presentation and literature review

Thionamides, such as methimazole and propylthiouracil, are used for the management of hyperthyroidism. Agranulocytosis is a rare adverse effect of thionamides and elderly patients are especially vulnerable. Here we discuss a case of an 80-year-old woman who developed agranulocytosis and pneumonia approximately 4 weeks after starting low dose methimazole therapy. Despite aggressive treatment with broad-spectrum antibiotics and granulocyte colony stimulating factor, she developed multiorgan failure and died. Our goals are to identify risk factors common to elderly patients and hopefully improve outcomes in this population when prescribed thionamides.

Potential Mechanisms of Hematological Adverse Drug Reactions in Patients Receiving Clozapine in Combination With Proton Pump Inhibitors

Clozapine is a second-generation antipsychotic which has proven efficacy in treating the symptoms of schizophrenia. Although clozapine therapy is associated with a number of adverse drug reactions, it is frequently used. One of the most common adverse drug reactions is gastroesophageal reflux disease which is an indication for treatment with proton pump inhibitors (PPIs). Coadministration of clozapine and PPIs increases the risk of hematological adverse drug reactions, including neutropenia and agranulocytosis. The mechanism in idiosyncratic agranulocytosis is not dose related and involves either a direct toxic or an immune-allergic effect. It is suspected that the clozapine metabolites nitrenium ion and N-desmethylclozapine may cause apoptosis or impair growth of granulocytes. Formation of N-desmethylclozapine is correlated with activity of the cytochrome P450 enzymes 1A2 and 3A4 (CYP1A2 and CYP3A4). Nitrenium ion is produced by the flavin-containing monooxygenase system of leukocytes. A drug interaction between clozapine and a PPI is a consequence of the induction of common metabolic pathways either by the PPI or clozapine. Findings to date suggest that indirect induction of flavin-containing monooxygenase by omeprazole through the aryl hydrocarbon receptor increases the expression of the enzyme mRNA and in the long term may cause the increase in activity. Moreover, induction of CYP1A2, especially by omeprazole and lansoprazole, may increase the serum concentration of N-desmethylclozapine, which can accumulate in lymphocytes and may achieve toxic levels. Another hypothesis that may explain hematological adverse drug reactions is competitive inhibition of CYP2C19, which may contribute to increased serum concentrations of toxic metabolites.

Effects of antipsychotics, antidepressants and mood stabilizers on risk for physical diseases in people with schizophrenia, depression and bipolar disorder

People with severe mental illness have a considerably shorter lifespan than the general population. This excess mortality is mainly due to physical illness. Next to mental illness-related factors, unhealthy lifestyle, and disparities in health care access and utilization, psychotropic medications can contribute to the risk of physical morbidity and mortality. We systematically reviewed the effects of antipsychotics, antidepressants and mood stabilizers on physical health outcomes in people with schizophrenia, depression and bipolar disorder. Updating and expanding our prior systematic review published in this journal, we searched MEDLINE (November 2009 - November 2014), combining the MeSH terms of major physical disease categories (and/or relevant diseases within these categories) with schizophrenia, major depressive disorder and bipolar disorder, and the three major psychotropic classes which received regulatory approval for these disorders, i.e., antipsychotics, antidepressants and mood stabilizers. We gave precedence to results from (systematic) reviews and meta-analyses wherever possible. Antipsychotics, and to a more restricted degree antidepressants and mood stabilizers, are associated with an increased risk for several physical diseases, including obesity, dyslipidemia, diabetes mellitus, thyroid disorders, hyponatremia; cardiovascular, respiratory tract, gastrointestinal, haematological, musculoskeletal and renal diseases, as well as movement and seizure disorders. Higher dosages, polypharmacy, and treatment of vulnerable (e.g., old or young) individuals are associated with greater absolute (elderly) and relative (youth) risk for most of these physical diseases. To what degree medication-specific and patient-specific risk factors interact, and how adverse outcomes can be minimized, allowing patients to derive maximum benefits from these medications, requires adequate clinical attention and further research.