Hepatitis, Interstitial Nephritis, and Pancreatitis in Association With Clozapine Treatment: A Systematic Review of Case Series and Reports

Overcoming clozapine's adverse events: a narrative review of systematic reviews and meta-analyses

INTRODUCTION

Clozapine is the gold standard treatment for treatment-resistant schizophrenia, however adverse events remain a clinical challenge.

AREAS COVERED

This review presents a narrative synthesis of systematic reviews and meta-analyses that have reported the onset, incidence, prevalence, and management of clozapine's adverse events. We conducted a systematic literature search using PubMed, Embase, PsycINFO, OvidMEDLINE, CINAHL, and the Cochrane Database of Systematic Reviews from inception to April 2024.

EXPERT OPINION

Effective management of clozapine's adverse events necessitates multi-faceted, individualized, and shared-decision strategies. Despite a lack of high-quality systematic evidence, expert inter-disciplinary solutions are provided to help address a critical need for clinical guidance. This 35-year update offers an evidence-based framework to assist clinicians, patients, and caregivers navigate the adverse events associated with clozapine therapy.

Evaluation of major adverse events of clozapine based on accordance to an international titration guideline

Introduction

Clozapine is the only antipsychotic approved for treatment-resistant schizophrenia, but without appropriate monitoring, it can be associated with potentially fatal outcomes. An International Adult Clozapine Titration Guideline categorizes patients into normal or slow metabolizers. Categorization provides clozapine titration schedules and recommends regular c-reactive protein (CRP) and clozapine concentration monitoring to reduce the risk of adverse drug reactions (ADRs). The impact of the guideline on clozapine ADRs has not been evaluated.

Methods

A retrospective chart review assessed clozapine titrations, laboratory monitoring, ADRs, and discontinuations for clozapine-naive adult inpatients at a single center from January 1, 2013, to June 1, 2022. Each patient's cumulative weekly clozapine dosage was compared with their guideline recommended dosage to create a percent accordance. Linear logistic regression evaluated the relationship between titration speed and the presence of an ADR, while descriptive statistics analyzed laboratory monitoring.

Results

Forty-three patients were included, with the majority being White males with schizophrenia. An inverse relationship existed between the last inpatient week clozapine dose percent accordance and the probability of an ADR. Nonobese patients were less likely than obese patients to experience an ADR (odds ratio = 0.17; 95% CI, 0.03-0.99). CRP and clozapine concentration monitoring was suboptimal.

Discussion

Based on our small retrospective review of primarily White males, more aggressive clozapine titrations did not increase ADRs. Future studies with more diverse samples are needed and should focus on specific ADRs, which may have increased occurrence with rapid titrations. Obese patients were at higher risk of ADRs, correlating with the guideline-recommended slower titrations for these patients.

A systematic review of clozapine-associated inflammation and related monitoring

Clozapine is an effective antipsychotic medication used for treatment-resistant schizophrenia. However, it is underutilized due to rigorous hematologic monitoring requirements and many adverse drug reactions. Publications have highlighted the occurrence of inflammatory reactions, some life-threatening, particularly during the early stages of clozapine treatment. Although guidelines have suggested monitoring for inflammatory processes during clozapine initiation, screening in clinical practice is not universal. This systematic review aimed to investigate the relationship between clozapine and inflammation and assess the importance of monitoring for inflammatory reactions. A comprehensive literature search yielded 6915 unique publication records after removal of duplicates. After a rigorous screening process, 75 publications were included in the review, which focused on three main aspects: (i) the impact of clozapine on inflammatory markers, (ii) monitoring cardiac and other organ function during clozapine-associated inflammatory processes, and (iii) monitoring non-specific signs and symptoms of inflammation. Elevated levels of C-reactive protein (CRP) and several proinflammatory cytokines have been observed in association with clozapine treatment. However, the practicality of measuring specific markers in clinical practice remains uncertain. Current evidence supports monitoring CRP levels during the first 4-8 weeks of treatment, especially to facilitate myocarditis screening. Further research is needed to establish clinically relevant CRP thresholds for intervention. The implementation of monitoring protocols during the early phase of clozapine treatment may mitigate adverse reactions and allow for continued use of clozapine. Future studies should also explore the association between clozapine-associated inflammation and pneumonia, as well as investigate the impact of inflammation on clozapine metabolism to predict the need for dose adjustment. These endeavors may facilitate the development and implementation of evidence-based guidelines for the monitoring of clozapine-associated inflammation.

Hepatoxicity induced by clozapine: Case report and brief review

INTRODUCTION

Antipsychotics are drugs that can produce transient elevations of hepatic enzymes. Clozapine is an atypical antipsychotic used in treatment-resistant schizophrenia and there is evidence that it can produce elevations of hepatic transaminases, expression of liver damage in a hepatocellular pattern.

METHODS

Case report and non-systematic review of the relevant literature.

CASE PRESENTATION

A 39-year-old woman with a diagnosis of paranoid schizophrenia attended the emergency department of a general hospital for nausea, vomiting and jaundice that appeared after the initiation of clozapine. There was no clinical improvement during hospitalisation, and death occurred after 44 days.

LITERATURE REVIEW

Clozapine can increase the liver enzyme levels transiently and asymptomatically; however, there are clinical criteria that recommend the withdrawal of the antipsychotic.

CONCLUSIONS

This is the third case reported in the literature of a fatal outcome of clozapine-induced hepatotoxicity.

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.

Hepatoxicity Induced by Clozapine: Case Report and Brief Review

INTRODUCTION

Antipsychotics are drugs that can produce transient elevations of hepatic enzymes. Clozapine is an atypical antipsychotic used in treatment-resistant schizophrenia and there is evidence that it can produce elevations of hepatic transaminases, expression of liver damage in a hepatocellular pattern.

METHODS

Case report and non-systematic review of the relevant literature.

CASE PRESENTATION

A 39-year-old woman with a diagnosis of paranoid schizophrenia attended the emergency department of a general hospital for nausea, vomiting and jaundice that appeared after the initiation of clozapine. There was no clinical improvement during hospitalisation, and death occurred after 44 days.

LITERATURE REVIEW

Clozapine can increase the liver enzyme levels transiently and asymptomatically; however, there are clinical criteria that recommend the withdrawal of the antipsychotic.

CONCLUSIONS

This is the third case reported in the literature of a fatal outcome of clozapine-induced hepatotoxicity.

Severe drug-induced liver injury in patients under treatment with antipsychotic drugs: Data from the AMSP study

OBJECTIVES

Drug-induced liver injury (DILI) has been associated with various antipsychotic drugs (APDs). Comparative studies between individual APDs are largely not available.

METHODS

Antipsychotic drug utilisation data and reports of severe antipsychotic DILI were assessed by using data from an observational pharmacovigilance programme-Arzneimittelsicherheit in der Psychiatrie (AMSP)-during the period 1993-2016.

RESULTS

Of the 333,175 patients treated with APDs, a total of 246 (0.07%) events of severe DILI were identified. Phenothiazines were associated with significantly higher rates of severe DILI (0.03%, 95% CI = 0.02-0.04) than thioxanthenes (0.01%, 95% CI = 0.00-0.02) or butyrophenones (0.01%, 95% CI = 0.00-0.01). Among individual drugs, olanzapine (0.12%, 95% CI = 0.10-0.16), perazine (0.09%, 95% CI = 0.05-0.15) and clozapine (0.09%, 95% CI = 0.10-0.12 ranked highest. In 78 cases (31.7%), combination therapies with antipsychotic and antidepressant drugs or with two or more APDs were considered responsible. Male sex and a diagnosis of mania were associated with significantly higher rates of severe DILI while older patients (≥65 years old) were significantly less often affected.

CONCLUSIONS

In the present analysis of a representative psychiatric inpatient cohort, olanzapine, perazine, and clozapine were the most common individual APDs associated with severe DILI.

Do proinflammatory cytokines play a role in clozapine-associated glycometabolism disorders?

RATIONALE AND OBJECTIVE

Clozapine (CLZ) is the most effective drug for treatment-resistant schizophrenia but is associated with many side effects, including glycometabolism disorders. Immunological mechanisms may be involved in the development of clozapine side effects. Research relating the immunomodulatory effects of clozapine and its early markers to clinically relevant adverse events is needed to reduce the harmful side effects of clozapine. This study aimed to investigate the role of proinflammatory cytokines in clozapine-associated glycometabolism disorders.

METHODS

We measured the effect of a range of doses of clozapine on glycometabolism-related parameters and proinflammatory cytokines levels in mice peripheral blood. We also examined the differences between these indicators in the peripheral blood of clozapine-treated schizophrenia patients and healthy controls. Furthermore, we detected proinflammatory cytokines expression in mice pancreatic tissue.

RESULTS

Following clozapine administration, glucagon significantly decreased in mouse serum, and proinflammatory cytokine IL-β levels markedly increased. Clozapine reliably increased proinflammatory cytokines (IL-1β, IL-6, and TNF-α) expression in murine pancreatic tissue. Compared with healthy controls, clozapine-treated patients' BMI, blood glucose, and proinflammatory cytokines (IL-1β, IL-6, and TNF-α) increased significantly. In clozapine-treated patients, a higher clozapine daily dosage was associated with higher levels of the proinflammatory cytokines IL-1β and IL-6, and a significant positive correlation was observed between blood glucose levels and the proinflammatory cytokines IL-6 and TNF-α.

CONCLUSION

Findings from animal experiments and clinical trials have shown clear evidence that clozapine has a regulatory effect on immune-related proinflammatory cytokines and influences glycometabolism indicators.

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.

Clozapine Rechallenge Following Neuroleptic Malignant Syndrome: A Systematic Review

PURPOSE/BACKGROUND

Neuroleptic malignant syndrome (NMS) has been described with most antipsychotics, most commonly first generation. Clozapine has also been associated with NMS.

METHODS/PROCEDURES

We conducted a systematic review to identify all studies investigating or describing (a) clozapine rechallenge following suspected NMS associated with clozapine, (b) clozapine use after suspected NMS associated with another antipsychotic, and (c) rechallenge with nonclozapine antipsychotics after suspected clozapine-associated NMS.

FINDINGS/RESULTS

We identified 51 reports detailing 67 cases. Thirty-eight described clozapine administration after NMS on a nonclozapine antipsychotic; 12 described a clozapine rechallenge after an NMS on clozapine monotherapy; and 17 described the use of nonclozapine antipsychotics after an NMS on clozapine. The outcome of clozapine rechallenge was favorable (no recurrence of NMS) in 92% (n = 11) of cases after an NMS on clozapine and in 79% (n = 30) of those prescribed clozapine following NMS on a nonclozapine antipsychotic. Most (82%; n = 14) cases after NMS on clozapine had no recurrence of NMS on receiving a nonclozapine antipsychotic.No mortality was reported with any of these interventions.

IMPLICATIONS/CONCLUSIONS

Our findings suggest that rechallenge following clozapine NMS is possible, and with careful risk-benefit analysis consideration, a clozapine rechallenge can be made. A publication bias in favor of cases in which rechallenge was successful is probable and is an important limitation.

Clinical determinants of fever in clozapine users and implications for treatment management: A narrative review

OBJECTIVES

To identify the clinical determinants of fever in clozapine users and their impact on management of clozapine treatment.

METHODS

Articles published in English or French identified with a MEDLINE, Web of Sciences, Cochrane Library and PsycINFO search, from inception through February 2019, using the term "clozapine" in combination with "fever" OR "hyperthermia" OR "body temperature" OR "pyrexia" OR "febrile" OR "heat" OR "thermoregulation". Information extracted for each medical condition were frequency, time to onset after initiation of clozapine treatment, characteristics of fever, associated symptoms, laboratory tests used for diagnosis, course, lethality, discontinuation of clozapine. Data were synthesized narratively.

RESULTS

Our search yielded 394 unique hits published from 1993 to 2018. We included 73 articles in the review: two meta-analyses, 14 reviews, six epidemiological studies, 11 clinical studies and 40 case reports. During clozapine initiation, fever is most frequently benign and transient but should be closely monitored as it may be the first stage of potentially life-threatening adverse drug reactions (ADR) (agranulocytosis, neuroleptic malignant syndrome myocarditis, hepatitis, pancreatitis, nephritis, colitis, etc.). Other ADR associated with fever are independent of duration of exposure to clozapine (heat stroke, pneumonia, pulmonary embolism, necrotizing colitis). If fever is due to intercurrent infection, therapeutic drug monitoring is recommended to adjust clozapine daily dosage.

CONCLUSION

Benign causes of fever are much more frequent than life-threatening ADR during clozapine treatment. Discontinuation should not be considered as automatic in the event of fever, especially during the early phase of clozapine initiation.

Clozapine-induced interstitial nephritis in a patient with schizoaffective disorder in the forensic setting: a case report and review of the literature

We present a rare case of Acute Interstitial Nephritis (AIN) that occurred following a re-trial of clozapine in a 56-year-old lady with schizoaffective disorder. On initial trial of clozapine, this patient felt generally unwell with respiratory symptoms. Her inflammatory markers were raised and her renal function showed a mild, transient deterioration which normalised on the day of cessation of clozapine. Two years later, clozapine was re-trialled due the refractory nature of her psychiatric symptoms. She subsequently developed renal failure and AIN was confirmed by renal biopsy. Renal function improved after cessation of clozapine; however, she never fully regained normal renal function.

Treatment resistant schizophrenia - review and a call to action

Recovery rates in schizophrenia remain suboptimal with up to one-third resistant to standard treatments, a population prevalence of 0.2%. Clozapine is the only evidenced-based treatment for treatment resistant schizophrenia (TRS), yet there are significant delays in its use or it may not be trialled, potentially impacting the chance of recovery. Better outcomes with earlier use of clozapine may be possible. There is emerging evidence that early treatment resistance is not uncommon from the earliest stages of psychosis. In this review, we provide an update on TRS, its epidemiology and its management, with a specific focus on the optimal use and timing of clozapine and augmentation strategies for the one-third of patients who do not respond to clozapine.