Patients with schizophrenia have a significantly elevated risk of mortality. Clozapine is effective for treatment-resistant schizophrenia, but its use is limited by side-effects. Understanding its association with mortality risk is crucial.

To investigate the associations of clozapine with all-cause and cause-specific mortality risk in schizophrenia patients.

In this 18-year population-based cohort study, we retrieved electronic health records of schizophrenia patients from all public hospitals in Hong Kong. Clozapine users (ClozUs) comprised schizophrenia patients who initiated clozapine treatment between 2003 and 2012, with the index date set at clozapine initiation. Comparators were non-clozapine antipsychotic users (Non-ClozUs) with the same diagnosis who had never received a clozapine prescription. They were 1:2 propensity score matched with demographic characteristics and physical and psychiatric comorbidities. ClozUs were further defined according to continuation of clozapine use and co-prescription of other antipsychotics (polypharmacy). Accelerated failure time (AFT) models were used to estimate the risk of all-cause and cause-specific mortality (i.e. suicide, cardiovascular disease, infection and cancer).

This study included 9,456 individuals (mean (s.d.) age at the index date: 39.13 (12.92) years; 50.73% females; median (interquartile range) follow-up time: 12.37 (9.78–15.22) years), with 2020 continuous ClozUs, 1132 discontinuous ClozUs, 4326 continuous non-ClozUs and 1978 discontinuous Non-ClozUs. Results from adjusted AFT models showed that continuous ClozUs had a lower risk of suicide mortality (acceleration factor 3.01; 99% CI: 1.41–6.44) compared with continuous Non-ClozUs. Continuous ClozUs with co-prescription of other antipsychotics exhibited lower risks of suicide mortality (acceleration factor 3.67; 1.41–9.60) and all-cause mortality (acceleration factor 1.42; 1.07–1.88) compared with continuous Non-ClozUs. No associations were found between clozapine and other cause-specific mortalities.

These results add to the existing evidence on the effectiveness of clozapine, particularly its anti-suicide effects, and emphasise the need for continuous clozapine use for suitable patients and the possible benefit of clozapine polypharmacy.

Clozapine is the only licensed medication for treatment-resistant schizophrenia, although it is underused. Healthcare professionals (medical and non-medical professionals) play a crucial role in the management of clozapine. Consultant psychiatrists are accountable for the initiation of clozapine, whereas non-medical professionals are often responsible for the monitoring, the management of side effects and patient education. It appears that healthcare professionals‘ (HCPs) competence and confidence may have an effect on clozapine underutilisation.

To synthesise the most pertinent literature examining the factors influencing HCPs competence and confidence in the management of clozapine and how these factors influence variation in prescribing practice.

A review of the literature focusing on these elements was conducted. The Population, Context, Outcome (PCO) framework was adopted to support the literature search. The databases Medline, Psychinfo, Scopus, Cinahl, Pubmed, Embase, British Library, Ethos e-thesis, Google Scholar, Dart Europe e-thesis were consulted; the search was completed in January 2025. Screening, selection, data extraction and quality assessment were conducted independently by two researchers. Thematic analysis was used to investigate and compare the data emerging from the studies.

Thirty-four articles were included in the review. Six themes were identified: attitude toward and knowledge about clozapine, misconceptions (regarding side effects, monitoring and co-morbidities), guidelines, education, training and experience. HCPs self-reported as competent with guidelines (local and national), yet they expressed less confidence in their ability to adhere to them and were uncertain about managing side effects. Lack of education, training and insufficient exposure to clozapine management were significant factors impacting competence and confidence, resulting in clozapine underuse and variance in prescribing practice. The review highlighted a gap in the literature, as only a few studies involving non-medical professionals were found.

A general lack of education and training related to clozapine use was identified amongst all professionals.

The impact of educational programmes on improving competence and enhancing confidence was considered positive, however when integrated with clinical practice.

The studies identified in this review were lacking in the involvement of non-medical professionals. Given their crucial role in managing side effects and educating patients and carers, it is evident that their inclusion in future research is imperative.

Psychotic disorders are severe mental health conditions frequently associated with long-term disability, reduced quality of life and premature mortality. Early Intervention in Psychosis (EIP) services aim to provide timely, comprehensive packages of care for people with psychotic disorders. However, it is not clear which components of EIP services contribute most to the improved outcomes they achieve.

We aimed to identify associations between specific components of EIP care and clinically significant outcomes for individuals treated for early psychosis in England.

This national retrospective cohort study of 14 874 EIP individuals examined associations between 12 components of EIP care and outcomes over a 3-year follow-up period, by linking data from the National Clinical Audit of Psychosis (NCAP) to routine health outcome data held by NHS England. The primary outcome was time to relapse, defined as psychiatric inpatient admission or referral to a crisis resolution (home treatment) team. Secondary outcomes included duration of admissions, detention under the Mental Health Act, emergency department and general hospital attendances and mortality. We conducted multilevel regression analyses incorporating demographic and service-level covariates.

Smaller care coordinator case-loads and the use of clozapine for eligible people were associated with reduced relapse risk. Physical health interventions were associated with reductions in mortality risk. Other components, such as cognitive–behavioural therapy for psychosis (CBTp), showed associations with improvements in secondary outcomes.

Smaller case-loads should be prioritised and protected in EIP service design and delivery. Initiatives to improve the uptake of clozapine should be integrated into EIP care. Other components, such as CBTp and physical health interventions, may have specific benefits for those eligible. These findings highlight impactful components of care and should guide resource allocation to optimise EIP service delivery.

Clozapine is the antipsychotic of choice for people with treatment-resistant schizophrenia (TRS) but is associated with the uncommon but potentially life-threatening adverse effect of myocarditis. However, there are no criteria for diagnosing clozapine-associated myocarditis (CAM) or global guidelines on detection and risk reduction, or for restarting clozapine after CAM.

To develop criteria for CAM and algorithms for clozapine initiation and clozapine rechallenge after CAM in a multiprofessional consensus process.

We conducted a systematic literature search for cases of clozapine rechallenge following CAM using the PubMed, EMBASE, CINAHL and PsycINFO databases, followed by a multidisciplinary international two-step Delphi consensus process in July and October 2024. The Delphi panel comprised psychiatrists, cardiologists, pharmacists, psychopharmacologists and nurses with expertise on clozapine or myocarditis.

Ninety-three clinicians and academics with experience in prescribing clozapine from six continents participated in the Delphi process. A consensus was reached on a definition of CAM according to modified clinical criteria from the European Society of Cardiology for myocarditis associated with immune checkpoint inhibitors. Titration schemes slower than those given in the Summary of Product Characteristics for clozapine were recommended to minimise CAM risk. Minimum and enhanced requirements for screening and monitoring were developed to account for global perspectives and limited resources in certain healthcare systems, and an approach to clozapine rechallenge was elaborated.

This multidisciplinary project represents the first guidance for CAM and will inform clinicians, other caregivers and patients, as well as facilitating the development of national guidelines on CAM prevention, screening and monitoring and rechallenge after an index episode of myocarditis in individuals taking clozapine.

Clozapine-induced gastrointestinal hypomotility (CIGH) can cause constipation, which may progress to ileus, intestinal perforation and other life-threatening conditions. There were at least 527 unique cases of harmful CIGH (172 deaths) assessed by strict criteria in the UK, 1992–2017.

To assess the impact of strengthened warnings about the risks of CIGH, such as those issued by the UK Medicines and Healthcare products Regulatory Agency (MHRA) (2017) and the US Food and Drug Administration (2020), on reports of harmful CIGH in the UK.

We audited UK MHRA Yellow Card reports recorded as clozapine-related gastrointestinal disorders, 2018–end 2022.

Of 335 unique reports (36 fatal, 26 male) that met initial CIGH criteria, there were 129 (22 fatal, 18 male) that met the final CIGH inclusion criteria. Reports of non-fatal CIGH (final criteria) averaged 26 per year (15 in 2022). Deaths averaged four per year (two in 2022). Where data were available the greatest proportion of deaths occurred after 10–14 years of clozapine treatment.

Publicity aimed at raising awareness of the problem posed by CIGH has been associated with a reduction in harmful CIGH as reported to the UK MHRA since 2017. Continued vigilance is needed to reduce risk. Stopping smoking may pose a particular risk and should be monitored carefully.

Clozapine-induced gastrointestinal hypomotility and constipation can result in severe and sometimes fatal gastrointestinal complications. Laxatives should be prophylactically prescribed with clozapine, but this is inconsistently achieved. Digital clinical decision support (CDS) alerts can promote safer prescribing.

To evaluate whether a CDS alert could promote timely laxative use with clozapine in hospital.

Retrospective in-patient prescribing data was used to compare co-prescribing of laxatives for first clozapine prescriptions pre-alert (January 2017–September 2019) and post-alert (September 2019–December 2023) implementation across 1194 hospital admissions where clozapine was prescribed. Regular non-bulking laxative and any laxative co-prescribing for first clozapine prescriptions within 24 h were assessed. Multivariable logistic regression was performed to determine the impact of alert implementation on laxative co-prescribing.

Of the 1194 admissions included, 449 admissions had clozapine prescribed pre-alert implementation and 745 admissions had post-alert implementation. Regular non-bulking laxative co-prescription occurred for 67.0% of first clozapine prescriptions pre-alert and 76.1% post-alert (P < 0.001). Any laxative co-prescription occurred for 87.3% of first clozapine prescriptions pre-alert and 96.5% post-alert (P < 0.001). Alert implementation was associated with increased likelihoods of regular non-bulking laxative co-prescribing (odds ratio, 1.341; 95% CI, 1.021–1.756; P = 0.035) and any laxative co-prescribing (odds ratio, 3.487; 95% CI, 2.135–5.838; P < 0.001) for first clozapine prescriptions within 24 h.

CDS alert implementation was associated with increased and earlier laxative co-prescribing for clozapine. Our findings suggest that a CDS alert is an effective tool for promoting timely laxative use with clozapine in hospital.

Clozapine is the antipsychotic medication with the greatest efficacy in treatment-resistant schizophrenia (TRS). Unfortunately, clozapine is ceased in approximately 0.2% to 8.5% of people due to concerns about clozapine-associated myocarditis (CAM). The opportunity for clozapine rechallenge is important for people with TRS and CAM, due to limited alternative treatments. However, there is a lack of consensus regarding the optimal process, monitoring, and dose titration to achieve successful clozapine rechallenge. The study aimed to review the process, monitoring, and dose titration within cases of clozapine rechallenge after CAM, to identify features associated with successful rechallenge.

A systematic review of clozapine rechallenge cases following CAM was conducted. PubMed, EMBASE, Cinahl, and PsycINFO were searched for cases. Reference lists of retrieved articles and field experts were consulted to identify additional studies.

Forty-five cases were identified that described clozapine rechallenge, 31 of which were successful. Successful rechallenge cases generally used a slower dose titration regime with more frequent monitoring than standard clozapine initiation protocols; however, this data was not always completely recorded within cases. Six cases referred to published rechallenge protocols to guide their rechallenge.

The process, monitoring, and dose titration of clozapine rechallenge are inconsistently reported in the literature. Despite this, 69% of case reports detailed a successful rechallenge post CAM; noting limitations associated with reliance on case data. Ensuring published clozapine rechallenge cases report standardised data, including titration speed and monitoring frequencies, is required to guide the development and validation of guidelines for clozapine rechallenge.

Clozapine therapy presents a risk of agranulocytosis, necessitating monitoring of white blood cell count. The detection of benign ethnic neutropenia (BEN), in which neutropenia can be present without an increased risk of infection, is particularly important in preventing unnecessary withdrawal of clozapine. BEN is strongly linked to the CC homozygote of the single nucleotide polymorphism rs2814778 in the atypical chemokine receptor-1 (ACKR1) gene.

We introduced voluntary genetic testing for BEN in one of our clozapine clinics, with the aim of assessing the prevalence of undiagnosed BEN in patients on clozapine.

We offered genetic testing for BEN to patients undergoing medium- and long-term clozapine treatment, and conducted a comparative analysis of neutrophil counts across three identified groups: those previously diagnosed with BEN, those with newly discovered BEN and those confirmed by genetic testing not to have BEN.

We conducted genetic testing for BEN on 108 patients. Of these, 16 were already registered as having BEN and had the CC homozygote. A further 26 patients (24% of the cohort) who were previously not diagnosed with BEN by standard haematological monitoring were found to have the CC homozygote on genetic testing. Unadjusted mean neutrophil counts were lowest for those with previously diagnosed BEN (2.5 × 109/L, 95% CI 2.2–2.8; P < 0.001 v. other groups), but those with newly discovered BEN had mean counts that were significantly lower (4.1 × 109/L, 95% CI 3.6–4.7) than those with TT and CT genotypes (5.1 × 109/L, 95% CI 4.7–5.4; P = 0.006).

Undiagnosed BEN was common in our naturalistic cohort. The integration of genetic testing into standard monitoring would enhance the management of clozapine therapy, potentially allowing for the safe reintroduction or continuation of clozapine in patients with hitherto unrecognised BEN. All current and prospective clozapine patients should be genetically tested for BEN.

Clozapine is an atypical antipsychotic crucial for treatment-resistant schizophrenia, characterised by its multi-receptor targeting, including serotonin (5-HT2A, 5-HT2C) and dopamine (D1, D2, D3, D4) receptors, among others. This broad mechanism is effective against positive symptoms of schizophrenia with a lower incidence of extrapyramidal side effects. However, clozapine poses significant haematological risks, notably agranulocytosis, necessitating stringent blood monitoring protocols.

This study examined haematological parameters in 157 patients on clozapine therapy, analysing the prevalence and clinical correlations of haematological abnormalities such as leucocytosis, thrombocytosis, and alterations in red blood cell distribution width (RDW) and mean platelet volume (MPV).

The findings revealed leucocytosis in 36.9% of patients, thrombocytosis in 8.9%, and elevated RDW in 23.6%. Notably, higher clozapine doses were associated with leucocytosis, though no significant correlations were found between clozapine dose, duration of use, and changes in RDW, mean corpuscular haemoglobin concentration, or MPV.

The study’s results underscore the necessity of regular haematological monitoring to mitigate the risks of clozapine therapy while leveraging its therapeutic benefits. Additionally, the study suggests personalised dosing strategies to balance efficacy and safety, particularly in managing clozapine-induced haematological changes.

Although clozapine is the most effective antipsychotic for people with treatment-resistant schizophrenia (TRS), only 40% of people with TRS respond, and there is limited evidence for augmentation agents. Cannabidiol (CBD) reduces positive symptoms in individuals with schizophrenia, but no trials have specifically examined its efficacy in those with clozapine-resistant schizophrenia.

To examine the clinical efficacy of CBD augmentation in people with clozapine-resistant schizophrenia.

This is a 12-week randomised, placebo-controlled, double-blind, parallel-group trial (registration number: ACTRN12622001112752). We will recruit 88 individuals with clozapine-resistant schizophrenia, randomised (1:1) to 1000 mg daily CBD versus placebo. Eligible individuals will be aged between 18 and 64 years, fulfil DSM-IV criteria for schizophrenia or schizoaffective disorder, have a total PANSS (Positive and Negative Syndrome Scale) score ≥60, have received oral clozapine for at least 18 weeks and have a clozapine level of >350 ng/mL. Interim analyses will be conducted at 25, 50 and 75% recruitment; these will also provide an opportunity to reallocate participants dependent on conditional power. The primary endpoint will be the difference in PANSS positive scores at the end of week 12. Secondary endpoints include depression, anxiety, sleep, quality of life, alcohol consumption, change in weight and metabolic syndrome components, and neurocognitive measures, as well as safety and tolerability.

Novel treatments for clozapine-resistant schizophrenia are urgently needed. If found to be effective, CBD may have a role as a novel and safe adjunct to clozapine.