Sodium valproate and clozapine induced neutropenia: A case control study using register data

Severe neutropenia unrelated to clozapine in patients receiving clozapine

BACKGROUND

Clozapine is known to cause agranulocytosis. Mandatory monitoring schemes are aimed at reducing the risk of agranulocytosis and of the consequences of agranulocytosis. All cases of agranulocytosis occurring in people prescribed clozapine are assumed to be caused by clozapine.

METHODS

In a previous study, we examined a cohort of patients listed on our hospital database as having had clozapine-induced agranulocytosis and applied specific criteria to identify those with confirmed clozapine-related, life-threatening agranulocytosis. In this study, we examine the cases not meeting these specific criteria.

RESULTS

In the original study, 9 of 23 cases met the criteria for clozapine-induced, life-threatening agranulocytosis. Of the 13 remaining cases for whom data were available, 5 were probably caused by clozapine but were not life-threatening. Three cases were the result of concomitant cancer chemotherapy. Three were anomalous results probably related to measurement error. For the remaining two cases, the cause was not identified.

CONCLUSION

Not all cases of agranulocytosis occurring in people taking clozapine are caused by clozapine. The widely used threshold criterion-based diagnosis overestimates the risk of agranulocytosis. True clozapine-related agranulocytosis is best identified by pattern-based criteria: rapid fall in neutrophil counts over around 2 weeks to below 0.5 × 109/L for two consecutive days (unless clozapine is stopped very early or granulocyte colony stimulating factor is given) where other possible causes (benign ethnic neutropenia, cancer chemotherapy) can be ruled out.

Decoding Clozapine-Induced Agranulocytosis: Unraveling Interactions and Mitigation Strategies

Agranulocytosis represents a severe complication associated with the administration of clozapine. Clozapine is an antipsychotic medication that has demonstrated substantial efficacy in remediating refractory schizophrenia and various other psychiatric disorders. Nonetheless, it is crucial to monitor patients for neutropenia regularly during clozapine therapy. Therefore, this article aimed to delve into the prevalence of agranulocytosis during clozapine treatment by scrutinizing the extant literature to discern trends and correlations. This review endeavored to explore factors such as drug interactions, dose-related factors, duration of treatment, and genetic predispositions that could potentially influence the likelihood of patients developing agranulocytosis while undergoing clozapine therapy. Moreover, this review enunciates the ramifications of agranulocytosis on both patients and healthcare providers and meticulously evaluates the strategies to mitigate this risk and ensure optimal patient outcomes.

Risk of clozapine-associated agranulocytosis and mandatory white blood cell monitoring: Can the regulations be relaxed?

After the introduction of clozapine eight Finnish patients died after developing agranulocytosis. Clozapine was withdrawn from the market and only reintroduced with strict mandatory white blood cell monitoring as long as treatment lasts and thresholds at which clozapine must be discontinued definitively. The fear of agranulocytosis and the need for intensive blood monitoring is the single most important barrier for prescribers and patients alike and leads to underprescription of the only effective and approved medication for treatment-resistant schizophrenia. We summarize evidence that the risk of agranulocytosis is smaller than perceived at the time of reintroduction, is concentrated in the first 18 weeks of treatment, is not greater than with other antipsychotics thereafter and that frequent blood monitoring has not demonstrably decreased the rate of agranulocytosis. Therefore we propose 1) mandatory monitoring of the absolute neutrophil count (ANC) exclusively during the first 18 weeks of clozapine treatment, 2) that thereafter the prescriber and the well-informed patient decide together about further monitoring frequency, 3) that clozapine treatment must be stopped if the ANC falls below 1.0 × 109/L. Continuation of clozapine or a rechallenge are possible if prescriber and patient determine that the benefits outweigh the risks. 4) National registries which control the haematologic monitoring are unnecessary and do not help to reduce clozapine-induced agranulocytosis. They should at least be restricted to the first 18 weeks of clozapine use.

Optimizing co-prescription of clozapine and antiseizure medications: a systematic review and expert recommendations for clinical practice

INTRODUCTION

Antiseizure medication (ASM) add-on to clozapine may be efficient to target clozapine-resistant mood or psychotic symptoms or clozapine-related adverse drug reactions (ADR) such as seizures. We aimed to synthesize the information relevant for clinical practice on the risks and benefits of clozapine-ASM co-prescription.

AREAS COVERED

Articles were identified with MEDLINE, Web of Sciences and PsycINFO search from inception through October 2023. The review was restricted to ASM with mood-stabilizing properties or with potential efficacy for resistant psychotic symptoms (valproate (VPA), lamotrigine, topiramate, carbamazepine, oxcarbazepine).

EXPERT OPINION

VPA add-on to clozapine is associated with a high risk of serious ADR (myocarditis, neutropenia, pneumonia) mostly explained by complex time-dependent drug-drug interactions. The initial inhibitory effects on clozapine metabolism require slow titration to avoid immuno-allergic reactions. After the titration period, VPA has mainly inductive effects on clozapine metabolism that are more marked in smokers requiring therapeutic drug monitoring. Lamotrigine and topiramate add-on may be recommended as the first-line treatment for clozapine-related seizures, but there is limited evidence regarding the efficacy of this strategy for clozapine-resistant psychotic symptoms. Carbamazepine should not be co-prescribed with clozapine because of its potential for agranulocytosis and for inducing clozapine metabolism.

Novel Identification of Cysteinyl Derivatives of Toxic Clozapine Nitrenium Ions and the Effect of Valproic Acid on Metabolite Formation: A Study Using Reprocessed High-Resolution Mass Spectra of Analyzed Therapeutic Drug Monitoring Samples

BACKGROUND

Clozapine (CLZ) use is hampered by the risk of granulocyte toxicity, which is associated with the formation of nitrenium ions and the concurrent use of valproic acid (VPA). These highly reactive nitrenium ions cannot be measured in vivo. Instead, deactivated cysteinyl conjugates may potentially be detected. The aim of this study was to develop a novel method for identifying cysteinylated derivates of CLZ nitrenium ions to investigate the effect of VPA on their formation using therapeutic drug monitoring data.

METHODS

A population comprising 93 VPA comedicated and 162 control patients from a therapeutic drug monitoring (TDM) service in Oslo, Norway, was included. Reprocessing of ultraperformance liquid chromatography high-resolution mass spectra (UHPLC-HR-MS) of previously analyzed TDM samples, combined with the assessment of MS/MS fragmentation patterns, was performed to identify the CLZ cysteinyl conjugates. Smoking, which induces CLZ metabolism, was assessed by detecting cotinine in the reprocessed mass spectra.

RESULTS

By reprocessing the UHPLC-HR-MS files of the TDM analyses and reviewing the MS/MS fragment profiles, four cysteinyl conjugates of CLZ were identified. The formations of CLZ cysteinyl (CLZ-Cys 1+ ) and CLZ- N -oxide cysteinyl (CLZ-NOX-Cys 1+ ) were 1.5-fold ( P = 0.038) and 2.1-fold ( P < 0.001) higher in VPA-treated patients than those in the controls. In agreement with previous studies, a 45% reduction in N -desmethylclozapine formation was observed in VPA-treated patients ( P < 0.001).

CONCLUSIONS

A novel method for detecting cysteinyl conjugates of CLZ was developed. Application of this method indicated that VPA significantly increased the formation of CLZ-Cys 1+ metabolites, which might explain the granulocyte toxicity reported after adding VPA to CLZ treatment. The developed method opens new avenues for investigating CLZ toxicity, e.g. by correlating cysteinyl conjugates and granulocyte counts in patients.

Valproate-related neutropenia and lithium-related leukocytosis in patients treated with clozapine: a retrospective cohort study

BACKGROUND

Neutropenia is a noteworthy side effect of clozapine, which might warrant this drugs' discontinuance for safety. Studies have revealed that the risk of neutropenia increases with concurrent administration of valproate, but the evidence was limited. Conversely, lithium may have an ameliorating effect on clozapine-induced neutropenia. This study explored the effects of valproate and lithium on white blood cell counts in patients treated with clozapine.

METHODS

We retrospectively investigated the electronic medical records from one tertiary psychiatric hospital in Taiwan and enrolled patients discharged between January 1, 2006, and December 31, 2017, with clozapine prescriptions. We scrutinized their demographic data, medications, and hematological results at discharge and during follow-up outpatient clinic visits over the subsequent 3 years. Patients were classified into four groups: clozapine only (CLO), clozapine and valproate (CLO + VAL), clozapine and lithium (CLO + Li), and clozapine, valproate, and lithium (CLO + VAL + Li). We also identified hematological events (neutropenia or leukocytosis) of these patients during outpatient follow-ups.

RESULTS

Of the included 1084 patients, 55(5.1%) developed neutropenia. Concurrent valproate use (odds ratio [OR] = 3.49) and older age (p = .007) were identified as risk factors. Moreover, 453 (41.79%) patients developed leukocytosis. Younger age; male sex; and concurrent use of lithium (OR = 3.39, p < .001), clozapine daily dosage, and benzodiazepines were the risk factors for leukocytosis.

CONCLUSION

Concurrent valproate use and older age are associated with the development of neutropenia in patients treated with clozapine. Concurrent lithium usage, younger age, male sex, and concurrent benzodiazepine use might be related to leukocytosis.

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.

Pharmacokinetic interactions between clozapine and valproic acid in patients with treatment-resistant schizophrenia: Does UGT polymorphism affect these drug interactions?

The combination of valproic acid (VPA) and clozapine (CLZ) is regularly prescribed for augmentation therapy in treatment resistant schizophrenia. The VPA has been shown to reduce norclozapine (NCLZ) plasma levels, but the mechanism of this interaction remains unknown. The aim of this study is to examine the differences between patients treated with CLZ and patients treated with CLZ plus VPA. For it, various factors have been evaluated. The study was based on plasma samples from CLZ and CLZ plus VPA treated patients (n = 61) subjected to routine therapeutic drug monitoring considering clinical data, smoking status, daily dose of CLZ and VPA, concomitant medications, albumin, and renal and hepatic function. Genotyping of polymorphisms of CYP1A2, CYP3A4/5, CYP2C19, ABCB1, UGT2B10 and CYP2C19 were performed by real time PCR. CYP2D6 were genotyped using competitive allele-specific PCR and by a long PCR based method. Plasma CLZ and NCLZ concentrations were measured by Liquid Chromatography-Tandem masses (LC-MS/MS) and plasma VPA by Ultraviolet-Visible (UV-vis) spectrophotometric immunoassay. The patients presented adequate CLZ levels in relation to the dose. However, NCLZ levels were excessively low and the CLZ/NCLZ ratio very high. Patients with UGT2B10 GT (rs61750900) genotype showed lower NCLZ plasma levels and C/D NCLZ, and higher CLZ/NCLZ ratio versus patients with UGT2B10 GG genotype. VPA, smoking, the presence of UGT2B10 GT genotype and having low albumin levels indicate that the CLZ/NCLZ ratio is affected, mostly coinciding with decreased NCLZ levels and possibly with an increased risk of neutropenia.

Effect of Valproic Acid on the Metabolic Spectrum of Clozapine in Patients With Schizophrenia

BACKGROUND

Valproic acid (VPA) is frequently used with clozapine (CLZ) as mood stabilizer and/or seizure prophylaxis. Valproic acid is known to reduce N-desmethylclozapine (N-DMC) but not CLZ levels. This leads to the hypothesis that VPA induces the CLZ metabolism via non-N-desmethylation pathways. Therefore, we aimed to investigate the effect of concurrent VPA use on the serum concentrations of a spectrum of CLZ metabolites in patients, adjusting for smoking.

METHODS

In total, 288 patients with an overall number of 737 serum concentration measurements of CLZ and metabolites concurrently using VPA (cases, n = 22) or no interacting drugs (controls, n = 266) were included from a routine therapeutic drug monitoring service. Linear mixed model analyses were performed to compare the dose-adjusted concentrations (C/D) of CLZ, N-DMC, CLZ 5N/N+-glucuronides, and metabolite-to-parent ratios in cases versus controls.

RESULTS

After adjusting for covariates, the N-DMC (-40%, P < 0.001) and N+-glucuronide C/Ds (-78%, P < 0.001) were reduced in cases versus controls, while the CLZ C/D was unchanged (P > 0.7). In contrast, the 5N-glucuronide C/D (+250%, P < 0.001) and 5N-glucuronide-to-CLZ ratios (+120%, P = 0.01) were increased in cases versus controls.

CONCLUSIONS

Our findings show that complex changes in CLZ metabolism underly the pharmacokinetic interaction with VPA. The lower levels of N-DMC seem to be caused by VPA-mediated induction of CLZ 5N-glucuronide formation, subsequently leading to reduced substrate availability for N-desmethylation. Whether the changes in CLZ metabolism caused by VPA affects the clinical outcome warrants further investigation.

Clozapine rechallenge following neutropenia using granulocyte colony-stimulating factor: A Quebec case series

BACKGROUND

Clozapine has a unique efficacy profile among individuals suffering from treatment-resistant schizophrenia, but is associated with hematological side effects. The use of granulocyte colony-stimulating factors (G-CSF) to allow clozapine continuation or rechallenge has emerged as a promising option, but evidence is still scarce.

AIM

To describe the largest case series so far published regarding this practice.

METHOD

A national clozapine hematological monitoring database was consulted to identify all patients who had had neutrophil count <1.5 × 10⁹/L since 2004 in Quebec and was cross-referenced with hospital pharmacy software to identify patients who had received at least one dose of G-CSF, such as filgrastim, while being exposed to clozapine. All data were collected retrospectively, using patients' medical files, from January to July 2019.

RESULTS

Using G-CSF, three out of eight patients could maintain clozapine despite neutropenia episodes that otherwise would have required treatment discontinuation. The only side effect reported was mild short-lived back pain, over a mean 3-year follow-up period. In all but one case, filgrastim was used on an "as-needed" basis at doses of 300 mcg administered subcutaneously.

CONCLUSION

These results suggest that the "as-needed" use of G-CSF is well-tolerated and may allow clozapine rechallenge in some well-selected patients, adding to the paucity of data regarding long-term safety and efficacy of this strategy. More research may help to better define potential candidates and optimal regimen of such practice.

Therapeutic drug monitoring of clozapine in adults with schizophrenia: a review of challenges and strategies

INTRODUCTION

Clozapine (CLZ) is the superior drug in treatment of schizophrenia. Serum concentration of CLZ is associated with clinical response and dose-dependents side effects, where generalized tonic-clonic seizures are most critical. Thus, therapeutic drug monitoring (TDM) of CLZ may guide individual dosing to reach target exposure and prevent dose-dependent side effects. However, current TDM methods are not capable of predicting the risk of agranulocytosis, which is a dose-independent side effect restricting use of CLZ to treatment-resistant schizophrenia (TRS).

AREAS COVERED

The article provides an overview of clinical, pharmacological, and toxicological aspects of CLZ, and the role of TDM as a tool for dose titration and follow-up in patients with TRS. Main focus is on current challenges and strategies in CLZ TDM, including future perspectives on potential identification/analysis of CLZ metabolite biomarkers reflecting the risk of granulocyte toxicity.

EXPERT OPINION

The association between CLZ serum concentration, clinical response and risk of seizures is indisputable. TDM should therefore always guide CLZ dose titration. Development of advanced TDM methods, including biomarkers predicting the risk of granulocyte toxicity might extend TDM to be a tool for deciding which patients that can be treated safely with CLZ, potentially increasing its utility beyond TRS.

Risk factors for early-phase clozapine discontinuation: A nested case-control study

OBJECTIVES

Safe and efficient methods for introducing clozapine to patients with treatment-resistant schizophrenia (TRS) are needed. We investigated risk factors for clozapine discontinuation in the early phase of its introduction.

METHODS

We conducted a nested case-control study at 14 psychiatric hospitals in Chiba, Japan. Data from pre-registered TRS patients were collected at 7 time points within 12 weeks before and after the start of clozapine introduction. We examined the demographic data, prior and concomitant psychotropic drugs, strategies for switching from prior antipsychotics, and blood test and Global Assessment of Function results. The Clinical Global Impression-Severity Scale was retrospectively scored at 12 weeks before and after clozapine introduction.

RESULTS

Of 228 patients, clozapine treatment was continued in 213 (93.4 %) and discontinued in 15 (6.6 %) patients within 12 weeks. Clinical symptoms were improved to mild symptoms with a response rate of 14.9 %. Prior antipsychotics and concomitant psychotropic drugs except for mood stabilizers were significantly decreased. Histories of smoking (OR = 3.32, 95 %CI: 1.11-9.93) and antipsychotic treatment at chlorpromazine-equivalent doses <1200 mg within the past 5 years (OR = 3.93, 95 %CI: 1.24-12.50), but not antipsychotic switching strategy, were associated with clozapine discontinuation. Eosinophilia was the most frequent reason for discontinuation (n = 3, 20 %) and was associated with concomitant valproate at 4 weeks after the introduction.

CONCLUSION

Clozapine is an effective option for TRS patients (especially those treated with higher doses of prior antipsychotics) in Japan. Clinicians should be cautious about concomitant valproate in the early phase of clozapine introduction due to a high risk of eosinophilia.

There Is Life After the UK Clozapine Central Non-Rechallenge Database

BACKGROUND AND AIMS

In the United Kingdom, patients on clozapine whose hematological parameters fall below certain thresholds are placed on the Central Non-Rechallenge Database (CNRD), meaning that they cannot be prescribed clozapine again except under exceptional circumstances. This practice was discontinued in the United States in 2015 by expanding the hematological monitoring guidelines, allowing more patients to receive clozapine. Our objective was to investigate the implications this policy change would have on clozapine utilization in the United Kingdom.

METHODS

This was an observational, retrospective analysis of patients registered on the CNRD in a large mental health trust. The first objective was to compare the number of patients placed on the CNRD under the United Kingdom and the US Food and Drug Administration (FDA) criteria. The second objective was to explore the hematological and clinical outcomes of CNRD patients. The third objective was to investigate the hematological outcomes of patients rechallenged on clozapine after nonrechallengeable status.

RESULTS

One hundred and fifteen patients were placed on CNRD from 2002 to 2019, of whom 7 (6%) met the equivalent criteria for clozapine discontinuation under the FDA guidelines. Clinical outcomes, as measured by the Clinical Global Impression-Severity scale, were worse 3 months after clozapine cessation than on clozapine (t = -7.4862; P < .001). Sixty-two (54%) patients placed on CNRD were rechallenged. Fifty-nine of those (95%) were successfully rechallenged; 3 patients were placed back on CNRD, only one of which would have had to stop clozapine again under FDA criteria.

CONCLUSION

Implementation of the updated FDA's monitoring criteria in the United Kingdom would significantly reduce clozapine discontinuation due to hematological reasons. The evidence suggests an urgent need for revising the UK clozapine monitoring guidelines to improve outcomes in treatment-resistant schizophrenia.

Clozapine-associated neutropenia following augmentation with sodium valproate

Clozapine is gold standard for the management of treatment-resistant schizophrenia. It can offer life-changing symptom reduction where other antipsychotics have failed, and for these patients, treatment with clozapine should be maintained, if in any possible way. However, treatment with clozapine comes with a risk of developing potentially fatal adverse reactions, for example, severe neutropenia or agranulocytosis, in which case, treatment must be discontinued. Here, we present a case of clozapine-related neutropenia that commenced after the addition of sodium valproate. A subsequent re-challenge to clozapine resulted in severe neutropenia and led to the permanent cessation of clozapine treatment. The patient had been tolerating clozapine for more than a year before the addition of sodium valproate. The awareness of an interaction between clozapine and sodium valproate could help reduce the risk of clozapine-induced neutropenia and subsequent clozapine discontinuation.

Considerations of HLA, Renal Failure, Valproic Acid Use, and Current Treatment Guidelines in Clozapine-Induced Agranulocytosis

Clozapine, the choice atypical antipsychotic for refractory schizophrenia, schizoaffective disorder, and bipolar disorder, has been shown to reduce positive and negative symptoms of schizophrenia. Clozapine, though beneficial in reducing the need for hospitalization, rehabilitation, and health care costs, is known as a drug of last resort due to its potential adverse event of clozapine-induced agranulocytosis, which holds a case fatality rate between 4.2 and 16%. Herein, we describe a female patient with longstanding schizoaffective disorder and chronic kidney disease who suffered from clozapine-induced agranulocytosis after failing two other atypical antipsychotics. Retrospective considerations of this case and management highlight risk factors such as HLA status, renal failure, and concurrent valproic acid use which presently do not have official screening, guidelines, or restrictions in place when prescribing clozapine. Additionally, there are no specific clozapine-induced agranulocytosis management recommendations such as G-CSF/filgrastim dose, timing of bone marrow aspirate and biopsy, and use of concomitant valproate. We propose that further comprehensive official screening, monitoring, and guidelines in the prescribing of clozapine, and further guidelines in the treatment of clozapine induced agranulocytosis, could increase the cost-effectiveness of clozapine treatment, and decrease the incidence, and morbidity of this feared adverse event.

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-induced agranulocytosis

Wider use of clozapine, one of the most effective antipshychotic drugs, is precluded by its propensity to cause agranulocytosis. Currently, clozapine is used for treatment-resistant schizophrenia, with mandatory blood count monitoring for the duration of treatment. Agranulocytosis occurs in up to 0.8% of patients and presents a significant medical challenge, despite decreasing mortality rates. In this paper, we review the epidemiology of clozapine-induced agranulocytosis (CLIA), advances in identifying genetic risk factors, and the preventive measures to reduce the risk of CLIA. We discuss the pathogenesis of CLIA, which, despite receiving considerable scientific attention, has not been fully elucidated. Finally, we address the clinical management and suggest the approach to clozapine re-challenge in patients with a previous episode of neutropenia. With a significant proportion of clozapine recipients in Western hemisphere being Black, we comment on the importance of recognizing benign ethnic neutropenia as a potential impediment to clozapine administration. This review aims to aid haematologists and psychiatrists to jointly manage neutropenia and agranulocytosis caused by clozapine.

Pharmacoepidemiology research: delivering evidence about drug safety and effectiveness in mental health

Research that provides an evidence base for the pharmacotherapy of people with mental disorders is needed. The abundance of digital data has facilitated pharmacoepidemiology and, in particular, observational research on the effectiveness of real-world medication. Advantages of pharmacoepidemiological research are the availability of large patient samples, and coverage of under-researched subpopulations in their naturalistic conditions. Such research is also cheaper and quicker to do than randomised controlled trials, meaning that issues regarding generic medication, stopping medication (deprescribing), and long-term outcomes are more likely to be addressed. Pharmacoepidemiological methods can also be extended to pharmacovigilance and to aid the development of new purposes for existing drugs. Drawbacks of observational pharmacoepidemiological studies come from the non-randomised nature of treatment selection, leading to confounding by indication. Potential methods for managing this drawback include active comparison groups, within-individual designs, and propensity scoring. Many of the more rigorous pharmacoepidemiology studies have been strengthened through multiple analytical approaches triangulated to improve confidence in inferred causal relationships. With developments in data resources and analytical techniques, it is encouraging that guidelines are beginning to include evidence from robust observational pharmacoepidemiological studies alongside randomised controlled trials. Collaboration between guideline writers and researchers involved in pharmacoepidemiology could help researchers to answer the questions that are important to policy makers and ensure that results are integrated into the evidence base. Further development of statistical and data science techniques, alongside public engagement and capacity building (data resources and researcher base), will be necessary to take full advantage of future opportunities.

Reduction in N-Desmethylclozapine Level Is Determined by Daily Dose But Not Serum Concentration of Valproic Acid-Indications of a Presystemic Interaction Mechanism

BACKGROUND

Valproic acid (VPA) is frequently used together with clozapine (CLZ) as mood-stabilizer or for the prevention of seizures in patients with psychotic disorders. VPA is known to reduce levels of the pharmacologically active CLZ-metabolite N-desmethylclozapine (N-DMC), but factors determining the degree of this interaction are unknown. Here, we investigated the relationship between VPA dose and serum concentration on N-DMC levels in a large patient population adjusting for sex, age, and smoking habits as covariates.

METHODS

A total of 763 patients with steady-state serum concentrations of CLZ and N-DMC concurrently using VPA (cases, n = 76) or no interacting drugs (controls, n = 687) were retrospectively included from a therapeutic drug monitoring service at Diakonhjemmet Hospital, Oslo, between March 2005 and December 2016. In addition to information about prescribed doses, age, sex, smoking habits, and use of other interacting drugs were obtained. The effects of VPA dose and serum concentration on dose-adjusted N-DMC levels were evaluated by univariate correlation and multivariate linear mixed-model analyses adjusting for covariates.

RESULTS

The dose-adjusted N-DMC levels were approximately 38% lower in VPA users (cases) versus nonusers (controls) (P < 0.001). Within the VPA cases, a negatively correlation between VPA dose and dose-adjusted N-DMC levels was observed with an estimated reduction of 1.42% per 100-mg VPA dose (P = 0.033) after adjusting for sex, age, and smoking. By contrast, there was no correlation between VPA serum concentration and dose-adjusted N-DMC levels (P = 0.873).

CONCLUSIONS

The study shows that VPA dose, not concentration, is of relevance for the degree of reduction in N-DMC level in clozapine-treated patients. Presystemic induction of UGT enzymes or efflux transporters might underlie the reduction in N-DMC level during concurrent use of VPA. Our findings indicate that a VPA daily dose of 1500 mg or higher provides a further 21% reduction in N-DMC concentration. This is likely a relevant change in the exposure of this active metabolite where low levels are associated with implications of CLZ therapy.

Evidence-based guidelines for the pharmacological treatment of schizophrenia: Updated recommendations from the British Association for Psychopharmacology

These updated guidelines from the British Association for Psychopharmacology replace the original version published in 2011. They address the scope and targets of pharmacological treatment for schizophrenia. A consensus meeting was held in 2017, involving experts in schizophrenia and its treatment. They were asked to review key areas and consider the strength of the evidence on the risk-benefit balance of pharmacological interventions and the clinical implications, with an emphasis on meta-analyses, systematic reviews and randomised controlled trials where available, plus updates on current clinical practice. The guidelines cover the pharmacological management and treatment of schizophrenia across the various stages of the illness, including first-episode, relapse prevention, and illness that has proved refractory to standard treatment. It is hoped that the practice recommendations presented will support clinical decision making for practitioners, serve as a source of information for patients and carers, and inform quality improvement.

Need to bleed? Clozapine haematological monitoring approaches a time for change

Regular haematological monitoring during clozapine treatment reduces the risk of complications and death from clozapine-related blood dyscrasias. However, many patients in the course of clozapine treatment develop neutropenia unrelated to drug treatment which leads to treatment discontinuation. The minimum haematological threshold allowed for the continuation of clozapine treatment was recently lowered in the US, but not in the UK. In this case series, we present four cases where lowering the haematological cut-off to that used in the US, allowed treatment continuation. Lowering the current UK threshold for clozapine cessation could avoid unnecessary interruptions in treatment with minimal impact on safety.

Psychiatrists' attitude towards the use of clozapine in the treatment of refractory schizophrenia: A nationwide survey

OBJECTIVES

Clozapine is the most effective treatment for refractory schizophrenia, yet it remains underused in clinical practice. The current study examined the awareness, familiarity and attitude of a nationwide sample of Israeli psychiatrists regarding the use of clozapine.

METHODS

Data were collected using questionnaires, completed by 295 psychiatrists. Participants were asked to score questions regarding clozapine procedures; familiarity with guidelines, drug properties, prescription and attitude towards specialized clozapine resources.

RESULTS

About half (53.3%) of the psychiatrists reported initiating treatment with clozapine according to the guidelines, whereas 33% reported that they administered clozapine only after three or more unsuccessful antipsychotic treatments. Surprisingly, availability of specialized resources for clozapine treatment (such as clozapine clinics) was associated with delayed initiation of clozapine treatment, and a lower rate of clozapine administration. Barriers to clozapine use included concerns about patient adherence, side effects and partial compliance with the required blood monitoring.

CONCLUSIONS

Delaying or avoiding clozapine treatment to potentially eligible patients, despite familiarity with the drug efficacy and treatment guidelines, is a major mental health concern. However, executive allocation of resources to support the use of clozapine may be ineffective in promoting clozapine use.

Clozapine, HIV and neutropenia: a case report

There is paucity of information on the use of clozapine in patients with HIV. Ethnicity, co-prescribed medications and possible drug-drug interactions are important considerations in evaluating risk of blood dyscrasias during clozapine treatment. Individuals with HIV should not be denied access to the most effective antipsychotic, but a multidisciplinary approach is essential for optimal outcome in such complex patients.

Re-titration rates after clozapine-induced neutropenia or agranulocytosis: A case report and literature review

Clozapine-induced neutropenia occurs in 3-5% of individuals treated with clozapine. Current US guidelines require interruption of clozapine when the absolute neutrophil count (ANC) drops below 1000 cells/mm3. There is minimal available guidance for what dosing schedule to use when restarting clozapine after an episode of neutropenia. Here, we present a case of a 50-year-old Caucasian female with a history of schizoaffective disorder who was successfully rechallenged on clozapine one month after developing clozapine-induced neutropenia (ANC 600 cells/mm3). To understand published re-titration rates of clozapine after neutropenia, we conducted a literature review using a using the PubMed database and found only seven case reports that unambiguously reported a clozapine dosing schedule during re-challenge. All were successful except one, a case of clozapine rechallenge after agranulocytosis. Including this case presentation, six out of eight cases restarted clozapine more cautiously than recommended by the US guidelines for a new clozapine initiation. We cannot comment what role a slower or more rapid titration plays in a successful rechallenge after neutropenia with the available evidence. We encourage researchers to publish their dosing schedule in detail after an episode of neutropenia or agranulocytosis.