Clozapine-Associated Obsessive-Compulsive Symptoms and Their Management: A Systematic Review and Analysis of 107 Reported Cases

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.

Review of Management Considerations for Excoriation Disorder in Older Adults

Excoriation disorder (ED) is defined as compulsive skin picking that results in skin damage and emotional distress. Optimal management of ED includes individualized treatment plans consisting of psychotherapies, behavioral and pharmacologic interventions. Compared with younger populations, older adults are at increased risk for poor outcomes, such as infection and hospitalization, and require unique management considerations. Risk factors that contribute to disease burden include age-related changes to the skin and underlying medical and psychiatric comorbidities. A literature review was conducted on ED yielding limited evidence exclusive to older adults. The authors suggest a therapeutic approach to ED in older adults based on available evidence and experience from inpatient and outpatient psychiatric settings. Finally, opportunities for future research are highlighted.

Optimizing antidepressant and clozapine co-prescription in clinical practice: A systematic review and expert recommendations

OBJECTIVES

To synthesize the information relevant for clinical practice on clozapine-antidepressant co-prescription concerning pharmacokinetic drug-drug interactions (DDI), adverse drug reactions (ADRs) associated with the co-prescription, antidepressant add-on for clozapine-resistant symptoms and antidepressant add-on for clozapine-induced ADRs.

METHODS

Articles were identified with MEDLINE, Web of Sciences and PsycINFO search from inception through April 2023. Data were synthesized narratively.

RESULTS

ADRs are most often induced by the co-prescription of antidepressants that inhibit CYP enzymes (fluvoxamine, fluoxetine, paroxetine). Fluvoxamine add-on is hazardous because of its potent inhibition of clozapine metabolism and has few indications (lowering daily number of clozapine tablets, reducing norclozapine-induced metabolic disturbances and other dose-dependent clozapine-induced ADRs). ADR frequency may be reduced by therapeutic drug monitoring and knowledge of other factors impacting clozapine metabolism (pneumonia, inflammation, smoking, etc.). Improvement of negative symptoms is the most documented beneficial effect of antidepressant add-on for clozapine-resistant psychotic symptoms. The add-on antidepressant should be chosen according to its safety profile regarding DDI with clozapine: antidepressants inhibiting clozapine metabolism or increasing the anticholinergic load should be avoided. Other indications of antidepressant add-on (affective or obsessive compulsive symptoms, sialorrhea, and enuresis) are poorly documented.

CONCLUSION

Antidepressant add-on to clozapine is associated with potential benefits in clozapine users as this strategy may contribute to reduce the burden of clozapine-resistant symptoms or of clozapine-induced ADRs. Further studies are needed to determine whether antidepressant add-on can reduce the risk of clozapine discontinuation.

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.

Obsessive-compulsive symptoms and disorder in clozapine-treated schizophrenia

BACKGROUND

Obsessive-compulsive symptoms (OCS) and obsessive-compulsive disorder (OCD) are commonly reported in patients with schizophrenia. Furthermore, the use of clozapine in treatment-resistant schizophrenia has been thought to induce or aggravate these disorders. To date, there is a paucity of research regarding the prevalence and associated factors. Hence, this study aims to report the prevalence of OCS and OCD, and examine potential risk factors, in clozapine-treated schizophrenia.

METHODS

This is a cross-sectional study conducted in the only tertiary hospital for psychiatric patients in Singapore. In total, 162 patients on a stable dose of clozapine were recruited for this study; 159 patients with a diagnosis of schizophrenia or schizoaffective disorder were included in the current analysis. Sociodemographic, clinical and treatment factors were analysed to identify factors associated with OCS and OCD.

RESULTS

The prevalence of OCS and OCD is 21.4% and 12.6% respectively. Factors associated with OCS include younger age (OR:0.96, p=0.033) and younger age of onset of psychosis (OR:0.92, p=0.017). There were no significant factors associated with OCD. However, in an analysis of both OCS and/or OCD, factors associated include younger age (OR:0.96, p=0.027) and younger age of onset of psychosis (OR:0.91, p=0.016). Severity of psychotic illness and Clozapine dose were not associated with OCS or OCD in clozapine-treated schizophrenia.

DISCUSSION & CONCLUSIONS

Our results suggest a high prevalence of OCS and OCD in clozapine-treated schizophrenia which clinicians should routinely screen for. Further research is warranted to establish the link between the factors identified in this study and OCS/OCD in clozapine-treated schizophrenia.

The Neurobiological Underpinnings of Obsessive-Compulsive Symptoms in Psychosis, Translational Issues for Treatment-Resistant Schizophrenia

Almost 25% of schizophrenia patients suffer from obsessive-compulsive symptoms (OCS) considered a transdiagnostic clinical continuum. The presence of symptoms pertaining to both schizophrenia and obsessive-compulsive disorder (OCD) may complicate pharmacological treatment and could contribute to lack or poor response to the therapy. Despite the clinical relevance, no reviews have been recently published on the possible neurobiological underpinnings of this comorbidity, which is still unclear. An integrative view exploring this topic should take into account the following aspects: (i) the implication for glutamate, dopamine, and serotonin neurotransmission as demonstrated by genetic findings; (ii) the growing neuroimaging evidence of the common brain regions and dysfunctional circuits involved in both diseases; (iii) the pharmacological modulation of dopaminergic, serotoninergic, and glutamatergic systems as current therapeutic strategies in schizophrenia OCS; (iv) the recent discovery of midbrain dopamine neurons and dopamine D1- and D2-like receptors as orchestrating hubs in repetitive and psychotic behaviors; (v) the contribution of N-methyl-D-aspartate receptor subunits to both psychosis and OCD neurobiology. Finally, we discuss the potential role of the postsynaptic density as a structural and functional hub for multiple molecular signaling both in schizophrenia and OCD pathophysiology.

Obsessive-compulsive symptoms in the schizophrenia-spectrum: current developments in psychopathology research

PURPOSE OF REVIEW

Schizophrenia-spectrum disorders (SSD) frequently involve symptoms that usually are ascribed to nonpsychotic disorder spectra, such as obsessive-compulsive symptoms (OCS). These symptoms can cause differential diagnostic challenges, particularly in early illness stages, and must be considered in treatment planning. In this review, we provide an overview of recent literature within the field of OCS in SSD, with a focus on psychopathology research.

RECENT FINDINGS

OCS are seen in approximately a quarter of patients with SSD or at-risk mental state of psychosis. They are associated with more severe clinical features and specific temporal patterns of OCS may be linked with different clinical trajectories. However, the current definitions of OCS have been criticized for their overinclusive nature, which is a limiting step for differential diagnosis and more precise prognostic stratification. Specific phenomenological features, including a link with experiential anomalies (disorders of basic self), have been suggested to provide clinically relevant distinctions.

SUMMARY

The presence of OCS in SSD is associated with more severe clinical features and invites a higher clinical attention and perspectival monitoring. Some findings suggest that more fine-grained psychopathological distinctions might be a viable clinical and research strategy to advance the field in the direction of precision psychiatry.

Disclosing common biological signatures and predicting new therapeutic targets in schizophrenia and obsessive-compulsive disorder by integrated bioinformatics analysis

Schizophrenia (SCZ) is a severe mental illness mainly characterized by a number of psychiatric symptoms. Obsessive-compulsive disorder (OCD) is a long-lasting and devastating mental disorder. SCZ has high co-occurrence with OCD resulting in the emergence of a concept entitled "schizo-obsessive disorder" as a new specific clinical entity with more severe psychiatric symptoms. Many studies have been done on SCZ and OCD, but the common pathogenesis between them is not clear yet. Therefore, this study aimed to identify shared genetic basis, potential biomarkers and therapeutic targets between these two disorders. Gene sets were extracted from the Geneweaver and Harmonizome databases for each disorder. Interestingly, the combination of both sets revealed 89 common genes between SCZ and OCD, the most important of which were BDNF, SLC6A4, GAD1, HTR2A, GRIN2B, DRD2, SLC6A3, COMT, TH and DLG4. Then, we conducted a comprehensive bioinformatics analysis of the common genes. Receptor activity as the molecular functions, neuron projection and synapse as the cellular components as well as serotonergic synapse, dopaminergic synapse and alcoholism as the pathways were the most significant commonalities in enrichment analyses. In addition, transcription factor (TFs) analysis predicted significant TFs such as HMGA1, MAPK14, HINFP and TEAD2. Hsa-miR-3121-3p and hsa-miR-495-3p were the most important microRNAs (miRNAs) associated with both disorders. Finally, our study predicted 19 existing drugs (importantly, Haloperidol, Fluoxetine and Melatonin) that may have a potential influence on this co-occurrence. To summarize, this study may help us to better understand and handle the co-occurrence of SCZ and OCD by identifying potential biomarkers and therapeutic targets.

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.

A diffusion tensor imaging study in schizophrenia patients with clozapine induced obsessive compulsive symptoms

OBJECTIVE

The aim of this study was to evaluate brain connectivity by diffusion tensor imaging (DTI) in schizophrenia patients with clozapine-induced obsessive compulsive symptoms (OCS).

METHODS

Eighteen schizophrenia patients, nine of which had clozapine-induced OCS (Clz-OCS (+)), 9 without OCS (Clz-OCS (-)) and 9 healthy controls were included. Psychopathology was evaluated with Positive and Negative Syndrome Scale and Yale-Brown Obsession and Compulsion Scale in the patient groups. All groups were assesed with neurocognitive tests and DTI.

RESULTS

Tract-Based Spatial Statistics based comparison of DTI revealed lower fractional anisotropy in the genu of corpus callosum (CC), right cingulum, left frontal white matter (WM) in the Clz-OCS (+) group, compared to controls. Fractional anisotropy was found to be lower in the bilateral occipital WM and higher in the bilateral medial temporal regions, anterior limb of internal capsule, cingulum, frontoparietal peripheral WM, right external capsule and genu of CC in Clz-OCS (+) patients compared to Clz-OCS (-).

CONCLUSIONS

WM integrity in several pathways such as cortico-striato-thalamo-cortical circuitry and orbito-frontal tracts seems to be affected differently in patients with Clz-OCS (+). Different neuroplastic effects of clozapine leading to occurrence of OCS in a subgroup of patients is possible, and needs further evaluation by longitudinal follow-up studies.

Suicidal Ideation and Obsessive-Compulsive Disorder: Links and Knowledge

Suicidal ideation (SI) is understudied in obsessive-compulsive disorder (OCD). Nonetheless, evidence suggests increased risk for SI in individuals with OCD compared to the general population. Understanding the relationship between SI and OCD involves investigating risk factors associated with SI. Furthering knowledge of links is essential for enhancing outcomes and decreasing experiences of SI through improving treatment interventions. Additionally, increasing awareness of factors that lead SI to suicide attempts (SA) is vital. To best illustrate the current state of knowledge, this scoping review examines risk factors for SI, including symptom profiles or phenotypes, comorbid diagnoses, sociodemographic and lifestyle factors, childhood trauma, and genetic and familial contributions. Important treatment considerations for targeting SI within the context of OCD are detailed with respect to the current evidence for psychotherapy, pharmacology, brain stimulation, and neurosurgery. Gaps in the literature and future directions are identified, broadly with respect to studies examining the treatment of SI within the context of OCD, particular OCD phenotypes, and factors influencing SI in pediatric OCD. Due to the relative novelty of this area of exploration, many unknowns persist regarding onset of SI in OCD, factors contributing to the maintenance of SI in OCD, and relevant treatment protocols. Findings suggest that individuals with previous SI or SA, history of childhood trauma, significant life stress, and psychiatric comorbidities, particularly depression, should be closely monitored and screened for SI.

[Obsessive-compulsive symptoms in psychotic disorders: pathogenesis and treatment]

BACKGROUND

Comorbid disorders often occur in psychoses from the schizophrenia spectrum and are an additional burden for patients' quality of life, render treatment and rehabilitation prognosis more difficult and can also contribute to suicidal ideation. Specifically, obsessive-compulsive syndrome (OCS) and OC disorder (OCD) have been reported.

OBJECTIVE

What is known about the epidemiology and pathogenesis and which conclusions can be drawn regarding the diagnostics and treatment?

MATERIAL AND METHODS

This review evaluated current reports on comorbid OCS during different stages of psychotic disorders, starting with the at-risk mental state (ARMS) via the first manifestation and up to chronic courses. The focus was on pharmacological and psychotherapeutic consequences.

RESULTS

Patients with ARMS suffer much more often from OCS than the general population. The prevalence is even higher in patients with a first manifestation of psychosis. During the chronic courses ca. 30% of patients are affected by comorbid OCS and 12% fulfill the diagnostic criteria of a OCD. The pathogenesis can most likely be explained by a genetic disposition in the glutamatergic system, shared structural and functional abnormalities of cortical and subcortical structures, pharmacological influences and psychosocial stressors.

CONCLUSION

Clozapine and other antipsychotics may induce or aggravate OCS in a dose-dependent manner. In order to alleviate symptoms clozapine should be reduced to a minimally sufficient level. This can be attempted through combination, for example with dopaminergic antipsychotics. In general, serotonergic antidepressants can be added. Cognitive behavioral therapy should be offered to every patient with comorbid OCS. For future research multimodal longitudinal studies investigating the efficacy of interventions and aimed at the subjective level will be important.

Obsessive Thought, Compulsive Behavior, and Their Associations With Suicide Ideation and Attempts and Major Depressive Disorder: A Nationwide Community Sample of Korean Adults

ABSTRACT

In this study, we defined obsessive thoughts (OT) as bothersome, unpleasant thoughts about oneself that keep entering the mind against one's will, and compulsive behavior (CB) as behavior that a person repeats against his or her wishes. The study included 12,532 adults selected randomly through a one-person-per-household method. Each subject selected underwent a face-to-face interview using the Korean version of the Composite International Diagnostic Interview with a questionnaire that examines lifetime suicide attempts (LSAs). Among the participants, 341 (2.74%) had OT and 639 (5.14%) had CB. The highest LSA rate was in subjects with both OT and CB, followed by those with either OT or CB; subjects with neither OT nor CB had the lowest LSA rate. In a multivariate logistic regression analysis of OT and CB, OT, ordering, and rituals of repeating words were significantly associated with LSAs. In subjects with OT and CB, those with MDD had a significantly higher risk of LSAs compared with those without, and MDD with both OT and CB showed odds of approximately 27-fold (adjusted odds ratio, 27.24; 13.29-55.82; p < 0.0001) compared with those without MDD, OT, or CB. OT and CB were associated with increased risk of LSAs, and comorbid MDD further increased LSAs.

Clozapine: Why Is It So Uniquely Effective in the Treatment of a Range of Neuropsychiatric Disorders?

Clozapine is superior to other antipsychotics as a therapy for treatment-resistant schizophrenia and schizoaffective disorder with increased risk of suicidal behavior. This drug has also been used in the off-label treatment of bipolar disorder, major depressive disorder (MDD), and Parkinson's disease (PD). Although usually reserved for severe and treatment-refractory cases, it is interesting that electroconvulsive therapy (ECT) has also been used in the treatment of these psychiatric disorders, suggesting some common or related mechanisms. A literature review on the applications of clozapine and electroconvulsive therapy (ECT) to the disorders mentioned above was undertaken, and this narrative review was prepared. Although both treatments have multiple actions, evidence to date suggests that the ability to elicit epileptiform activity and alter EEG activity, to increase neuroplasticity and elevate brain levels of neurotrophic factors, to affect imbalances in the relationship between glutamate and γ-aminobutyric acid (GABA), and to reduce inflammation through effects on neuron-glia interactions are common underlying mechanisms of these two treatments. This evidence may explain why clozapine is effective in a range of neuropsychiatric disorders. Future increased investigations into epigenetic and connectomic changes produced by clozapine and ECT should provide valuable information about these two treatments and the disorders they are used to treat.

Efficacy and tolerability of aripiprazole versus D2 antagonists in the early course of schizophrenia: a systematic review and meta-analysis

Early intervention is essential for favorable long-term outcomes in schizophrenia. However, there is limited guidance in the scientific literature on how best to choose between dopamine D₂ receptor (D₂R) partial agonists and D₂R antagonists in early stages of schizophrenia. The aim of this meta-analysis was to directly compare D₂R partial agonists with D₂R antagonists for efficacy and tolerability, using randomized controlled trials (RCTs) that involved participants diagnosed with first-episode psychosis, schizophrenia, or related psychotic disorders with a duration of illness ≤5 years. Fourteen RCTs, involving 2494 patients, were included in the meta-analysis. Aripiprazole was the only identified D₂R partial agonist, and was not significantly different from pooled D₂R antagonists for overall symptom reduction or all-cause discontinuation. However, aripiprazole was more favorable than pooled D₂R antagonists for depressive symptoms, prolactin levels, and triglyceride levels. Specifically, aripiprazole was more favorable than paliperidone for triglyceride levels and more favorable than risperidone and olanzapine, but less favorable than ziprasidone, for weight gain. In addition, aripiprazole was less favorable for akathisia compared with second-generation D₂R antagonists, in particular olanzapine and quetiapine, and less favorable for discontinuation due to inefficacy than risperidone. Lastly, aripiprazole was more favorable than haloperidol for various efficacy and tolerability outcomes. In conclusion, aripiprazole’s efficacy did not differ substantially from D₂R antagonists in the early course of schizophrenia, whereas differential tolerability profiles were noted. More double-blind RCTs are required comparing the efficacy and tolerability of aripiprazole as well as other D₂R partial agonists with D₂R antagonists in early stages of schizophrenia.

Clozapine-induced gastroesophageal rumination in 22q11.2 Deletion Syndrome. A case report on gastroesophageal side effects management without renouncing clozapine's effectiveness

Despite entailing more severe and uncommon side effects in 22q11.2DS compared to idiopathic schizophrenia, we strongly believe that clozapine should continue to be considered the gold standard for all treatment-resistant schizophrenia, even in 22qDS.

Clinical risk factors, phenomenology and the impact of clozapine induced obsessive compulsive symptoms

The aim of this study was to investigate the clinical risk factors, phenomenology and the impact of clozapine induced obsessive-compulsive symptoms (OCS) in patients with schizophrenia. One hundred twenty-two patients receiving clozapine treatment for at least 6 weeks were assessed with Structured Clinical Interview for Axis-I Disorders for DSM-IV, Positive and Negative Syndrome Scale, Yale-Brown Obsessive Compulsive Scale and Checklist, Calgary Depression Scale, Clinical Global Impression Scale and WHO-Disability Assessment Schedule-II. Information about past and current clinical status were gathered through clinical interviews and medical records. With clozapine 44.3% of the patients had de novo OCS, 33.6% had OCS both before and after clozapine, 21.3% didn't report any OCS. Clozapine doses, clozapine and norclozapine plasma levels were not significantly different. Severity of OCS was affected by clozapine and norclozapine plasma levels, and correlated with increased disability. Obsessions were less in clozapine induced OCS group, and compulsions, especially of checking subtypes, were predominant, compared to the group with prior history of OCS, who reported a significant increase in checking compulsion after clozapine treatment. Clozapine induced OCS should be considered during cost/benefit assessment of clozapine treatment, and understanding the risk factors and its different phenomenology may shed light into the underlying mechanisms.

Relationship between clozapine dose and severity of obsessive-compulsive symptoms

Evidence supports the fact that clozapine can induce stressful obsessive-compulsive symptoms (OCS). Although clozapine's robust inhibition of serotonergic neurotransmission is believed to be a key mechanism underlying clozapine-induced OCS, the exact mechanism(s) are not fully understood. Intuitively, it is reasonable to believe that the dose of clozapine is likely related to emergent OCS severity. However, there is conflicting evidence where both positive and inverse relationships have been demonstrated between clozapine dose and emergent OCS severity. Upon examination of clozapine's receptor profile, in particular its affinity for 5-HT_2A and D₂ receptors, we hypothesize that there is a biphasic relationship between clozapine dose and emergent OCS severity. We present here a preliminary analysis of published cases in the literature to support our hypothesis.

A Focused Review of the Metabolic Side-Effects of Clozapine

The second generation antipsychotic drug clozapine represents the most effective pharmacotherapy for treatment-resistant psychosis. It is also associated with low rates of extrapyramidal symptoms and hyperprolactinemia compared to other antipsychotic drugs. However, clozapine tends to be underutilized in clinical practice due to a number of disabling and serious side-effects. These are characterized by a constellation of metabolic side-effects which include dysregulation of glucose, insulin, plasma lipids and body fat. Many patients treated with clozapine go on to develop metabolic syndrome at a higher rate than the general population, which predisposes them for Type 2 diabetes mellitus and cardiovascular disease. Treatments for the metabolic side-effects of clozapine vary in their efficacy. There is also a lack of knowledge about the underlying physiology of how clozapine exerts its metabolic effects in humans. In the current review, we focus on key studies which describe how clozapine affects each of the main symptoms of the metabolic syndrome, and cover some of the treatment options. The clinical data are then discussed in the context of preclinical studies that have been conducted to identify the key biological substrates involved, in order to provide a better integrated overview. Suggestions are provided about key areas for future research to better understand how clozapine causes metabolic dysregulation.

A Rational Use of Clozapine Based on Adverse Drug Reactions, Pharmacokinetics, and Clinical Pharmacopsychology

Using Richardson and Davidson's model and the sciences of pharmacokinetics and clinical pharmacopsychology, this article reviewed the: (1) poor life expectancy associated with treatment-resistant schizophrenia (TRS), which may be improved in patients who adhere to clozapine; (2) findings that clozapine is the best treatment for TRS (according to efficacy, effectiveness and well-being); and (3) potential for clozapine to cause vulnerabilities, including potentially lethal adverse drug reactions such as agranulocytosis, pneumonia, and myocarditis. Rational use requires: (1) modification of the clozapine package insert worldwide to include lower doses for Asians and to avoid the lethality associated with pneumonia, (2) the use of clozapine levels for personalizing dosing, and (3) the use of slow and personalized titration. This may make clozapine as safe as possible and contribute to increased life expectancy and well-being. In the absence of data on COVID-19 in clozapine patients, clozapine possibly impairs immunological mechanisms and may increase pneumonia risk in infected patients. Psychiatrists should call their clozapine patients and families and explain to them that if the patient develops fever or flu-like symptoms, the psychiatrist should be called and should consider halving the clozapine dose. If the patient is hospitalized with pneumonia, the treating physician needs to assess for symptoms of clozapine intoxication since halving the dose may not be enough for all patients; consider decreasing it to one-third or even stopping it. Once the signs of inflammation and fever have disappeared, the clozapine dose can be slowly increased to the prior dosage level.