Clozapine and associated QTc prolongation

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.

Genetic Biomarkers of Antipsychotic-Induced Prolongation of the QT Interval in Patients with Schizophrenia

Antipsychotics (AP) induced prolongation of the QT interval in patients with schizophrenia (Sch) is an actual interdisciplinary problem as it increases the risk of sudden death syndrome. Long QT syndrome (LQTS) as a cardiac adverse drug reaction is a multifactorial symptomatic disorder, the development of which is influenced by modifying factors (APs' dose, duration of APs therapy, APs polytherapy, and monotherapy, etc.) and non-modifying factors (genetic predisposition, gender, age, etc.). The genetic predisposition to AP-induced LQTS may be due to several causes, including causal mutations in the genes responsible for monoheme forms of LQTS, single nucleotide variants (SNVs) of the candidate genes encoding voltage-dependent ion channels expressed both in the brain and in the heart, and SNVs of candidate genes encoding key enzymes of APs metabolism. This narrative review summarizes the results of genetic studies on AP-induced LQTS and proposes a new personalized approach to assessing the risk of its development (low, moderate, high). We recommend implementation in protocols of primary diagnosis of AP-induced LQTS and medication dispensary additional observations of the risk category of patients receiving APs, deoxyribonucleic acid profiling, regular electrocardiogram monitoring, and regular therapeutic drug monitoring of the blood APs levels.

Clozapine Withdrawal-Induced Malignant Catatonia or Neuroleptic Malignant Syndrome: A Case Report and a Brief Review of the Literature

ABSTRACT

In our brief literature review, we discuss the changes in the concept of catatonia as well as its various types and symptoms. We also succinctly review the possible symptoms of clozapine withdrawal. In addition, we analyze the main features of the very few published cases of clozapine withdrawal-induced catatonia and the relationship between neuroleptic malignant syndrome and the malignant subtype of catatonia. Furthermore, we present the case of a 29-year-old male patient with schizophrenia in whom a malignant catatonic episode/neuroleptic malignant syndrome (with negativism, stupor, mutism, autonomic signs [eg, fever, hyperhidrosis], and elevated creatine kinase levels) began 5 days after the patient decided arbitrarily to cease his clozapine treatment. His catatonic symptoms quickly (ie, within a few days) resolved after the reinstitution of clozapine. Finally, we attempt to provide a theoretical explanation for the surprising finding in the literature that the withdrawal of clozapine, unlike the withdrawal of any other antipsychotics, may be associated with catatonia (frequently its malignant subtype). The take-home message of our case is that clinicians should bear in mind the risk of catatonia (especially the malignant subtype of it) after the prompt withdrawal of clozapine therapy.

Comprehensive assessment of exposure to clozapine in association with side effects among patients with treatment-resistant schizophrenia: a population pharmacokinetic study

BACKGROUND

There have been scarce data on the distribution of clozapine concentrations in comparison with the recommended range (350-600 ng/ml) or their relationship with side effects among patients with treatment-resistant schizophrenia. Furthermore, no studies have assessed the association between side effects and overall exposure to the drug by calculating the 24-h area-under-curve (AUC).

METHODS

In- and outpatients with schizophrenia or schizoaffective disorder (ICD-10) who were receiving a stable dose of clozapine for ⩾2 weeks were included. Side effects were assessed using the Glasgow antipsychotic side-effects scale for clozapine (GASS-C). Using two collected plasma samples, plasma clozapine and norclozapine concentrations at peak and trough and their 24-h AUC were estimated using population pharmacokinetic models.

RESULTS

A total of 108 patients completed the study (mean ± SD age, 43.0 ± 10.1 years; clozapine dose, 357.5 ± 136.9 mg/day); 33 patients (30.6%) showed estimated trough concentrations of clozapine within the recommended range (350-600 ng/ml) whereas the concentrations were higher and lower than this range among 37 (43.5%) and 28 (25.9%) patients (%), respectively. There were no significant correlations between estimated peak or trough concentrations or 24-h AUC of both clozapine or norclozapine, and GASS-C total or individual scores. No significant differences were found between GASS-C total or individual item scores between the patients with estimated trough concentrations of clozapine of >600 ng/ml and the other subjects.

CONCLUSION

The results suggest that clozapine or norclozapine concentrations are not linked directly to the extent of side effects experienced in clozapine-treated patients with treatment-resistant schizophrenia while the cross-sectional study design limits the interpretation of any causal relationships. These findings indicate that side effects associated with clozapine may occur at any dose or concentration.

Clozapine discontinuation withdrawal symptoms in schizophrenia

Clozapine is an atypical antipsychotic used in treatment-resistant schizophrenia. Whilst clozapine is highly effective, there are some clinical scenarios, such as the emergence of severe side effects, that necessitate its discontinuation. There is an emerging literature suggesting that discontinuing antipsychotics, in particular clozapine, can cause an array of withdrawal symptoms. We review the evidence for the existence of clozapine-induced withdrawal symptoms, and in particular focus on withdrawal-associated psychosis, cholinergic rebound, catatonia and serotonergic discontinuation symptoms. To date, there has been surprisingly little clinical guidance on how to minimise the likeliness of withdrawal symptoms in patients who are stopped on clozapine abruptly or gradually. We discuss the key outstanding questions in this area and why there is a need for guidance on the management of withdrawal symptoms associated with clozapine discontinuation.

Review of withdrawal catatonia: what does this reveal about clozapine?

Withdrawal symptoms are common upon discontinuation of psychiatric medications. Catatonia, a neuropsychiatric condition proposed to be associated with gamma-aminobutyric acid (GABA) hypoactivity due to its robust response to benzodiazepines, has been described as a withdrawal syndrome in case reports but is not a well-recognized phenomenon. The authors undertook a review of withdrawal catatonia with an aim to understand its presentation as well as the medications and psychoactive substances it is associated with. The review identified 55 cases of withdrawal catatonia, the majority of which occurred upon discontinuation of benzodiazepines (24 cases) and discontinuation of clozapine (20 cases). No other antipsychotic medications were identified as having been associated with the onset of a catatonic episode within 2 weeks following their discontinuation. Increasing GABA activity and resultant GABA receptor adaptations with prolonged use is postulated as a shared pharmacological mechanism between clozapine and benzodiazepines that underlie their association with withdrawal catatonia. The existing evidence for clozapine's activity on the GABA system is reviewed. The clinical presentations of benzodiazepine withdrawal catatonia and clozapine withdrawal catatonia appear to differ and reasons for this are explored. One reason is that benzodiazepines act directly on GABAA receptors as allosteric agonists, while clozapine has more complex and indirect interactions, primarily through effects on receptors located on GABA interneurons. Another possible reason for the difference in clinical presentation is that clozapine withdrawal catatonia may also involve receptor adaptations in non-GABA receptors such as dopamine and acetylcholine. The findings from our review have implications for the treatment of withdrawal catatonia, and treatment recommendations are provided. Further research understanding the uniqueness of clozapine withdrawal catatonia among antipsychotic medication may give some insight as to clozapine's differential mechanism of action.

Safety of antipsychotics for the treatment of schizophrenia: a focus on the adverse effects of clozapine

Clozapine, a dibenzodiazepine developed in 1961, is a multireceptorial atypical antipsychotic approved for the treatment of resistant schizophrenia. Since its introduction, it has remained the drug of choice in treatment-resistant schizophrenia, despite a wide range of adverse effects, as it is a very effective drug in everyday clinical practice. However, clozapine is not considered as a top-of-the-line treatment because it may often be difficult for some patients to tolerate as some adverse effects can be particularly bothersome (i.e. sedation, weight gain, sialorrhea etc.) and it has some other potentially dangerous and life-threatening side effects (i.e. myocarditis, seizures, agranulocytosis or granulocytopenia, gastrointestinal hypomotility etc.). As poor treatment adherence in patients with resistant schizophrenia may increase the risk of a psychotic relapse, which may further lead to impaired social and cognitive functioning, psychiatric hospitalizations and increased treatment costs, clozapine adverse effects are a common reason for discontinuing this medication. Therefore, every effort should be made to monitor and minimize these adverse effects in order to improve their early detection and management. The aim of this paper is to briefly summarize and provide an update on major clozapine adverse effects, especially focusing on those that are severe and potentially life threatening, even if most of the latter are relatively uncommon.

Antipsychotic Polypharmacy and Corrected QT Interval: A Systematic Review

OBJECTIVE

It remains unclear whether antipsychotic polypharmacy, a common clinical practice, is related to an increased risk of corrected time between start of Q wave and end of T wave (QTc) interval prolongation. We conducted a systematic review of the literature to address this important issue.

METHOD

A systematic literature search was conducted in October 2014, using MEDLINE, Embase, and PsycINFO. Studies and case reports were included if they reported QTc intervals or QTc interval changes before and after antipsychotic polypharmacy or QTc intervals in both antipsychotic polypharmacy and monotherapy groups.

RESULTS

A total of 21 articles (10 clinical trials, 4 observational studies, and 7 case reports) met inclusion criteria. The clinical trials have shown that a combination treatment with risperidone or pimozide is not obviously related to an increase in QTc interval, whereas ziprasidone or sertindole combined with clozapine may prolong QTc interval. Among the 4 observational studies, antipsychotic polypharmacy was not clearly associated with QTc prolongation in 3 studies, each cross-sectional. In contrast, one prospective study showed a significant increase in QTc interval following antipsychotic coadministration. The case reports indicated an increased risk of QTc prolongation in at least some patients receiving antipsychotic polypharmacy.

CONCLUSIONS

Currently available evidence fails to confirm that antipsychotic polypharmacy worsens QTc prolongation in general, although the evidence is scarce and inconsistent. Clinicians are advised to remain conservative in resorting to antipsychotic polypharmacy, as a combination of some QTc-prolongation liable antipsychotics may further prolong QTc interval, and efficacy supporting the clinical benefits of antipsychotic polypharmacy is equivocal, at best.

QTc interval prolongation and torsade de pointes associated with second-generation antipsychotics and antidepressants: a comprehensive review

We comprehensively reviewed published literature to determine whether it supported the link between corrected QT (QTc) interval prolongation and torsade de pointes (TdP) for the 11 second-generation antipsychotics and seven second-generation antidepressants commonly implicated in these complications. Using PubMed and EMBASE, we identified four thorough QT studies (one each for iloperidone, ziprasidone, citalopram, and escitalopram), 40 studies specifically designed to assess QTc interval prolongation or TdP, 58 publications based on data from efficacy and safety trials, 18 toxicology studies, and 102 case reports. Thorough QT studies, QTc prolongation-specific studies, and studies based on efficacy and safety trials did not link drug-associated QTc interval prolongation with TdP. They only showed that the drugs reviewed caused varying degrees of QTc interval prolongation, and even that information was not clear and consistent enough to stratify individual drugs for this risk. The few toxicology studies provided valuable information but their findings are pertinent only to situations of drug overdose. Case reports were most informative about the drug-QTc interval prolongation-TdP link. At least one additional well established risk factor for QTc prolongation was present in 92.2 % of case reports. Of the 28 cases of TdP, six (21.4 %) experienced it with QTc interval <500 ms; 75 % of TdP cases occurred at therapeutic doses. There is little evidence that drug-associated QTc interval prolongation by itself is sufficient to predict TdP. Future research needs to improve its precision and broaden its scope to better understand the factors that facilitate or attenuate progression of drug-associated QTc interval prolongation to TdP.

A review of the use of clozapine levels to guide treatment and determine cause of death

OBJECTIVE

To review the literature to examine the use of clozapine levels to (i) guide therapy and prevent toxicity in clinical care and (ii) determine cause of death in post-mortem examination of patients who were treated with clozapine.

METHODS

MEDLINE was searched in December 2010 using the following keywords: 'clozapine levels', 'clozapine and toxicity', 'clozapine and death', 'clozapine and mortality' and 'post-mortem redistribution'. Data was also collected from the 2010 MIMS Annual.

RESULTS

The literature reported significant variation in clozapine levels attained with any given dose, and considerable variability in the clinical response achieved at any given clozapine level. The lowest effective clozapine levels ranged from 250 to 550 µg/L, while the recommended upper limit to prevent toxicity varied from 600 to 2000 µg/L. There was minimal correlation between clozapine levels and side effects, with the exception of sedation, hypotension and seizure activity. The risk of seizures increased with plasma clozapine levels greater than 600 µg/L or rapid upward titration. In addition to prescribed dose, there are many factors that influence plasma clozapine levels. After death, the process of post-mortem drug redistribution resulted in 3.00 to 4.89 times increases in clozapine levels in central blood vessels and 1.5 fold increases in peripheral vessels compared to ante-mortem levels.

CONCLUSIONS

The exact range of clozapine levels that corresponds to toxicity remains unclear. However, levels between 350 µg/L and 1000 µg/L achieved with gradual upward titration are more likely to be effective and less likely to cause toxicity. Ongoing clozapine level monitoring is indicated, especially when (i) prescribing higher doses (> 600 mg/day) of clozapine, (ii) there has been a change in a patient's concomitant pharmacotherapy or cigarette use and (iii) there has been a suboptimal response to treatment. The use of post-mortem clozapine levels to determine clozapine toxicity as a cause of death is unreliable.