Clozapine-induced myocarditis: Follow-up for 3.5 years after successful retrial

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.

Patterns of C-reactive protein trends during clozapine titration and the onset of clozapine-induced inflammation: a case series of weekly and daily C-reactive protein monitoring

Background

International guidelines for clozapine titration recommend measuring C-reactive protein (CRP) weekly for 4 weeks after clozapine initiation to prevent fatal inflammatory adverse events, including myocarditis. However, limited evidence exists regarding whether weekly CRP monitoring can prevent clozapine-induced inflammation.

Aims

We examined the relationship between CRP trends and the development of clozapine-induced inflammation. We also explored the usefulness and limitations of CRP monitoring during clozapine titration.

Method

This study presents 17 and 4 cases of weekly and daily CRP monitoring during clozapine initiation, respectively.

Results

Among 17 patients with weekly CRP measurements, 7 had fever. Elevated CRP levels were detected before the onset of fever in two of the seven patients. Of the five remaining patients, the CRP levels on a previous test had been low; however, the fever developed suddenly. Of the 10 patients with no fever under weekly CRP monitoring, three had elevated CRP levels >3.0 mg/dL. Refraining from increasing the clozapine dose may have prevented fever in these patients. Among four patients with daily CRP measurements, two became febrile. In both cases, CRP levels increased almost simultaneously with the onset of fever.

Conclusion

Weekly and daily CRP monitoring during clozapine titration is valuable for preventing clozapine-induced inflammation, assessing its severity, and guiding clozapine dose adjustments. Weekly CRP monitoring may not adequately predict clozapine-induced inflammation in some cases. Consequently, clinicians should be aware of the sudden onset of clozapine-induced inflammation, even if CRP levels are low. Daily CRP monitoring is better for detecting clozapine-induced inflammation.

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.

Using therapeutic drug monitoring to personalize clozapine dosing in Asians

This narrative review on clozapine blood levels or therapeutic drug monitoring (TDM) includes sections focused on drug clearance and TDM, personalized dosing with TDM, clinical applications of TDM in Asians, and areas needing further study. Asian patients need half the clozapine dose (D) used in the United States to get the same blood concentrations (C). The concentration-to-dose (C/D) ratio measures drug clearance. In the United States, the average clozapine patient usually needs from 300 to 600 mg/day to reach 350 ng/mL. US male smokers reach this therapeutic C with a D of 600 mg/day (C/D ratio of 0.60 = 600/350), whereas US female nonsmokers usually need a D of 300 mg/day (C/D ratio of 1.17 = 300/350). While in the United States, average CLO C/D ratios typically are 0.6-1.2 ng/mL per mg/day, in Asian populations they range from 1.20 in male smokers to 2.40 in female smokers, requiring Ds of 300 to 150 mg/day to obtain 350 ng/mL. Asian patients can become clozapine poor metabolizers (PMs), needing very low Ds (50-150 mg/day) to get therapeutic Cs, by taking inhibitors (fluvoxamine, oral contraceptives and valproic acid), due to obesity, or during inflammations with systemic effects. In 573 Asian patients from five samples, around 1% were PMs due to taking inhibitors, 1% due to inflammation, 1% due to obesity, and 7% were potential genetic PMs. The potential genetic PMs ranged between 3% and 13%, but this prevalence will have to be better established in future studies including genetic testing for possible CYP1A2 mutations, which may explain PM status.

A case report on clozapine-induced ventricular ectopics: a fatal adverse drug reaction

Background Clozapine is one of the most efficacious antipsychotic drug used for the treatment-resistant schizophrenia; it is sometimes associated with serious adverse reactions like agranulocytosis, myocarditis, cardiac rhythm disturbances, etc. Case presentation A 30-year-old patient with a primary diagnosis of paranoid schizophrenia (ICD code - F20.05) was on regular prescription for 6 years. Due to refractoriness, the patient was initiated on tablet clozapine. After 45 days of clozapine therapy, he presented with the complaints of worsening of positive symptoms and sudden falls associated with a brief period of unresponsiveness for which the patient was admitted for evaluation. After stabilization of the patient, it was concluded that he was suffering from ventricular ectopics based upon cardiac investigations like electrocardiogram (ECG) and Holter monitoring. Upon causality assessment between the adverse drug reaction (ADR) and the suspected drug using Naranjo Scale and WHO causality assessment scale, the ADR was found to be probable. Conclusions This case report will help to keep physicians vigilant about the rare cardiac side effects of clozapine and to do regular ECG monitoring of the patients who are on clozapine. Moreover, this case report generates the evidence of clozapine-induced arrhythmia, which is needed to be quantified with aggressive study design and there is a need to study the dose-dependent relationship of clozapine-induced arrhythmia.

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.