A dose-dependent relationship between quetiapine and QTc interval

Impact of quetiapine on ion channels and contractile dynamics in rat ventricular myocyte

Antipsychotic drugs often lead to adverse effects, including those related to the cardiovascular system. Of these, quetiapine is known to cause significant changes in the QT interval although the underlying mechanism remains mysterious, prompting us to examine its effects on cardiac electrophysiological properties. Therefore, we investigated the effect of quetiapine on contraction, action potential (AP), and the associated membrane currents such as L-type Ca2+ and K+ using the whole-cell patch clamp method to examine its impacts on isolated rat ventricular myocytes. Our results showed that (1) quetiapine reduces cell contractility in a concentration-dependent manner and (2) leads to a significant prolongation in the duration of AP in isolated ventricular myocytes. This effect was both concentration and frequency-dependent; (3) quetiapine significantly decreased the Ca2+, transient outward K+, and steady-state K+ currents. However, only high concentration of quetiapine (100 μM) could significantly change the activation and reactivation kinetics of L-type Ca2+ channels. This study demonstrates that QT extension induced by quetiapine is mainly associated with the prolongation of AP. Moreover, quetiapine caused a significant decrease in contractile force and excitability of ventricular myocytes by suppressing Ca2+ and K+ currents.

A Case of Sudden Cardiac Arrest

Editor's note: This is the next installment in a series on electrocardiogram (ECG) interpretation. Nurses in all settings should know the basics, as medications and physiological changes can cause cardiac arrhythmias. Each article will start with a brief case scenario and an ECG strip and then take you step by step through analyzing the heart rhythm.

Quetiapine induces myocardial necroptotic cell death through bidirectional regulation of cannabinoid receptors

Quetiapine is a common atypical antipsychotic used to treat mental disorders such as schizophrenia, bipolar disorder, and major depressive disorder. There has been increasing number of reports describing its cardiotoxicity. However, the molecular mechanisms underlying quetiapine-induced myocardial injury remain largely unknown. Herein, we reported a novel cell death type, quetiapine-induced necroptosis, which accounted for quetiapine cardiotoxicity in mice and proposed novel therapeutic strategies. Quetiapine-treated hearts showed inflammatory infiltration and evident fibrosis after 21-day continuous injection. The specific increases of protein levels of RIP3, MLKL and the phosphorylation of MLKL showed that quetiapine induced necroptotic cell death both in vivo and in vitro. Pharmacologic blockade of necroptosis using its specific inhibitor Necrostatin-1 attenuated quetiapine-induced myocardial injury in mice. In addition, quetiapine imbalanced the endocannabinoid system and caused opposing effects on two cannabinoid receptors (CB1R and CB2R). Specific antagonists of CB1R (AM 281, Rimonabant), but not its agonist ACEA significantly ameliorated the heart histopathology induced by chronic quetiapine exposure. By contrast, specific agonists of CB2R (JWH-133, AM 1241), but not its antagonist AM 630 exerted beneficial roles against quetiapine cardiotoxicity. The protective agents (AM 281, Rimonabant, AM 1241, and JWH-133) consistently inactivated the quetiapine-induced necroptosis signaling. Quetiapine bidirectionally regulates cannabinoid receptors and induces myocardial necroptosis, leading to cardiac toxic effects. Therefore, pharmacologic inhibition of CB1R or activation of CB2R represents promising therapeutic strategies against quetiapine-induced cardiotoxicity.

QTc prolongation in short-term treatment of schizophrenia patients: effects of different antipsychotics and genetic factors

Antipsychotics are effective in treating schizophrenia but may lead to a higher cardiovascular risk due to QTc prolongation. Besides drugs, genetic and clinical factors may contribute to QTc prolongation. The aim of this study is to examine the effect of candidate genes known for QTc prolongation and their interaction with common antipsychotics. Thus, 199 patients were genotyped for nine polymorphisms in KCNQ1, KCNH2, SCN5A, LOC10537879, LOC101927066, NOS1AP and NUBPL. QTc interval duration was measured before treatment and weekly for 5 weeks while being treated with risperidone, quetiapine, olanzapine, amisulpride, aripiprazole and haloperidol in monotherapy. Antipsychotics used in this study showed a different potential to affect the QTc interval. We found no association between KCNH2, KCNQ1, LOC10537879, LOC101927066, NOS1AP and NUBPL polymorphisms and QTc duration at baseline and during antipsychotic treatment. Mixed general models showed a significant overall influence of SCN5A (H558R) on QTc duration but no significant interaction with antipsychotic treatment. Our results do not provide evidence for an involvement of candidate genes for QTc duration in the pathophysiology of QTc prolongation by antipsychotics during short-term treatment. Further association studies are needed to confirm our findings. With a better understanding of these interactions the cardiovascular risk of patients may be decreased.