Risk of QT prolongation and torsade de pointes associated with exposure to hydroxyzine: re-evaluation of an established drug

Several noncardiac drugs have been linked to cardiac safety concerns, highlighting the importance of post‐marketing surveillance and continued evaluation of the benefit‐risk of long‐established drugs. Here, we examine the risk of QT prolongation and/or torsade de pointes (TdP) associated with the use of hydroxyzine, a first generation sedating antihistamine. We have used a combined methodological approach to re‐evaluate the cardiac safety profile of hydroxyzine, including: (1) a full review of the sponsor pharmacovigilance safety database to examine real‐world data on the risk of QT prolongation and/or TdP associated with hydroxyzine use and (2) nonclinical electrophysiological studies to examine concentration‐dependent effects of hydroxyzine on a range of human cardiac ion channels. Based on a review of pharmacovigilance data between 14th December 1955 and 1st August 2016, we identified 59 reports of QT prolongation and/or TdP potentially linked to hydroxyzine use. Aside from intentional overdose, all cases involved underlying medical conditions or concomitant medications that constituted at least 1 additional risk factor for such events. The combination of cardiovascular disorders plus concomitant treatment of drugs known to induce arrhythmia was identified as the greatest combined risk factor. Parallel patch‐clamp studies demonstrated hydroxyzine concentration‐dependent inhibition of several human cardiac ion channels, including the ether‐a‐go‐go‐related gene (hERG) potassium ion channels. Results from this analysis support the listing of hydroxyzine as a drug with “conditional risk of TdP” and are in line with recommendations to limit hydroxyzine use in patients with known underlying risk factors for QT prolongation and/or TdP.

Effect of FiO2 in the measurement of VO2 and VCO2 using the E-COXV metabolic monitor

OBJECTIVE

We evaluated the effect of changes in FiO₂ on the bias and accuracy of the determination of oxygen consumption (V˙O₂) and carbon dioxide production (V˙CO₂) using the E-COVX monitor in patients with mechanical ventilation.

DESIGN

Descriptive of concordance.

SETTING

Intensive Care Unit.

PATIENTS OR PARTICIPANTS

Patients with mechanical ventilation.

INTERVENTIONS

We measured V˙O₂ and V˙CO₂ using the E-COVX monitor. Values recorded were the average in 5min. Two groups of 30 patients. We analyzed: 1) the reproducibility in the measurement of V˙O₂ and V˙CO₂ at FiO₂ 0.4, and 2) the effect of the changes in FiO₂ on the measurement of V˙O₂ and V˙CO₂. Statistical analysis was performed using Bland and Altman test.

VARIABLES OF MAIN INTEREST

Bias and accuracy.

RESULTS

1) FiO₂ 0.4 reproducibility: The bias in the measurement of V˙O₂ and V˙CO₂ was 1.6 and 2.1mL/min, respectively, and accuracy was 9.7 to -8.3% and 7.2 to -5.2%, respectively, and 2) effect of FiO₂ on V˙O₂: The bias of V˙O₂ measured at FiO₂ 0.4 and 0.6 was -4.0mL/min and FiO₂ 0.4 and 0.8 was 5.2mL/min. Accuracy between FiO₂ 0.4 and 0.6 was 11.9 to -14.1%, and between FiO₂ 0.4 and 0.8 was 43.9 to -39.7%.

CONCLUSIONS

The E-COVX monitor evaluates V˙O₂ and V˙CO₂ in critical patients with mechanical ventilation with a clinically acceptable accuracy until FiO₂ 0.6.

Cardiac safety of lacosamide: the non-clinical perspective

OBJECTIVES

Lacosamide is indicated for the adjunctive treatment of partial-onset seizures in adult patients. Unlike other sodium channel-blocking antiepileptic drugs, lacosamide selectively enhances sodium channel slow inactivation. Potential effects of lacosamide on cardiac sodium channels and their cardiovascular consequences were comprehensively assessed. This manuscript presents the non-clinical cardiac safety profile of lacosamide.

METHODS

Lacosamide was tested in vitro on sodium and L-type calcium currents from isolated human atrial myocytes and on hERG-mediated potassium currents from stably transfected HEK293 cells. Cardiac action potentials were recorded in guinea pig ventricular myocytes. In vivo, hemodynamic and ECG parameters were evaluated in anesthetized dogs and monkeys receiving acute cumulative intravenous doses of lacosamide.

RESULTS

Following intravenous dosing with lacosamide, dose-dependent PR and QRS prolongation and ECG abnormalities (loss of P waves, atrioventricular and intraventricular blocks, junctional premature contractions) were observed in anesthetized dogs and monkeys. In vitro, lacosamide reduced human cardiac sodium currents in a concentration-, voltage- and state-dependent manner. Lacosamide reductions in Vmax in guinea pig myocytes were similar to lamotrigine and carbamazepine. Lacosamide showed no relevant inhibitory effects on hERG and L-type calcium channels and did not prolong QTc in vivo.

CONCLUSIONS

ECG findings in anesthetized animals correlate well with in vitro sodium channel-related effects and are also consistent with those (PR prolongation, first-degree atrioventricular block) reported in healthy volunteers and patients with epilepsy. Both in vivo and in vitro effects were detected from exposure levels 1.5- to 2-fold above those achieved with the maximum-recommended human lacosamide dose (400 mg/day).

Long-Term Mortality After Pneumonia in Cardiac Surgery Patients

Background:

The role that intensive care unit (ICU)-acquired pneumonia plays in the long-term outcomes of cardiac surgery patients is not well known. This study examined the association of pneumonia with in-hospital mortality and long-term mortality after adult cardiac surgery.

Methods:

A total of 2750 patients admitted to our ICU after cardiac surgery from January 2003 to December 2009 are the basis for this observational study. Patients who developed ICU-acquired pneumonia were matched with patients without it in a 1:2 ratio. The matching criteria were age, urgent or scheduled surgery, surgical procedure, and the propensity score for pneumonia. Multiple regression analysis was used to find predictors of hospital mortality. The relationship between pneumonia and long-term survival was analyzed with Kaplan-Meier survival estimates and a risk-adjusted Cox proportional regression model for patients discharged alive from hospital.

Results:

Pneumonia was diagnosed in 32 (1.2%) patients and there were 19 cases per 1000 days of mechanical ventilation. Patients with pneumonia had a significantly higher hospital mortality rate (28% vs 6.2%, P = .003) and a higher mortality at the end of follow-up (53% vs 19%, P < .0001) than those without it. Regression analysis showed that pneumonia was a strong predictor of hospital mortality. Five-year survival was as follows: pneumonia, 62%; control, 81%; and cohort patients, 91%. The Cox model showed that, after adjusting for confounding factors, patients with pneumonia (hazard ratio = 3.96, 95% confidence interval [CI]: 1.41-11.14) had poorer long-term survival.

Conclusion:

Pneumonia remains a serious complication in patients operated for cardiac surgery and is associated with increased hospital mortality and reduced long-term survival.

Glial modulation of synaptic transmission at the neuromuscular junction

The neuromuscular junction (NMJ) is a cholinergic synapse that controls muscle contraction. Glial cells, called perisynaptic Schwann cells, surround nerve terminals at the NMJ. Transmitter release induced by repetitive nerve stimulation, elicit a frequency-dependent activation of G-protein-coupled receptors on perisynaptic Schwann cells and the release of calcium from internal stores. In return, perisynaptic Schwann cells modulate synaptic activity during and following high-frequency stimulation through short-term plasticity. In the present review, we discuss evidence of glial involvement in the short-term plasticity at the NMJ and the potential impact of such modulation on synaptic efficacy.

[The immune status of Schwann cells: what is the role of the P2X7 receptor?]

The peripheral nervous system (PNS) displays structural barriers and a lack of lymphatic drainage which strongly limit the access of molecules and cells from the immune system. In addition, the PNS has the ability to set up some specific mechanisms of immune protection to limit the pathogenicity of inflammation processes following insults by pathogens or inflammatory autoimmune diseases like the Guillain-Barré syndrome. Schwann cells are among the most prominent cells which can display immune capabilities in the PNS. Numerous in vitro studies have shown that Schwann cells were indeed able to display a large repertoire of properties, ranging from the participation to antigen presentation, to secretion of pro- and anti-inflammatory cytokines, chemokines and neurotrophic factors. In vivo studies have confirmed the immune capabilities of Schwann cells. The aim of this review is to present how Schwann cells can participate to the initiation, the regulation and the termination of the immune response in the light of the recent discovery of the Schwann cell expression of purinergic P2X7 receptors.

Maturation and release of interleukin-1beta by lipopolysaccharide-primed mouse Schwann cells require the stimulation of P2X7 receptors

The P2X7 receptor, mainly expressed by immune cells, is a ionotropic receptor activated by high concentration of extracellular ATP. It is involved in several processes relevant to immunomodulation and inflammation. Among these processes, the production of extracellular interleukin-1beta (IL-1beta), a pro-inflammatory cytokine, plays a major role in the activation of the cytokine network. We have investigated the role of P2X7 receptor and of an associated calcium-activated potassium conductance (BK channels) in IL-1beta maturation and releasing processes by Schwann cells. Lipopolysaccharide-primed Schwann cells synthesized large amounts of pro-IL-1beta but did not release detectable amounts of pro or mature IL-1beta. ATP on its own had no effect on the synthesis of pro-IL-1beta, but a co-treatment with lipopolysaccharide and ATP led to the maturation and the release of IL-1beta by Schwann cells. Both mechanisms were blocked by oxidized ATP. IL-1beta-converting enzyme (ICE), the caspase responsible for the maturation of pro-IL-1beta in IL-1beta, was activated by P2X7 receptor stimulation. The specific inhibition of ICE by the caspase inhibitor Ac-Tyr-Val-Ala-Asp-aldehyde blocked the maturation of IL-1beta. In searching for a link between the P2X7 receptor and the activation of ICE, we found that enhancing potassium efflux from Schwann cells upregulated the production of IL-1beta, while strongly reducing potassium efflux led to opposite effects. Blocking BK channels actually modulated IL-1beta release. Taken together, these results show that P2X7 receptor stimulation and associated BK channels, through the activation of ICE, leads to the maturation and the release of IL-1beta by immune-challenged Schwann cells.

Modulation of neurotransmission by reciprocal synapse-glial interactions at the neuromuscular junction

Perisynaptic Schwann cells are glial cells that are closely associated with pre- and postsynaptic elements of the neuromuscular junction. Recent evidence shows that these cells detect and modulate neurotransmission in an activity-dependent fashion. Through G-protein signalling and Ca(2+) released from internal stores they can decrease or increase neurotransmitter release, respectively. Thus, they help to establish the level of neurotransmission associated with activity dependent short-term synaptic plasticity. We discuss evidence implicating perisynaptic Schwann cells as being active partners in neurotransmission at the neuromuscular junction, with emphasis on the modulation of short-term plasticity and potential implications for long-term changes.

ATP stimulation of P2X(7) receptors activates three different ionic conductances on cultured mouse Schwann cells

Extracellular ATP, by acting on P2 purinergic receptors, is a potent mediator of cell-to-cell communication both within and between the nervous and the immune systems. We show here by patch-clamp recording, fluorescent dye uptake and immunocytochemistry that, in cultured mouse Schwann cells, ATP activates a P2X(7) receptor associated with three different ionic conductances. In control conditions, ATP activated an inward current (I(ATP)) with a low potency (EC(50), 7.2 mM). Replacing ATP either by the ATP analogue 2',3'-O-(4-benzoyl-4-benzoyl)-ATP (BzATP) or by the tetraacidic form ATP(4-) potentiated the inward current (ATP(4-) EC(50), 375 microM). ATP and BzATP currents were strongly reduced by periodate oxidized ATP (oATP), an antagonist of P2X(7) receptors. IATP was a mixed current composed of a nonselective cationic conductance, a cationic conductance selective for K(+) and an anionic conductance selective for Cl(-). The activation of the K(+) conductance was dependent on an influx of Ca(2+), and was blocked by charybdotoxin (ChTX) and tetraethylammonium (TEA), two potent antagonists of large conductance Ca(2+)-activated K(+) channels (BK channels). The activation of the Cl(-) conductance was insensitive to Ca(2+) but required the presence of K(+). Total removal of K(+) blocked both the Ca(2+)-activated K(+) conductance and the Cl(-) conductance, unveiling the P2X(7) nonselective cationic conductance. The P2X(7) receptor was localized by immunocytochemistry using a polyclonal antibody, anti-P2X(7), whilst its expression and functionality were both detected by the uptake of Lucifer Yellow. This receptor could regulate the synthesis and the release of cytokines by Schwann cells during pathophysiological events.

Spontaneous neuronal activity in organotypic cultures of mouse dorsal root ganglion leads to upregulation of calcium channel expression on remote Schwann cells

It is well established that neurons regulate the properties of both central and peripheral glial cells. Some of these neuro-glial interactions are modulated by the pattern of neuronal electrical activity. In the present work, we asked whether blocking the electrical activity of dorsal root ganglion (DRG) neurons in vitro by a chronic treatment with tetrodotoxin (TTX) would modulate the expression of the T-type Ca(2+) channel by mouse Schwann cells. When recorded in their culture medium, about one-half of the DRG neurons spontaneously fired action potentials (APs). Treatment for 4 days with 1 microM TTX abolished both spontaneous and evoked APs in DRG neurons and in parallel significantly reduced the percentage of Schwann cells expressing Ca(2+) channel currents. On the fraction of Schwann cells still expressing Ca(2+) channel currents, these currents had electrophysiological parameters (mean amplitude, mean inactivation time constant, steady-state inactivation curve) similar to those of control cultures. Co-treatment for 4 days with 1 microM TTX and 2 mM CPT-cAMP, a cAMP analogue that induces the expression de novo of Ca(2+) channel currents in Schwann cells deprived of neurons, maintained the percentage of Schwann cells expressing Ca(2+) channel currents, showing that TTX does not directly affect the expression of Ca(2+) channel currents by Schwann cell. We conclude that blocking spontaneous activity of DRG neurons in vitro downregulates Ca(2+) channel expression by Schwann cells. These results strongly suggest that DRG neurons upregulate Ca(2+) channel expression by Schwann cells via the release of a diffusible factor whose secretion is dependent on electrical activity.