Drug induced QT prolongation: the measurement and assessment of the QT interval in clinical practice

KH176 under development for rare mitochondrial disease: a first in man randomized controlled clinical trial in healthy male volunteers

Background

Mitochondrial disorders are a clinically, biochemically and genetically heterogeneous group of multi-system diseases, with an unmet medical need for treatment. KH176 is an orally bio-available small molecule under development for the treatment of mitochondrial(−related) diseases. The compound is a member of a new class of drugs, acting as a potent intracellular redox-modulating agent essential for the control of oxidative and redox pathologies. The aim of this randomized, placebo controlled, double-blinded phase 1 study was to test safety, tolerability and pharmacokinetics of single and multiple doses of KH176 in healthy male volunteers. Putative effects on redox related biomarkers were explored.

Results

KH176 was well tolerated up to and including a single dose of 800 mg and multiple doses of 400 mg b.i.d. for 7 Days. However, when the QT interval was corrected for heart rate, administration of single doses of 800 and 2000 mg and at a multiple dose of 400 mg KH176 had marked effects. Post-hoc analysis of the ECGs showed clear changes in cardiac electrophysiology at single doses of 800 and 2000 mg and multiple doses of 400 mg b.i.d.. At lower doses, detailed ECG analysis showed no changes in electrophysiology compared to placebo. Exposure-response modelling of the cardiac intervals revealed an exposure range of KH176 without effects on cardiac conduction and provided a threshold of 1000 ng/mL above which changes in intervals could occur. After single- and multiple-dose administration, the pharmacokinetics of KH176 was more than dose proportional. KH176 accumulated to a small extent and food only slightly affected the pharmacokinetics of KH176, which was considered clinically irrelevant. Renal excretion of unchanged KH176 and its metabolite represents a minor pathway in the elimination of KH176. As expected in healthy volunteers no effects on redox biomarkers were observed.

Conclusion

The study deemed that KH176 is well tolerated up to single doses of 800 mg and multiple doses of 400 mg b.i.d. and has a pharmacokinetic profile supportive for a twice daily dosing. Only at high doses, KH176 causes clinically relevant changes in cardiac electrophysiology, including prolonged QTc interval and changes in T wave morphology. A Phase 2 clinical trial (100 mg b.i.d., orally) has been conducted recently of which the final results are expected Q1 2018.

Trial registration

NCT02544217. Registered. ISRCTN43372293. Retrospectively registered.

Electronic supplementary material

The online version of this article (10.1186/s13023-017-0715-0) contains supplementary material, which is available to authorized users.

QT interval prolongation in opioid agonist treatment: analysis of continuous 12-lead electrocardiogram recordings

AIMS

Methadone is a widely used opioid agonist treatment associated with QT prolongation and torsades de pointes. We investigated the QT interval in patients treated with methadone or buprenorphine using continuous 12-lead Holter recordings.

METHODS

We prospectively made 24-h Holter recordings in patients prescribed methadone or buprenorphine, compared to controls. After their normal dose a continuous 12-lead Holter recorder was attached for 24 h. Digital electrocardiograms were extracted hourly from the Holter recordings. The QT interval was measured automatically (H-scribe software, Mortara Pty Ltd) and checked manually. The QT interval was plotted against heart rate (HR) on the QT nomogram to determine abnormality. Demographics, dosing, medical history and laboratory investigations were recorded.

RESULTS

There were 58 patients (19 methadone, 20 buprenorphine and 19 control); median age 35 years (20-56 years); 33 males. Baseline characteristics were similar. Median dose of methadone was 110 mg day-1 (70-170 mg day-1 ) and buprenorphine was 16 mg day-1 (12-32 mg day-1 ). Seven participants had abnormal QT intervals. There was a significant difference in the proportion of prescribed methadone with abnormal QT intervals, 7/19 (37%; 95% confidence interval: 17-61%), compared to controls 0/19 (0%; 95% confidence interval: 0-21%; P = 0.008), but no difference between buprenorphine and controls (0/20). QT vs. HR plots showed patients prescribed methadone had higher QT-HR pairs over 24 h compared to controls. There was no difference in dose for patients prescribed methadone with abnormal QT intervals and those without.

CONCLUSIONS

Methadone is associated with prolonged QT intervals, but there was no association with dose. Buprenorphine did not prolong the QT interval. Twenty four-hour Holter recordings using the QT nomogram is a feasible method to assess the QT interval in patients prescribed methadone.

Optimizing QT Interval Measurement for the Preparticipation Screening of Young Athletes

PURPOSE

Sudden cardiac death is the leading cause of death in athletes. Long QT syndrome (LQTS) is one of the most common cardiogenetic diseases that can lead to sudden cardiac death and is identified by QT interval prolongation on an ECG. Recommendations for QT monitoring in athletes are adopted from nonathlete populations. To improve screening, ECG data of athletes are assessed to determine a more appropriate method for QT interval estimation.

METHODS

ECG (CardeaScreen) data were collected from June 2010 to March 2015. ECG data with HR greater than 100 bpm were excluded. Fiducial points of outliers were manually corrected if the QRS onset or the T wave offset was misidentified. A model of best fit was determined and compared across four QT correction factors. Classification analysis was used to compare the Bazett's corrected QT interval to the 99th percentile of uncorrected QT interval.

RESULTS

High school (n = 597), college (n = 1207), and professional athletes (n = 273) (N = 2077) were analyzed. Mean age was 19 ± 3.5 yr. QT interval varied by cohort (HS = 388 ± 30, Col = 410 ± 33, Pro = 407 ± 27, p < 0.0001). A nonlinear power function with a cubic exponent of -0.349 fit the data the best (R = 0.64). Of the four common correction factors, Fridericia had the lowest residual dependence to HR (m = -0.10). With standard screening, 75% of athletes within the top 1% for QT interval were not identified for further investigation for LQTS.

CONCLUSION

Up to 75% of athletes possessing an uncorrected QT interval greater than 99% of the population are not identified for investigation for LQTS using the recommended criteria. We propose a new method of risk stratification that replaces QT interval correction. Further study is needed to establish QT interval distributions and risk thresholds in athletes.

GENomE wide analysis of sotalol-induced IKr inhibition during ventricular REPOLarization, "GENEREPOL study": Lack of common variants with large effect sizes

Many drugs used for non-cardiovascular and cardiovascular purposes, such as sotalol, have the side effect of prolonging cardiac repolarization, which can trigger life-threatening cardiac arrhythmias by inhibiting the potassium-channel IKr (KCNH2). On the electrocardiogram (ECG), IKr inhibition induces an increase in QTc and Tpeak-Tend (TpTe) interval and a decrease of T wave maximal amplitude (TAmp). These changes vary markedly between subjects, suggesting the existence of predisposing genetic factors. 990 healthy individuals, prospectively challenged with an oral 80mg sotalol dose, were monitored for changes in ventricular repolarization on ECG between baseline and 3 hours post dosing. QTc and TpTe increased by 5.5±3.5% and 15±19.6%, respectively, and TAmp decreased by 13.2±15.5%. A principal-component analysis derived from the latter ECG changes was performed. A random subsample of 489 individuals were subjected to a genome-wide-association analysis where 8,306,856 imputed single nucleotide polymorphisms (SNPs) were tested for association with QTc, TpTe and TAmp modulations, as well their derived principal-components, to search for common genetic variants associated with sotalol-induced IKr inhibition. None of the studied SNPs reached the statistical threshold for genome-wide significance. This study supports the lack of common variants with larger effect sizes than one would expect based on previous ECG genome-wide-association studies.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov NCT00773201.

Prolongation of the QTc interval in HIV-infected individuals compared to the general population

OBJECTIVES

Prolonged QT interval is associated with arrhythmias and sudden death. An increased prevalence of QT interval prolongation in human immunodeficiency virus-infected (HIV) subjects was previously described. The impact of different medications and HIV infection itself on the QT interval is rarely investigated in large HIV+ cohorts.

METHODS

We compared QT interval measurement in 496 HIV(+) patients of the HIV-HEART study (HIVH) and 992 sex- and age-matched controls of the population-based German Heinz Nixdorf Recall study (HNR). QT corrected for heart rate (QTc) >440 ms in male and >460 ms in female was considered pathological. We analysed the impact of HIV status and HIV medication on QTc prolongation in the HIVH subjects.

RESULTS

We observed longer QTc in HIVH subjects compared with HNR controls: 424.1 ms ± 23.3 vs. 411.3 ± 15.3 ms for male and 435.5 ms ± 19.6 vs. 416.4 ms ± 17.3 for female subjects (p < 0.0001 for both sexes). Adjusting for QT prolonging medication the mean differences in QTc between the two studies remained significant with 12.6 ms (95% CI 10.5-14.8; p value <0.0001) for male and 19.3 ms (95% CI 14.5-24.2; p value <0.0001) for female subjects. Prolongation of QTc was pathologic in 22.8 vs. 3.9% of HIV(+) and non-infected males and in 12.1 vs. 1.8% of the females [OR of 7.9 (5.0-12.6) and OR of 6.7 (1.8-24.2), respectively]. Smoking behaviour was an independent factor to lengthen QTc in HIV(+) patients. Diabetes mellitus was not a risk factor itself, but might be associated with medication which was associated with LQT. We could not observe any influence of the HIV status, ART, or any co-medication on the QTc.

CONCLUSIONS

Our study showed that HIV(+) patients had significantly longer QTc intervals compared to the general population. The number of patients with pathologic QTc prolongation was significantly increased in HIV(+) population.

Unintended Consequences of Adjusting Citalopram Prescriptions Following the 2011 FDA Warning

OBJECTIVES

In 2011, the U.S. Food and Drug Administration (FDA) issued a safety announcement cautioning providers against prescribing citalopram above 40 mg per day given concerns for QT prolongation. We assessed the impact of a health system quality improvement initiative to identify patients taking higher than the recommended dose of citalopram.

DESIGN

Retrospective cohort study.

SETTING

Nine primary care clinics within the University of Michigan from March 2012 to February 2013.

PARTICIPANTS

Adult patients taking a higher-than-recommended dose of citalopram following the FDA warning in 2011 (N = 199).

MEASUREMENTS

Frequency of EKG monitoring, clinical factors associated with patients whose citalopram dose or use was adjusted, and potential impact of these changes on overall health care utilization was assessed.

RESULTS

In patients prescribed higher-than-recommended doses of citalopram and who received a note from a pharmacist regarding the FDA warnings, only 8.5% received electrocardiogram (EKG) monitoring. Patients who were converted to an alternative antidepressant from citalopram were more likely to receive subsequent new prescriptions for benzodiazepines and sedative hypnotics (χ² = 7.9, p = 0.048). Patients who had any adjustments to their antidepressant medication had greater overall health care utilization (OR: 25.0; 95% CI: 5.7-109.6; p < 0.001) than patients remaining on the same dose of citalopram.

CONCLUSIONS

Despite a targeted quality intervention to address the FDA warning regarding citalopram, the warning was associated with low levels of EKG monitoring, increased anxiolytic and sedative medication use, and higher healthcare utilization. This finding may represent destabilization of patients on previously therapeutic doses of their antidepressant and an unintended consequence of the FDA warning.

QTc prolongation during erythromycin used as prokinetic agent in ICU patients

Background

High-dose erythromycin used as antibiotic prolongs QTc interval. Low-dose erythromycin is frequently used as a prokinetic agent, especially in patients in the intensive care unit (ICU). It is unknown whether low-dose erythromycin affects cardiac repolarisation and puts patients at risk for torsades de pointes.

Methods

In this prospective study, we included ICU patients treated with erythromycin as prokinetic in a dose of 200 mg twice a day. An ECG was performed before, 15 min and 24 hours after the start of erythromycin. Cardiac repolarisation was assessed by rate-corrected analysis of the QT interval (QTc) on the ECG by two independent investigators. Starting or stopping other possibly QTc prolonging drugs during the study period was an exclusion criterion. Wilcoxon signed-rank test and Friedman's test were used for statistical analysis to assess prolongation of QTc. Primary outcome was defined by the prolongation of QTc after 15 min and 24 hours.

Results

51 patients were eligible for this study. In these patients, QTc increased significantly from 430 ms at baseline to 439 ms (p=0.03) after 15 min and 444 ms (p=0.01) after 24 hours. After 15 min and 24 hours, the upper limit of 95% CI for prolongation of QTc was well above 10 ms. No QTc-related arrhythmias were seen.

Conclusions

During treatment with erythromycin in a dose of 200 mg twice a day. QTc prolonged mildly but significantly. Sequential ECG registration should be performed when low-dose erythromycin is prescribed, especially in the presence of other risk factor for QTc prolongation.

Clemizole hydrochloride blocks cardiac potassium currents stably expressed in HEK 293 cells

BACKGROUND AND PURPOSE

Clemizole, a histamine H₁ receptor antagonist has a potential therapeutic effect on hepatitis C infection and also potently inhibits TRPC5 ion channels. The aim of the present study was to investigate whether clemizole blocks cardiac K⁺ currents and thus affects cardiac repolarization.

EXPERIMENTAL APPROACH

Whole-cell patch techniques was used to examine the effects of clemizole on hERG channel current, I_Ks and K_v 1.5 channel current in HEK 293 cell expression systems as well as on ventricular action potentials of guinea pig hearts. Isolated hearts from guinea pigs were used to determine the effect on the ECG.

KEY RESULTS

Clemizole decreased hERG current by blocking both open and closed states of the channel in a concentration-dependent manner (IC₅₀ : 0.07 μM). The S631A, S636A, Y652A and F656V hERG mutant channels reduced the inhibitory effect of clemizole (IC₅₀ : 0.82, 0.89, 1.49 and 2.98 μM, respectively), suggesting that clemizole is a pore blocker of hERG channels. Clemizole also moderately decreased I_Ks and human K_v 1.5 channel current. Moreover, clemizole increased the duration of the ventricular action potential in guinea pig hearts and the QTc interval in isolated perfused hearts from guinea pigs, in a concentration-dependent manner (0.1-1.0 μM).

CONCLUSION AND IMPLICATIONS

Our results provide the first evidence that clemizole potently blocks hERG channels, moderately inhibits cardiac I_Ks , delays cardiac repolarization and thereby prolongs QT interval. Thus, caution should be taken when clemizole is used as a TRPC5 channel blocker or for treating hepatitis C infection.

Estimation of the QT-RR relation: trade-off between goodness-of-fit and extrapolation accuracy

Correction of the QT interval in the ECG for changes in heart rate (RR interval) is needed to compare groups of patients and assess the risk of sudden cardiac death. The QTc represents the QT interval at 60 bpm, although most patients typically have a faster heart rate, thus requiring extrapolation of the QT-RR relationship.

OBJECTIVE

This paper investigates the ability of QT-RR models with increasing number of parameters to fit beat-to-beat variations in the QT interval and provide a reliable estimate of the QTc.

APPROACH

One-, two- and three-parameter functions generalising the Bazett and Fridericia formulas were used in combination with hysteresis reduction (memory) obtained by time-averaging the history of RR intervals with exponentially-decaying weights. In normal men and women datasets of Holter recordings in normal subjects (24 h monitoring), two measures were computed for each model: the root mean square error (RMSE) of fitting and the difference between the estimated QTc and a reference QTc obtained by collecting data points around RR  =  1000 ms.

MAIN RESULTS

The two- and three-parameter functions all gave similar low RMSE with uncorrelated residues. An optimal memory parameter was found that still minimized the RMSE and could be used for all functions and subjects. This reduction in RMSE resulted from changes in the parameters linked to the increased steepness of the QT-RR relation after hysteresis reduction. At optimal memory, the two and three-parameter models provided poorer prediction of the QTc as compared to the Fridericia's model in subjects with fast heart rates, since accurate representation of the steeper QT-RR relation worsened the extrapolation that was then needed to determine the QTc.

SIGNIFICANCE

As a result, among all models investigated, the Fridericia formulation offered the best trade-off for QTc prediction robust to memory and fast heart rates.

QT prolongation caused by insulin-induced hypoglycaemia - An interventional study in 119 individuals

AIMS

Hypoglycaemia is associated with increased risk of cardiovascular events and mortality in patients with diabetes, but the extent and mechanisms of this link are ill defined. We here prospectively studied cardiac repolarization abnormalities during insulin-induced hypoglycaemia in humans.

METHODS

119 individuals (69 males, age 47.5±13.4years, range 18-82years) were assessed during hypoglycaemia after the injection of 0.1-0.25units/kg human insulin. Corrected QT intervals (QTc) and QT dispersion (QTd) were calculated from serially recorded twelve lead electrocardiograms, and plasma glucose and other endocrine markers were studied.

RESULTS

QTc increased from 415.1±21.9ms (mean±standard deviation) at baseline to 444.9±26.5ms during hypoglycaemia (plasma glucose nadir, 1.6±0.5mmol/L, p=0.001), accompanied by an increase of QTd from 45.0±22.7ms to 64.1±40.0ms (p<0.001). Hypoglycaemia-induced abnormal QTc prolongation (defined as ⩾460ms in females and ⩾450ms in males) occurred in 17% (9/54) of females and 26% (17/65) of males. 97 of 119 of individuals (82%) developed transient hypokalaemia (K⁺ ⩽3.6mmol/L), and plasma epinephrine increased from 220.4±169.5pmol/L at baseline to 2945.6±2421.4pmol/L during hypoglycaemia. Baseline QTc, but not age or gender, was a significant predictor of hypoglycaemia-induced QTc prolongation (p=0.001).

CONCLUSIONS

Insulin-induced hypoglycaemia frequently causes abnormal QT prolongation and is associated with hypokalaemia and sympathoadrenal activation, thereby increasing the potential risk for ventricular arrhythmias, particularly in individuals with pre-existing high normal QTc.

A case report of QT prolongation with glycopyrronium bromide in a patient with chronic tamoxifen use

Background

Glycopyrronium bromide has recently been approved as a once daily maintenance inhalation therapy for moderate to severe chronic obstructive pulmonary disease (COPD). Efficacy and safety trial data have found rare cases of significant QT prolongation. To our knowledge, we describe the first case report of QT prolongation >600 ms with initiation of glycopyrronium bromide in a real world setting.

Case presentation

A 78-year-old female with moderate COPD recently started on glycopyrronium bromide, presented to Emergency Department (ED) with syncope. Her past medical history was significant for a left total mastectomy and she had been on Tamoxifen for 9 months. One day prior to her presentation, she had visited a naturopathic clinic for a vitamin infusion resulting in emesis. The following day she continued to feel dizzy and had a witnessed syncopal episode without any reported cardiac or neurological symptoms preceding the event or after regaining consciousness. In the emergency department, she reported dizziness and was found to be hypotensive. Her symptoms completely resolved with intravenous fluids. Lab work was normal however her electrocardiogram (ECG) demonstrated a QTc interval of 603 and 631 ms (Friderica and Bazett’s respectively) with a normal QT interval on her baseline ECG prior to initiating Tamoxifen. She was admitted to the Cardiology service for further work-up of QT prolongation. Her syncope was felt to be due to orthostatic hypotension and the QT prolongation secondary to medications, which were both discontinued during her admission. After 2 days, her QT interval normalized consistent with the half-life of Glycopyrronium bromide (13–57 h) compared to Tamoxifen (8–14 days).

Conclusion

Glycopyrronium bromide is guideline recommended as first line therapy for prevention of exacerbation in moderate to severe COPD however safety data had been limited to select populations. This case report highlights the need for future studies to identify high-risk populations at potential risk of life-threatening arrhythmias who may benefit from periodic ECG surveillance.

Detecting and Managing Adverse Effects of Antipsychotic Medications: Current State of Play

Antipsychotics are some of the most frequently prescribed medications not only for psychotic disorders and symptoms but also for a wide range of on-label and off-label indications. Because second-generation antipsychotics have largely replaced first-generation antipsychotics as first-line options due to their substantially decreased risk of extrapyramidal side effects, attention has shifted to other clinically concerning adverse events associated with antipsychotic therapy. The focus of this article is to update the nonextrapyramidal side effects associated with second-generation antipsychotics. Issues surrounding diagnosis and monitoring as well as clinical management are addressed.

Metabolomic patterns associated to QTc interval in shiftworkers: an explorative analysis

OBJECTIVES

(1)H NMR-metabolomic approach was used to investigate QTc interval correlation with plasma metabolic profiles in shiftworkers.

METHODS

Socio-demographic data, electrocardiographic QTc interval and plasma metabolic profiles from 32 male shiftworkers, were correlated by multivariate regression analysis.

RESULTS

We found a positive correlation between QTc interval values, body mass index, glycemia and lactate level and a negative correlation between QTc interval and both pyroglutamate and 3-hydroxybutyrate plasma level.

CONCLUSIONS

Our analysis provides evidence of the association between clinical, metabolic profiles and QTc interval values. This could be used to identify markers of early effects and/or susceptibility in shiftworkers.

Single therapeutic and supratherapeutic doses of sacubitril/valsartan (LCZ696) do not affect cardiac repolarization

Purpose

Sacubitril/valsartan (LCZ696) is a first-in-class angiotensin receptor neprilysin inhibitor (ARNI) indicated to reduce the risk of cardiovascular death and hospitalization for heart failure in patients with chronic heart failure (NYHA class II–IV) and reduced ejection fraction. This study was aimed to evaluate the effect of single oral therapeutic (400 mg) and supratherapeutic (1200 mg) doses of LCZ696 on cardiac repolarization.

Method

This randomized double-blind crossover study in healthy male subjects compared the effect of therapeutic and supratherapeutic doses of LCZ696 with placebo and moxifloxacin 400 mg (open-label treatment) as positive control. The primary assessment was mean baseline- and placebo-corrected QTcF (∆∆QTcF; Fridericia correction). Additional assessments included the ∆∆QTcB (Bazett’s correction), PR interval, QRS duration, heart rate (HR), LCZ696 pharmacokinetics, pharmacokinetic/pharmacodynamic relationships, and safety.

Results

Of the 84 subjects enrolled, 81 completed the study. The maximum upper bound of the two-sided 90 % confidence interval for ∆∆QTcF for LCZ696 400 mg and 1200 mg were <10 ms, and assay sensitivity was confirmed with moxifloxacin. No relevant treatment-emergent changes were observed in any of the ECG-derived parameters with LCZ696 or placebo, and the incidence of adverse events was comparable among the treatment groups.

Conclusion

Single therapeutic and supratherapeutic doses of LCZ696 did not affect cardiac repolarization as defined by the E14 ICH guidelines.

Electronic supplementary material

The online version of this article (doi:10.1007/s00228-016-2062-9) contains supplementary material, which is available to authorized users.

Propofol-associated QTc prolongation

OBJECTIVES

Propofol is a preferred agent for sedation in patients in the intensive care unit (ICU) due, in part, to its established safety profile. Despite this, recent case reports have suggested a potential for prolongation of the corrected QT interval (QTc) in ICU patients receiving propofol, though limited empirical work has been conducted to evaluate this association. As such, the purpose of this study was to assess the relationship between propofol infusion and QTc prolongation in a historical cohort of ICU patients.

METHODS

A single-center, historical, observational, pre-post cohort analysis of medical records from admitted patients ⩾18 years old with cardiovascular disease was conducted, involving cases who received propofol infusion for ⩾3 hours with sequential electrocardiogram monitoring from 2006 to 2012. A multivariable, generalized linear model regression was employed to assess the primary outcome of on-propofol QTc interval (QTc2), controlling for various demographic and clinical factors.

RESULTS

A total of 96 patients met inclusion criteria, averaging 56.1 ± 14.1 years of age and 86.1 ± 25.0 kg, with 37.5% being female. A mean prolongation in QTc interval of 30.4 ± 55.5 ms (p < 0.001) was observed during the propofol infusion, with 43.8% of cases exhibiting an on-infusion QTc2 of ⩾ 500 ms. Regression analyses suggested that prolongation in on-propofol QTc was independently associated with baseline QTc interval and amiodarone use, while weight as inversely associated with QTc2 (p < 0.05).

CONCLUSION

This historical cohort analysis of adult ICU patients receiving propofol suggests that on-infusion QTc prolongation was associated with increasing baseline QTc interval and with amiodarone use. Further research is needed to evaluate the clinical significance and cause-and-effect relationship between potential QTc changes and propofol use in the ICU.

Citalopram Overdose: a Fatal Case

BACKGROUND

Citalopram is a selective serotonin reuptake inhibitor (SSRI) with cardiac and neurologic toxicities as well as the potential for serotonin syndrome. In most instances, patients recover fully from toxic ingestions of SSRIs. We describe a fatal case of a citalopram overdose.

CASE REPORT

A 35-year-old woman presented to the emergency department after having witnessed seizures at home. An empty citalopram prescription bottle was located, and an intentional overdose was suspected. At the scene, she was found to be in cardiac arrest with pulseless electrical activity and underwent cardiopulmonary resuscitation, including intravenous epinephrine and bicarbonate. In the emergency department, her physical exam was notable for cough and gag reflexes and movement in all extremities with increased muscle tone and tachycardia. Her initial postresuscitation ECG showed sinus rhythm with QRS 92 ms and QTc 502 ms. Her temperature was initially normal, but she rapidly became febrile to 41.8 °C shortly after admission. She was treated symptomatically and with cyproheptadine for suspected serotonin syndrome (SS) but became increasingly hemodynamically unstable over the next 6 h and then developed torsades des pointes (TdP) progressing to pulseless, wide complex tachycardia. She underwent cardiopulmonary resuscitation (CPR) for approximately 50 min but ultimately expired. Postmortem serum analysis revealed a citalopram concentration of 7300 ng/mL (therapeutic range 9-200 ng/mL) and THC, but no other non-resuscitation drugs or substances.

CASE DISCUSSION

Citalopram overdoses often have only mild to moderate symptoms, particularly with ingestions under 600 mg in adults. However, with higher doses, severe manifestations have been described, including QTc prolongation, TdP, and seizures. Serotonin syndrome has also been described in SSRI overdose, and our patient exhibited signs consistent with SS, including increased muscle tone and autonomic dysregulation. Our patient's serum concentration suggests a massive overdose, with major clinical effects, possible SS, and death.

CONCLUSIONS

Although most patients recover from citalopram overdose, high-dose ingestions can produce severe effects and fatalities may occur. In this case, it is likely that the patient's delayed presentation also contributed significantly to her death. The clinician must be aware of the potential for large ingestions of citalopram to produce life-threatening effects and monitor closely for the neurologic, cardiovascular, and other manifestations that, in rare cases, can be fatal.

QT interval and drug therapy

The QT interval is an important component of the electrocardiogram, which when prolonged can predict the risk of developing the potentially fatal cardiac arrhythmia, torsades de pointes. There is growing understanding of the genetics associated with cardiac arrhythmias and an increasing number of drugs that can prolong the QT interval. Consequently, assessment of the effect of drugs on the QT interval has become a significant aspect of drug development, regulatory assessment and clinical care. Here, we review the QT interval and the risks associated with drug-induced prolongation of the QT interval.

The Effect of a Combination Treatment Using Palonosetron, Promethazine, and Dexamethasone on the Prophylaxis of Postoperative Nausea and Vomiting and QTc Interval Duration in Patients Undergoing Craniotomy under General Anesthesia: A Pilot Study

Introduction

Postoperative nausea and vomiting (PONV) is a displeasing experience that distresses surgical patients during the first 24 h after a surgical procedure. The incidence of postoperative nausea occurs in about 50%, the incidence of postoperative vomiting is about 30%, and in high-risk patients, the PONV rate could be as high as 80%. Therefore, the study design of this single arm, non-randomized, pilot study assessed the efficacy and safety profile of a triple therapy combination with palonosetron, dexamethasone, and promethazine to prevent PONV in patients undergoing craniotomies under general anesthesia.

Methods

The research protocol was approved by the institutional review board and 40 subjects were provided written informed consent. At induction of anesthesia, a triple therapy of palonosetron 0.075 mg IV, dexamethasone 10 mg IV, and promethazine 25 mg IV was given as PONV prophylaxis. After surgery, subjects were transferred to the surgical intensive care unit or post anesthesia care unit as clinically indicated. Ondansetron 4 mg IV was administered as primary rescue medication to subjects with PONV symptoms. PONV was assessed and collected every 24 h for 5 days via direct interview and/or medical charts review.

Results

The overall incidence of PONV during the first 24 h after surgery was 30% (n = 12). The incidence of nausea and emesis 24 h after surgery was 30% (n = 12) and 7.5% (n = 3), respectively. The mean time to first emetic episode, first rescue, and first significant nausea was 31.3 (±33.6), 15.1 (±25.8), and 21.1 (±25.4) hours, respectively. The overall incidence of nausea and vomiting after 24–120 h period after surgery was 30% (n = 12). The percentage of subjects without emesis episodes over 24–120 h postoperatively was 70% (n = 28). No subjects presented a prolonged QTc interval ≥500 ms before and/or after surgery.

Conclusion

Our data demonstrated that this triple therapy regimen may be an adequate alternative regimen for the treatment of PONV in patients undergoing neurological surgery under general anesthesia. More studies with a control group should be performed to demonstrate the efficacy of this regimen and that palonosetron is a low risk for QTc prolongation.

ClinicalTrials.gov Identifier

NCT02635828 (https://clinicaltrials.gov/show/NCT02635828).

Tyrosine Kinase Inhibitors for the Treatment of Chronic-Phase Chronic Myeloid Leukemia: Long-Term Patient Care and Management

Several tyrosine kinase inhibitors (TKIs) are now approved for the treatment of chronic myeloid leukemia in chronic phase. The efficacy of these drugs has been repeatedly demonstrated, as has their tolerability in most patients. However, late and chronic toxicities become an important issue for many patients facing long-term TKI exposure. For patients on long-term imatinib, gastrointestinal events, fluid retention, muscle cramps, fatigue, and hepatotoxicity are among the most common and most clinically relevant adverse events (AEs). A few of these have also emerged as important AEs with some of the newer TKIs. Distinct long-term toxicity concerns have emerged for dasatinib (pleural effusion, pulmonary hypertension, headache, and dyspnea) and nilotinib (rash, headache, myalgia, alopecia, and hyperglycemia), whereas due to the recent approval of bosutinib and ponatinib, their long-term toxicity profiles have not been fully characterized. Clinical experience with each of these drugs is accumulating, and ensuring proper adherence and monitoring for potential AEs is essential for effective treatment.

SKF-96365 blocks human ether-à-go-go-related gene potassium channels stably expressed in HEK 293 cells

SKF-96365 is a TRPC channel antagonist commonly used to characterize the potential functions of TRPC channels in different systems, which was recently reported to induce QTc prolongation on ECG by inhibiting TRPC channels. The present study investigates whether the blockade of cardiac repolarization currents would be involved in the increase of QTc interval. Cardiac repolarization currents were recorded in HEK 293 cells stably expressing human ether-à-go-go-related gene potassium (hERG or hKv11.1) channels, hKCNQ1/hKCNE1 channels (IKs) or hKir2.1 channels and cardiac action potentials were recorded in guinea pig ventricular myocytes using a whole-cell patch technique. The potential effect of SKF-96365 on QT interval was evaluated in ex vivo guinea pig hearts. It was found that SKF-96365 inhibited hERG current in a concentration-dependent manner (IC50, 3.4μM). The hERG mutants S631A in the pore helix and F656V of the S6 region reduced the inhibitory sensitivity with IC50s of 27.4μM and 11.0μM, suggesting a channel pore blocker. In addition, this compound inhibited IKs and hKir2.1currents with IC50s of 10.8 and 8.7μM. SKF-96365 (10μM) significantly prolonged ventricular APD90 in guinea pig ventricular myocytes and QTc interval in ex vivo guinea pig hearts. These results indicate that the TRPC channel antagonist SKF-96365 exerts blocking effects on hERG, IKs, and hKir2.1 channels. Prolongation of ventricular APD and QT interval is related to the inhibition of multiple repolarization potassium currents, especially hERG channels.

Xenon does not increase heart rate-corrected cardiac QT interval in volunteers and in patients free of cardiovascular disease

BACKGROUND

Impaired cardiac repolarization, indicated by prolonged QT interval, may cause critical ventricular arrhythmias. Many anesthetics increase the QT interval by blockade of rapidly acting potassium rectifier channels. Although xenon does not affect these channels in isolated cardiomyocytes, the authors hypothesized that xenon increases the QT interval by direct and/or indirect sympathomimetic effects. Thus, the authors tested the hypothesis that xenon alters the heart rate-corrected cardiac QT (QTc) interval in anesthetic concentrations.

METHODS

The effect of xenon on the QTc interval was evaluated in eight healthy volunteers and in 35 patients undergoing abdominal or trauma surgery. The QTc interval was recorded on subjects in awake state, after their denitrogenation, and during xenon monoanesthesia (FetXe > 0.65). In patients, the QTc interval was recorded while awake, after anesthesia induction with propofol and remifentanil, and during steady state of xenon/remifentanil anesthesia (FetXe > 0.65). The QTc interval was determined from three consecutive cardiac intervals on electrocardiogram printouts in a blinded manner and corrected with Bazett formula.

RESULTS

In healthy volunteers, xenon did not alter the QTc interval (mean difference: +0.11 ms [95% CI, -22.4 to 22.7]). In patients, after anesthesia induction with propofol/remifentanil, no alteration of QTc interval was noted. After propofol was replaced with xenon, the QTc interval remained unaffected (417 ± 32 ms vs. awake: 414 ± 25 ms) with a mean difference of 4.4 ms (95% CI, -4.6 to 13.5).

CONCLUSION

Xenon monoanesthesia in healthy volunteers and xenon/remifentanil anesthesia in patients without clinically relevant cardiovascular disease do not increase QTc interval.

The Half RR Rule: A Poor Rule of Thumb and Not a Risk Assessment Tool for QT Interval Prolongation

OBJECTIVES

Measuring the QT interval on an electrocardiogram (ECG) is integral to risk assessment of Torsade de Pointes (TdP). This study aimed to investigate the accuracy of the 1/2 RR rule as a risk assessment tool for drug-induced TdP, comparing it to the QT nomogram, Bazett's corrected QT (QTcB), and Fridericia's corrected QT (QTcF).

METHODS

The authors calculated sensitivity and specificity of the 1/2 RR rule using a published data set of 129 cases of drug-induced TdP and 316 controls (noncardiotoxic overdoses), compared to the QT nomogram, QTcB > 500 msec and QTcF > 500 msec. To further determine the value of the 1/2 RR rule, its observed positive, and negative agreement were calculated when compared to the QT nomogram for determining an abnormal QT in eight samples of different drugs in overdose.

RESULTS

The sensitivity and specificity of the 1/2 RR rule were 88% (95% confidence interval [CI] = 80% to 93%) and 53% (95% CI = 47% to 58%), respectively, compared to the QT nomogram (sensitivity = 97%, 95% CI = 92% to 99%; specificity = 99%, 95% CI = 97% to 100%). It was also less sensitive than QTcB > 500 msec and had a lower specificity than QTcB > 500 msec and QTcF > 500 msec. In drug overdose patients, the 1/2 RR rule had poor observed agreement averaging 41%, which was mainly due to poor positive agreement, except for amisulpride where there was good agreement.

CONCLUSIONS

The 1/2 RR rule was not as sensitive as the QT nomogram or QTcB > 500 msec for drug-induced TdP. It had poor positive agreement in almost all overdose patients, resulting in over half of patients receiving unnecessary cardiac monitoring and repeat ECGs.

QT prolongation and torsades de pointes with psychotropic agents

The unexpected and catastrophic cardiovascular effects of psychotropic drugs are well described albeit uncommon. The list of drugs which have been associated with prolonging QT interval and hence potentially causing Torsades de pointes is exhaustive. The insight into the plausible mechanisms are largely unclear. However, the practical implications of anticipating and recognizing QT prolongation cannot be overemphasized.

High dose droperidol and QT prolongation: analysis of continuous 12-lead recordings

AIMS

To investigate the QT interval after high dose droperidol using continuous 12-lead Holter recordings.

METHODS

This was a prospective study of patients given droperidol with a continuous Holter recording. Patients were recruited from the DORM II study which included patients with aggression presenting to the emergency department. Patients initially received 10 mg droperidol as part of a standardized sedation protocol. An additional 10 mg dose was given after 15 min if required and further doses at the clinical toxicologist's discretion. Continuous 12-lead Holter recordings were obtained for 2-24 h utilizing high resolution digital recordings with automated QT interval measurement. Electrocardiograms were extracted hourly from Holter recordings. The QT interval was plotted against heart rate (HR) on the QT nomogram to determine if it was abnormal. QTc F (Fridericia's HR correction) was calculated and >500 ms was defined as abnormal.

RESULTS

Forty-six patients had Holter recordings after 10-40 mg droperidol and 316 QT-HR pairs were included. There were 32 abnormal QT measurements in four patients, three given 10 mg and one 20 mg. In three of the four patients QTc F >500 ms but only in one taking methadone was the timing of QTc F >500 ms consistent with droperidol dosing. Of the three other patients, one took amphetamines, one still had QT prolongation 24 h after droperidol and one took a lamotrigine overdose. No patient given >30 mg had a prolonged QT. There were no arrhythmias.

CONCLUSION

QT prolongation was observed with high dose droperidol. However, there was little evidence supporting droperidol being the cause and QT prolongation was more likely due to pre-existing conditions or other drugs.

Risk assessment of drug-induced QT prolongation

Drugs can cause prolongation of the QT interval, alone or in combination, potentially leading to fatal arrhythmias such as torsades de pointes. When prescribing drugs that prolong the QT interval, the balance of benefit versus harm should always be considered. Readouts from automated ECG machines are unreliable. The QT interval should be measured manually. Changes in heart rate influence the absolute QT interval. Heart rate correction formulae are inaccurate, particularly for fast and slow heart rates. The QT nomogram, a plot of QT interval versus heart rate, can be used as a risk assessment tool to detect an abnormal QT interval.

Risk factors for QT prolongation associated with acute psychotropic drug overdose

BACKGROUND

Antipsychotic/Antidepressant use is a risk factor for QT interval (QT) prolongation and sudden cardiac death. However, it is unclear which drugs are risk factors for QT prolongation and torsades de pointes in cases of psychotropic drug overdose.

METHODS

After correction of QT data by Bazett formula (QTc), QTc was classified into 3 categories (QTc<440 milliseconds, 440 milliseconds≤QTc<500 milliseconds, and QTc≥500 milliseconds), and the blood concentration of each drug was classified as not detected, therapeutic range, or toxic range. The association of the blood concentration of each drug with QTc was analyzed using the ordinal logistic regression model. Drugs that induced QT-heart rate pairs higher than the at-risk line of Isbister's QT-heart rate nomogram (QT nomogram) were further analyzed using the binomial logistic regression model.

RESULTS

A total of 649 patients were enrolled in the study. The independent risk factors for QTc prolongation were therapeutic and toxic range of phenotiazine antipsychotic drug (therapeutic range: odds ratio [OR], 1.56 [P=.039]; toxic range: OR, 3.85 [P<.001]), and toxic range of cyclic antidepressants (OR, 2.39; P=.018). In addition, toxic range of phenotiazine antipsychotic drug (OR, 3.87; P=.012) and tricyclic antidepressants (OR, 4.94; P<.001) were risk factors for QT higher than the at-risk line of the QT nomogram.

CONCLUSIONS

The possibility of QT prolongation and torsades de pointes due to overdose of phenotiazine antipsychotic drug or tricyclic antidepressants requires particular consideration.

Disease-associated QT-shortage versus quinine associated QT-prolongation: age dependent ECG-effects in Ghanaian children with severe malaria

Background

While several anti-malarials are known to affect the electric conduction system of the heart, less is known on the direct effects of Plasmodium falciparum infection. Some earlier studies point to a direct impact of Plasmodium falciparum infection on the electric conduction system of the heart. The aim of this study was to analyse infection- and drug-induced effects on the electric conduction system.

Methods

Children aged 12 months to 108 months with severe malaria were included in Kumasi, Ghana. In addition to basic demographic, clinical, biochemical and parasitological, biochemical data were measured data upon hospitalization (day 0) and 12-lead electrocardiograms were recorded before (day 0) and after (day 1) initiation of quinine therapy as well as after 42 (±3) days.

Results

A total of 180 children were included. Most children were tachycardic on day 0 but heart rate declined on day 1 and during follow up. The corrected QT intervals were longest on day 1 and shortest on day 0. Comparison of QT intervals with day 42 (healthy status) after stratification for age demonstrated that in the youngest (<24 months) this was mainly due to a QT shortage on day 0 while a QT prolongation on day 1 was most pronounced in the oldest (≥48 months). Nearly one third of the participating children had measurable 4-aminoquinoline levels upon admission, but no direct effect on the corrected QT intervals could be shown.

Conclusion

Severe P. falciparum infection itself can provoke changes in the electrophysiology of the heart, independent of anti-malarial therapy. Especially in young - thus non immune - children the effect of acute disease associated pre-treatment QT-shortage is more pronounced than quinine associated QT-prolongation after therapy. Nevertheless, neither malaria nor anti-malarial induced effects on the electrophysiology of the heart were associated with clinically relevant arrhythmias in the present study population.

Intralipid therapy does not improve level of consciousness in overdoses with sedating drugs: a case series

OBJECTIVE

To assess the effect of intralipid emulsion therapy (ILE) in sedating drugs presenting to an urban emergency department.

METHODS

Following the introduction of a clinical protocol for the use of ILE a retrospective chart review was undertaken, which describes the use of ILE in treating sedating drug overdose in a facility with a tertiary referral level clinical toxicology unit. Demographic data as well as details of drug ingested, physiological parameters and disposition were extracted from the medical record.

RESULTS

Over a 7 month period nine cases were treated with intralipid, of which two were male and the median age was 33 years (17-52 years). Endotracheal intubation was required in seven cases and of the other two, one required a nasopharyngeal airway for several hours while being observed in a critical care area. One patient was managed in the intensive care unit without intubation. The median duration of ventilation in the seven patients was 31 h (22-82 h), and median length of stay for all nine cases was 63 h (24-133 h).

CONCLUSION

This study does not support any clinically significant effect of intralipid in sedating drug overdose.

Implementation of warnings from Dear Doctor Letters (Rote-Hand-Briefe): an analysis of medication data from a large cohort of elderly patients

BACKGROUND

Dear Doctor Letters (also known as Direct Healthcare Professional Communications) inform physicians about significant newly discovered drug risks and about measures to take to reduce these risks. How far these warnings actually influence prescribing behavior is unclear.

METHOD

The Geriatrics in Bavaria-Database (GiB-DAT, Geriatrie in Bayern Datenbank) collects data from more than 50 centers offering inpatient geriatric health care. Based on GiB-DAT data, the discharge medication of 76 568 patients (81 ± 8 years, 67% women) was recorded in a standardized manner and analyzed for the implementation of information contained in two Dear Doctor Letters about the risks of dose-related or drug interaction-related QT interval prolongation caused by citalopram or escitalopram.

RESULTS

Patients were discharged with a median of 8 drugs. In the four quarters of 2012 following release of the Dear Doctor Letters, in comparison to the four quarters before their publication, a marked drop from 9.8% to 4.1% was seen in prescriptions for >20 mg/day citalopram--a dosage no longer recommended in elderly patients--and a similar drop from 23.6% to 12.8% in prescriptions for >10 mg/day escitalopram (p<0.0001). Co-prescription of either of these two drugs with other QT interval-prolonging drugs, which was now contraindicated, remained almost unchanged (citalopram: 19.3% [95% confidence interval (CI): 17.9-20.9%] versus 18.4% [95% CI: 17.0-19.8%]; escitalopram: 17.6% [95% CI: 15.8-19.6%] versus 17.1% [95% CI: 14.5-19.9%]).

CONCLUSION

Simple information in Dear Doctor Letters, such as a reduction of the maximum daily dose, was better implemented than complicated information regarding contraindicated co-medication. Quality assurance systems such as the GiB-DAT network make it possible to identify problems of this kind. Licensing authorities and pharmaceutical companies should should improve the clinical usability, e.g., by providing official reference lists of drugs with safety warnings.

Chronic idiopathic nausea

Chronic nausea is a prevalent but poorly described symptom in adolescents. It often co-occurs with other functional gastrointestinal disorders (FGIDs) but may also present in isolation. A multitude of triggers and complex neural pathways underlie the sensation of nausea. These include gastrointestinal and blood-borne insults, dysmotility, vestibular or central nervous system pathways, an aberrant autonomic nervous system, and psychosocial factors. Although clinical algorithms are lacking, diagnosis is typically made on the basis of a thorough clinical history and without extensive testing. Treatment is mainly empiric and may be directed at comorbid symptoms such as migraine, delayed gastric emptying, orthostatic intolerance, and visceral hypersensitivity. Chronic idiopathic nausea is an increasingly prevalent symptom that needs careful clinical assessment and individualized treatment plans.

Heart rate-corrected QT interval predicts mortality in glyphosate-surfactant herbicide-poisoned patients

BACKGROUND

Glyphosate-surfactant herbicide is promoted by the manufacturer as having no risks to human health. Glyphosate surfactant has recently been used with increasing frequency in suicide attempts, so clinical toxicologists occasionally encounter cases of severe systemic toxicity. The purpose of this study was to identify the early predictive factors of patients at risk for mortality and the usefulness of the corrected QT interval (QTc interval) for predicting mortality from glyphosate-surfactant intoxication.

METHODS

This was a retrospective cohort study conducted from January 2005 to December 2012. A total of 153 patients with acute glyphosate-surfactant ingestion were included. To identify the predictive factors for mortality, objective variables easily assessed at presentation including previously reported predictive factors for mortality and severity were retrospectively analyzed for their association with mortality using univariate and multiple logistic analyses.

RESULTS

The average age of the patients was 56 years (range, 19-93 years). Of the 153 patients, 19 (12.4%) died. The most common abnormal electrocardiogram findings were prolonged QTc interval followed by intraventricular conduction delay and first-degree atrioventricular block. Nonsurvivors had a significantly more prolonged QTc interval when compared with that of survivors (survivors: 453.4 ± 33.6 milliseconds vs nonsurvivors: 542 ± 32.0 milliseconds, P < .001). Corrected QT interval and age were associated with a significantly increased risk of death in a multiple logistic regression. In a receiver operating curve analysis, the QTc interval had significant discriminatory power.

CONCLUSION

Prolonged QTc interval seems to be a useful prognostic factor for mortality in patients intoxicated with glyphosate-surfactant herbicide.

Cisplatin-induced bradycardia and the importance of the QT interval

Cisplatin is a very common chemotherapeutic agent used in the treatment of gynecologic malignancies, including cervical, ovarian, and endometrial cancers. Bradycardia is a rare, though potentially severe, side effect of this medication. Here we present the case of a young woman with ovarian cancer who demonstrated significant short-lived cardiotoxicity associated with cisplatin treatment.

Vandetanib in advanced medullary thyroid cancer: review of adverse event management strategies

Introduction

Vandetanib has recently demonstrated clinically meaningful benefits in patients with unresectable, locally advanced or metastatic medullary thyroid cancer (MTC). Given the potential for long-term vandetanib therapy in this setting, in addition to treatment for disease-related symptoms, effective management of related adverse events (AEs) is vital to ensure patient compliance and maximize clinical benefit with vandetanib therapy.

Methods

This expert meeting-based review aims to summarize published data on AEs associated with vandetanib therapy and to provide clinicians with specific practical guidance on education, monitoring, and management of toxicities induced in patients treated with vandetanib in advanced and metastatic MTC. The content of this review is based on the expert discussions from a multidisciplinary meeting held in October 2012.

Results

Characteristics, frequency, and risk data are outlined for a number of dermatological, cardiovascular, gastrointestinal, and general AEs related to vandetanib treatment. Preventive strategies, practical treatment suggestions, and points for clinical consideration are provided.

Conclusions

Good patient and team communication is necessary for the prevention, early detection, and management of AEs of vandetanib. Physicians, nurses, and other healthcare providers play a critical role in providing AE management and patient support to optimize outcomes with vandetanib in MTC.