Drug-induced long QT syndrome in women: review of current evidence and remaining gaps

Sex-related similarities and differences in responses to heart failure therapies

Although sex-related differences in the epidemiology, risk factors, clinical characteristics and outcomes of heart failure are well known, investigations in the past decade have shed light on an often overlooked aspect of heart failure: the influence of sex on treatment response. Sex-related differences in anatomy, physiology, pharmacokinetics, pharmacodynamics and psychosocial factors might influence the response to pharmacological agents, device therapy and cardiac rehabilitation in patients with heart failure. In this Review, we discuss the similarities between men and women in their response to heart failure therapies, as well as the sex-related differences in treatment benefits, dose-response relationships, and tolerability and safety of guideline-directed medical therapy, device therapy and cardiac rehabilitation. We provide insights into the unique challenges faced by men and women with heart failure, highlight potential avenues for tailored therapeutic approaches and call for sex-specific evaluation of treatment efficacy and safety in future research.

A polygenic risk score for the QT interval is an independent predictor of drug-induced QT prolongation

Drug-induced QT prolongation (diLQTS), and subsequent risk of torsade de pointes, is a major concern with use of many medications, including for non-cardiac conditions. The possibility that genetic risk, in the form of polygenic risk scores (PGS), could be integrated into prediction of risk of diLQTS has great potential, although it is unknown how genetic risk is related to clinical risk factors as might be applied in clinical decision-making. In this study, we examined the PGS for QT interval in 2500 subjects exposed to a known QT-prolonging drug on prolongation of the QT interval over 500ms on subsequent ECG using electronic health record data. We found that the normalized QT PGS was higher in cases than controls (0.212±0.954 vs. -0.0270±1.003, P = 0.0002), with an unadjusted odds ratio of 1.34 (95%CI 1.17-1.53, P<0.001) for association with diLQTS. When included with age and clinical predictors of QT prolongation, we found that the PGS for QT interval provided independent risk prediction for diLQTS, in which the interaction for high-risk diagnosis or with certain high-risk medications (amiodarone, sotalol, and dofetilide) was not significant, indicating that genetic risk did not modify the effect of other risk factors on risk of diLQTS. We found that a high-risk cutoff (QT PGS ≥ 2 standard deviations above mean), but not a low-risk cutoff, was associated with risk of diLQTS after adjustment for clinical factors, and provided one method of integration based on the decision-tree framework. In conclusion, we found that PGS for QT interval is an independent predictor of diLQTS, but that in contrast to existing theories about repolarization reserve as a mechanism of increasing risk, the effect is independent of other clinical risk factors. More work is needed for external validation in clinical decision-making, as well as defining the mechanism through which genes that increase QT interval are associated with risk of diLQTS.

Sex Differences in Cardiovascular Management: A Call for Better Acknowledgment-Part 1 Pharmacological Differences in Women and Men; How Relevant Are They?

BACKGROUND

Sex differences (SDs) in pharmacology of cardiovascular (CV) drugs have been described previously; however, paradoxically, there are scarce recommendations in therapy based on these differences. It is of utmost importance to identify whether these SDs determine a modified clinical response and the potential practical implications for this, to provide a base for personalized medicine.

AREA OF UNCERTAINTY

The aim of this article was to outline the most important pharmacological drivers of cardiovascular drugs that differ between women and men, along with their implications and challenges in clinical practice.

DATA SOURCES

A detailed assessment of English-written resources reflecting SDs impact in CV drug pharmacology was performed using PubMed and Embase databases.

RESULTS

Despite large variations in CV drug pharmacokinetics and pharmacodynamics in individuals, correcting for height, weight, surface area, and body composition compensate for most "sex-dependent" differences. In addition, individual, cultural, and social factors significantly impact disease management in women versus men. Gender-biased prescribing patterns and gender-dependent adherence to therapy also influence outcomes. The development of sex-specific guidelines requires that they should reflect the SDs implications for the management of a disease and that the evidence should be carefully evaluated as to whether there is an adequate representation of both sexes and whether sex-disaggregated data are reported.

CONCLUSIONS

Pharmacological drivers are under the influence of an impressive number of differences between women and men. However, to establish their significance in clinical practice, an adequate representation of women in studies and the reporting of distinct results is mandatory.

Practical solutions for including sex as a biological variable (SABV) in preclinical neuropsychopharmacological research

Recently, many funding agencies have released guidelines on the importance of considering sex as a biological variable (SABV) as an experimental factor, aiming to address sex differences and avoid possible sex biases to enhance the reproducibility and translational relevance of preclinical research. In neuroscience and pharmacology, the female sex is often omitted from experimental designs, with researchers generalizing male-driven outcomes to both sexes, risking a biased or limited understanding of disease mechanisms and thus potentially ineffective therapeutics. Herein, we describe key methodological aspects that should be considered when sex is factored into in vitro and in vivo experiments and provide practical knowledge for researchers to incorporate SABV into preclinical research. Both age and sex significantly influence biological and behavioral processes due to critical changes at different timepoints of development for males and females and due to hormonal fluctuations across the rodent lifespan. We show that including both sexes does not require larger sample sizes, and even if sex is included as an independent variable in the study design, a moderate increase in sample size is sufficient. Moreover, the importance of tracking hormone levels in both sexes and the differentiation between sex differences and sex-related strategy in behaviors are explained. Finally, the lack of robust data on how biological sex influences the pharmacokinetic (PK), pharmacodynamic (PD), or toxicological effects of various preclinically administered drugs to animals due to the exclusion of female animals is discussed, and methodological strategies to enhance the rigor and translational relevance of preclinical research are proposed.

Association between exposure to Efavirenz and substrates of dysrhythmia in HIV-infected young adults

Background

Dysrhythmia and sudden cardiac arrest occur more likely in HIV patients than healthy subjects. Thus, we need to examine dysrhythmias adverse effects of medications including Efavirenz as early as possible especially in young subjects.

Hypothesis

Efavirenz might have contributed to increased risk of developing common types of dysrhythmia in young HIV infected patients.

Methods

We performed a retrospective cohort study among 62 patients on Efavirenz and 38 controls. All participants were under 40 years old without cardiovascular disease. Total significant dysrhythmia in 24‐hour ECG monitoring was the primary endpoint determined as the composite of high premature ventricular contraction (PVC) (>500 beats per 24 hours), high premature atrial contraction (PAC) (>500 bp24h), sinus pause, atrioventricular blocks, ventricular tachycardia, prolonged QTc, and low heart rate variability (HRV). Modified composite dysrhythmia consisted of low HRV (SD of normal‐to‐normal [SDNN]), high PVC and prolonged QT.

Results

Mean heart rate, Efavirenz regimen, male gender, and CD4 count predicted total dysrhythmia. Odds ratios were 1.108, 2.90, 4.36, and 0.96, respectively. The incidence of total dysrhythmia, high PVC, high PAC, low HRV(SDNN), and prolonged QTc were 54.8%, 41.85%, 9.71%, 45.2%, and 12.9% in patients on Efavirenz against 42.11%, 31.64%, 0%, 34.2%, and 7.91% in controls, respectively (p‐values: .031, .001, <.0001, .063, and .043 respectively). Modified composite dysrhythmia was also more frequent in Efavirenz group than that of control group (69.42% vs. 52.60%, respectively p = .032).

Conclusions

We found that patients with Efavirenz had higher prevalence of frequent PVC, frequent PAC, total significant dysrhythmia, Low HRV and prolonged QTc than controls.

Sex and Heart Failure Treatment Prescription and Adherence

Heart disease is the leading cause of death in both men and women in developed countries. Heart failure (HF) contributes to significant morbidity and mortality and continues to remain on the rise. While advances in pharmacological therapies have improved its prognosis, there remain a number of unanswered questions regarding the impact of these therapies in women. Current HF guidelines recommend up-titration of neurohormonal blockade, to the same target doses in both men and women but several factors may impair achieving this goal in women: more adverse drug reactions, reduced adherence and even lack of evidence on the optimal drug dose. Systematic under-representation of women in cardiovascular drug trials hinders the identification of sex differences in the efficacy and safety of cardiovascular medications. Women are also under-represented in device therapy trials and are 30% less likely to receive a device in clinical practice. Despite presenting with fewer ventricular arrythmias and having an increased risk of implant complications, women show better response to resynchronization therapy, with lower mortality and HF hospitalizations. Fewer women receive advanced HF therapies. They have a better post-heart transplant survival compared to men, but an increased immunological risk needs to be acknowledged. Technological advances in mechanical circulatory support, with smaller and more hemocompatible devices, will likely increase their implantation in women. This review outlines current evidence regarding sex-related differences in prescription, adherence, adverse events, and prognostic impact of the main management strategies for HF.

Role of Pharmacogenetics in Adverse Drug Reactions: An Update towards Personalized Medicine

Adverse drug reactions (ADRs) are an important and frequent cause of morbidity and mortality. ADR can be related to a variety of drugs, including anticonvulsants, anaesthetics, antibiotics, antiretroviral, anticancer, and antiarrhythmics, and can involve every organ or apparatus. The causes of ADRs are still poorly understood due to their clinical heterogeneity and complexity. In this scenario, genetic predisposition toward ADRs is an emerging issue, not only in anticancer chemotherapy, but also in many other fields of medicine, including hemolytic anemia due to glucose-6-phosphate dehydrogenase (G6PD) deficiency, aplastic anemia, porphyria, malignant hyperthermia, epidermal tissue necrosis (Lyell's Syndrome and Stevens-Johnson Syndrome), epilepsy, thyroid diseases, diabetes, Long QT and Brugada Syndromes. The role of genetic mutations in the ADRs pathogenesis has been shown either for dose-dependent or for dose-independent reactions. In this review, we present an update of the genetic background of ADRs, with phenotypic manifestations involving blood, muscles, heart, thyroid, liver, and skin disorders. This review aims to illustrate the growing usefulness of genetics both to prevent ADRs and to optimize the safe therapeutic use of many common drugs. In this prospective, ADRs could become an untoward "stress test," leading to new diagnosis of genetic-determined diseases. Thus, the wider use of pharmacogenetic testing in the work-up of ADRs will lead to new clinical diagnosis of previously unsuspected diseases and to improved safety and efficacy of therapies. Improving the genotype-phenotype correlation through new lab techniques and implementation of artificial intelligence in the future may lead to personalized medicine, able to predict ADR and consequently to choose the appropriate compound and dosage for each patient.

QTc Prolongation Risk Evaluation in Female COVID-19 Patients Undergoing Chloroquine and Hydroxychloroquine With/Without Azithromycin Treatment

Women have higher risk for developing TdP in response to ventricular repolarization prolonging drugs. Hundreds of trials are administering chloroquine and hydroxychloroquine with/without azithromycin to COVID-19 patients. While an overall prolonged QTc has been reported in COVID-19 patients undergoing these treatments, the question on even higher QTc elevation risk in thousands of female COVID-19 patients undergoing these treatments remains unanswered. We therefore explore data reported and shared with us to evaluate safety and efficacy of antimalaria pharmacotherapies in female COVID-19 patients. Although we observed longer mean QTc intervals in female patients in 2 of the 3 cohorts reviewed, the sex disproportionality in COVID-19 hospitalizations precludes a clear sex mediated QTc interval elevation risk association in the female COVID-19 patients undergoing acute treatment regimens. Adoption of study designs that include observation of sex mediated differential triggering of cardiac electrical activity by these drugs is warranted.

Involvement of sex hormonal regulation of K+ channels in electrophysiological and contractile functions of muscle tissues

Sex hormones, such as testosterone, progesterone, and 17β-estradiol, control various physiological functions. This review focuses on the sex hormonal regulation of K⁺ channels and the effects of such regulation on electrophysiological and contractile functions of muscles. In the cardiac tissue, testosterone and progesterone shorten action potential, and estrogen lengthens QT interval, a marker of increased risk of ventricular tachyarrhythmias. We have shown that testosterone and progesterone in physiological concentration activate KCNQ1 channels via membrane-delimited sex hormone receptor/eNOS pathways to shorten the action potential duration. Mitochondrial K⁺ channels are also involved in the protection of cardiac muscle. Testosterone and 17β-estradiol directly activate mitochondrial inner membrane K⁺ channels (Ca²⁺ activated K⁺ channel (K_Ca channel) and ATP-sensitive K⁺ channel (K_ATP channel)) that are involved in ischemic preconditioning and cardiac protection. During pregnancy, uterine blood flow increases to support fetal growth and development. It has been reported that 17β-estradiol directly activates large-conductance Ca²⁺-activated K⁺ channel (BK_Ca channel) attenuating arterial contraction. Furthermore, 17β-estradiol increases expression of BK_Ca channel β1 subunit which enhances BK_Ca channel activity by DNA demethylation. These findings are useful for understanding the mechanisms of sex or generation-dependent differences in the physiological and pathological functions of muscles, and the mechanisms of drug actions.

Sex Differences in Poisonings Among Older Adults: An Analysis of the Toxicology Investigators Consortium (ToxIC) Registry, 2010 to 2016

PURPOSE

Adults aged >65 years are susceptible to intentional and unintentional poisoning, with contributing factors that include polypharmacy, comorbidity, susceptibility to medication error, and gaps in research. Although toxicologists are often tasked with managing and preventing poisoning among older adults, little is known about sex differences in these poisonings. The aim of this study was to review sex differences in poisonings among older adults managed at the bedside by medical toxicologists.

METHODS

All case subjects aged >65 years in the Toxicology Investigators Consortium (ToxIC) registry between January 2010 and December 2016 were reviewed. Data included reasons for exposure and consultation, exposure agents and routes, presenting clinical findings, and treatment provided. Cases missing age, sex, or primary reason for toxicology consultation data were excluded. We used χ² tests to assess differences in distribution of study variables according to participant sex.

FINDINGS

Among 51,441 total registry cases, 542 (1.05%) were excluded because of missing data. Among the remaining 50,899 cases, 2930 (5.8%) were included for age >65 years; 52.3% of older adults were female. Race was missing or unknown for 49.2% of cases. Adverse drug reactions were more commonly encountered in female subjects than in their male counterparts (9.6% vs 6.4%; P = 0.001). No statistically significant sex differences were observed for total numbers of intentional, unintentional pharmaceutical, and nonpharmaceutical exposures. The most common medications involved were cardiovascular (16.8%) and analgesics/opioids (14.8%). Female subjects were more likely than male subjects to be evaluated by a toxicologist for cardiovascular medications (18.7% vs 14.7%; P = 0.004) and analgesics/opioids (17.6% vs 11.8%; P < 0.001). Male subjects were more likely than female subjects to be evaluated for ethanol toxicity (7.4% vs 1%; P < 0.001) and for envenomations (4.2% vs 1.8%; P < 0.001). The most common route of exposure was oral ingestion (81.3%). Signs/symptoms were noted in 54.8% of cases, with the most common abnormal vital sign being bradycardia (17.2%). Pharmacologic support was the most common intervention and was more common in male subjects than in female subjects (17.7% vs 12.3%; P < 0.001). Deaths were reported in 38 female subjects (2.45%) and 46 male subjects (3.34%); there was no statistically significant difference in death rate according to sex (P = 0.148).

IMPLICATIONS

Older female adults were more commonly evaluated by a medical toxicologist for an adverse drug reaction than older male adults. Female patients were more likely than male patients to be evaluated for poisoning related to analgesic/opioids and cardiovascular medications, and older male patients more frequently received pharmacologic support than older female patients. No significant sex differences were observed in numbers of toxicology consultations for intentional, unintentional pharmaceutical, and nonpharmaceutical exposures.

Serum magnesium and cardiovascular mortality in peritoneal dialysis patients: a 5-year prospective cohort study

The aim of this study was to explore the association between serum Mg and cardiovascular mortality in the peritoneal dialysis (PD) population. This prospective cohort study included prevalent PD patients from a single centre. The primary outcome of this study was cardiovascular mortality. Serum Mg was assessed at baseline. A total of 402 patients (57 % male; mean age 49·3±14·9 years) were included. After a median of 49·9 months (interquartile range: 25·9-68·3) of follow-up, sixty-two patients (25·4 %) died of CVD. After adjustment for conventional confounders in multivariate Cox regression models, being in the lower quartile for serum Mg level was independently associated with a higher risk of cardiovascular mortality, with hazards ratios of 2·28 (95 % CI 1·04, 5·01), 1·41 (95 % CI 0·63, 3·16) and 1·62 (95 % CI 0·75, 3·51) for the lowest, second and third quartiles, respectively. A similar trend was observed when all-cause mortality was used as the study endpoint. Further analysis showed that the relationships between lower serum Mg and higher risk of cardiovascular and all-cause mortality were present only in the female subgroup, and not among male patients. The test for interaction indicated that the associations between lower serum Mg and cardiovascular and all-cause mortality differed by sex (P=0·008 and P=0·011, respectively). In conclusion, lower serum Mg was associated with a higher risk of cardiovascular and all-cause mortality in the PD population, especially among female patients.

Sex as a Biological Variable in Emergency Medicine Research and Clinical Practice: A Brief Narrative Review

The National Institutes of Health recently highlighted the significant role of sex as a biological variable (SABV) in research design, outcome and reproducibility, mandating that this variable be accounted for in all its funded research studies. This move has resulted in a rapidly increasing body of literature on SABV with important implications for changing the clinical practice of emergency medicine (EM). Translation of this new knowledge to the bedside requires an understanding of how sex-based research will ultimately impact patient care. We use three case-based scenarios in acute myocardial infarction, acute ischemic stroke and important considerations in pharmacologic therapy administration to highlight available data on SABV in evidence-based research to provide the EM community with an important foundation for future integration of patient sex in the delivery of emergency care as gaps in research are filled.

Sex hormonal regulation of cardiac ion channels in drug-induced QT syndromes

Female sex is an independent risk factor for development of torsade de pointes (TdP) arrhythmias not only in congenital long QT syndromes but also in acquired long QT syndromes. Clinical and experimental evidences suggest that the gender differences may be due to, at least in part, gender differences in regulation of rate-corrected QT (QT_C) interval between men and women. In adult women, both QT_C interval and arrhythmic risks in TdP alter cyclically during menstrual cycle, suggesting a critical role of female sex hormones in cardiac repolarization process. These gender differences in fundamental cardiac electrophysiology result from variable ion channel expression and diverse sex hormonal regulation via long term genomic and acute non-genomic actions, and sex differences in drug responses and metabolisms. In particular, non-genomic actions of testosterone and progesterone on cardiac ion channels are likely to contribute to the gender differences in cardiac repolarization processes. This review summarizes current knowledge on sex hormonal regulation of cardiac ion channels which contribute to cardiac repolarization processes and its implication for gender differences in drug-induced long QT syndromes.

Sex and the Lab: An Alcohol-Focused Commentary on the NIH Initiative to Balance Sex in Cell and Animal Studies

In May 2014, Dr. Francis Collins, the director of U.S. National Institutes of Health (NIH), and Dr. Janine Clayton, the director of the U.S. National Institutes of Health Office of Research on Women's Health, published a commentary in the journal Nature announcing new policies to ensure that preclinical research funded by the NIH considers both males and females. While these policies are still developing, they have already generated great interest by the scientific community and triggered both criticism and applause. This review provides a description and interpretation of the NIH guidelines, and it traces the history that led to their implementation. As expected, this NIH initiative generated some anxiety in the scientific community. The use of female animals in the investigation of basic mechanisms is perceived to increase variability in the results, and the use of both sexes has been claimed to slow the pace of scientific discoveries and to increase the cost at a time characterized by declining research support. This review discusses issues related to the study of sex as a biological variable (SABV) in alcohol studies and provides examples of how researchers have successfully addressed some of them. A practical strategy is provided to include both sexes in biomedical research while maintaining control of the research direction. The inclusion of sex as an important biological variable in experimental design, analysis, and reporting of preclinical alcohol research is likely to lead to a better understanding of alcohol pharmacology and the development of alcohol use disorder, may promote drug discovery for new pharmacotherapies by increasing scientific rigor, and may provide clinical benefit to women's health. This review aims to promote the understanding of the NIH's SABV guidelines and to provide alcohol researchers with a theoretical and practical framework for working with both sexes in preclinical research.

Acute toluene intoxication--clinical presentation, management and prognosis: a prospective observational study

Background

Toluene is one of the most widely abused inhaled drugs due to its acute neurologic effects including euphoria and subsequent depression. However, dangerous metabolic abnormalities are associated to acute toluene intoxication. It has been previously reported that rhabdomyolysis and acute hepatorenal injury could be hallmarks of the condition, and could constitute risk factors for poor outcomes. The objective was to describe the clinical presentation, to characterize the renal and liver abnormalities, the management and prognosis associated to acute toluene intoxication.

Methods

We prospectively assessed 20 patients that were admitted to a single center’s emergency department from September 2012 to June 2014 with clinical and metabolic alterations due to acute toluene intoxication.

Results

The main clinical presentation consisted of weakness associated to severe hypokalemia and acidosis. Renal glomerular injury (proteinuria) is ubiquitous. Biliary tract injury (alkaline phosphatase and gamma-glutamyl transpeptidase elevations) disproportional to hepatocellular injury is common. Rhabdomyolysis occurred in 80 % of patients, probably due to hypokalemia and hypophosphatemia. There were three deaths, all female, and all associated with altered mental status, severe acidosis, hypokalemia and acute oliguric renal failure. The cause of death was in all cases due to cardiac rhythm abnormalities.

Conclusion

The hallmarks of acute toluene intoxication are hypokalemic paralysis and metabolic acidosis. Liver injury and rhabdomyolysis are common. On admission, altered mental status, renal failure, severe acidemia and female gender (not significant in our study, but present in all three deaths) could be associated with a poor outcome, and patients with these characteristics should be considered to be treated in an intensive care unit.

Drug-induced proarrhythmia: risk factors and electrophysiological mechanisms

Drug-induced ventricular tachyarrhythmias can be caused by cardiovascular drugs, noncardiovascular drugs, and even nonprescription agents. They can result in arrhythmic emergencies and sudden cardiac death. If a new arrhythmia or aggravation of an existing arrhythmia develops during therapy with a drug at a concentration usually considered not to be toxic, the situation can be defined as proarrhythmia. Various cardiovascular and noncardiovascular drugs can increase the occurrence of polymorphic ventricular tachycardia of the 'torsade de pointes' type. Antiarrhythmic drugs, antimicrobial agents, and antipsychotic and antidepressant drugs are the most important groups. Age, female sex, and structural heart disease are important risk factors for the occurrence of torsade de pointes. Genetic predisposition and individual pharmacodynamic and pharmacokinetic sensitivity also have important roles in the generation of arrhythmias. An increase in spatial or temporal dispersion of repolarization and a triangular action-potential configuration have been identified as crucial predictors of proarrhythmia in experimental models. These studies emphasized that sole consideration of the QT interval is not sufficient to assess the proarrhythmic risk. In this Review, we focus on important triggers of proarrhythmia and the underlying electrophysiological mechanisms that can enhance or prevent the development of torsade de pointes.

Impact of Age and Sex on QT Prolongation in Patients Receiving Psychotropics

OBJECTIVE

To assess older age and female sex, 2 of the major risk factors for potentially fatal cardiac arrhythmias or sudden cardiac death in patients prescribed psychotropics, within the context of electrocardiographic evidence of time between start of Q wave and end of T wave (QT) interval prolongation, which is an indicator of an increased risk for potentially fatal cardiac arrhythmias.

METHOD

The literature on the relation between age, sex, and QT interval with respect to psychotropic drugs was reviewed.

RESULTS

The QT interval must be corrected (QTc) for heart rate. Because slower heart rates prolong and faster heart rates shorten the QT interval, people with faster heart rates may have a prolonged QT interval that is not apparent until the correction is performed. QTc values for apparently healthy post-pubertal people are less than 450 ms for males and less than 470 ms for females. The longer QT intervals in women may account for their increased risk of potentially fatal cardiac arrhythmias on psychotropics. QTc increases with increasing age. Assessment of QTc in older people is especially important to identify people with a longer QTc who are more likely to attain a serious QT level with drugs that prolong QTc. The age-related increase in QTc is more evident in men than women, suggesting that male sex does not afford protection against potentially fatal arrhythmias at older age.

CONCLUSION

The association of increasing age and female sex with greater QT intervals indicates the need to have an increased awareness of the QTc prior to use of these psychotropics and to evaluate the QTc after initiation of therapy.

Determinants of torsades de pointes in older patients with drug-associated long QT syndrome: a case-control study

OBJECTIVE

Many elderly patients are routinely exposed to drugs that may prolong the cardiac QT interval and cause Torsades de pointes (TdP). However, predictors of TdP in patients with drug-associated long QT syndrome (LQTS) are not fully understood, especially in the geriatric population. The objective of this study was to identify risk factors of TdP in elderly patients with drug-associated LQTS.

METHODS

In this retrospective, case-control study, documented reports of drug-associated LQTS plus TdP (n = 125) and LQTS without TdP (n = 81) in patients ≥65 years of age were retrieved from the French Pharmacovigilance Database over a 10-year period. Available clinical, biological, and drug therapy data were compared in the two groups and logistic regression was performed to identify significant predictors of TdP.

RESULTS

The uncorrected QT interval was significantly longer in patients with TdP than in patients without TdP (577 ± 79 vs. 519 ± 68 ms; p = 0.0001). The number of drugs with a known risk of TdP administered to each patient was not a predictor of arrhythmia, nor was female gender. Logistic regression analysis identified the uncorrected QT interval as the only significant predictor of TdP. The receiver operating characteristic curve analysis was characterized by an area under the curve of 0.77 (95 % confidence interval 0.64-0.88) and a QT cutoff of 550 ms.

CONCLUSION

The uncorrected QT interval was significantly associated with the probability of TdP in elderly patients with acquired, drug-associated LQTS.

Effect of amphetamine on corrected-QT interval change during methadone maintenance treatment in Taiwan: a prospective cohort study

INTRODUCTION AND AIMS

Previous studies have suggested that methadone is associated with prolonged corrected-QT (QTc) interval, but published prospective research studies in this area are relatively scarce. This study investigates QTc interval change among methadone maintenance patients and possible associated risk factors. One of the aims is to explore the effect of amphetamines.

DESIGN AND METHODS

This prospective cohort study with six-month follow up assesses the effect of methadone on QTc interval among a sample (n = 170) of heroin users in a methadone maintenance treatment program in Taiwan. Demographic data, substance use history, medical history and laboratory studies were collected at study enrollment. Twelve-lead electrocardiograms were performed for all participants both at study enrollment and six months later.

RESULTS

The median daily methadone dose was 41 mg. A mean increase of QTc interval (17.1 ms, SD = 50.0, P < 0.001) was found at six-month follow up. QTc interval prolongation in the sample at baseline was 2.9%, and at six months was 12.4%. A positive correlation was found between comorbid amphetamine use frequency in the past month and QTc interval change. Methadone dose was not associated with QTc change.

DISCUSSION AND CONCLUSIONS

An increase of mean QTc interval was found among methadone maintenance patients at six-month follow up. Electrocardiogram monitoring should be performed among patients who are at risk of frequently using amphetamines during methadone maintenance treatment.

Quantitative PCR as an alternative in the diagnosis of long-QT syndrome

Congenital long-QT syndrome is a genetic disorder associated with abnormalities in the function and/or structure of cardiac ion channels. Up to the present, 13 types of the disease have been described (LQTS1-13) which result from the fact that 13 genes of which mutations can have an influence on the occurrence of the disease have been identified. Characteristic symptoms of the disease include the changes in the ECG (QT interval prolonged above 450 ms), "torsade de pointes," fainting, and even sudden cardiac death. The present study has been focused on two types of the disease, namely, LQTS1 and LQTS2. The examination of two appropriate genes expression (KCNQ1; KCNH2) at the transcription level by QRT-PCR in a group of LQTS patients and a healthy control group showed different transcriptional activities of KCNH2 gene in LQTS2 patients compared to the control individuals. KCNQ1 gene expression study did not reveal such differences between both groups. The results indicate that QRT-PCR may serve as a complimentary method to the identification of molecular alterations in genetic determinants of LQTS2 only, but it cannot be used as a sole diagnostic criterion.

Modeling gender effects on electrical activity of single ventricular myocytes

In this study we investigate the mechanisms underlying gender differences in the generation of arrhythmias in the long QT and Brugada syndromes. Simulations were conducted at the single myocyte level using a detailed mathematical model of human ventricular myocytes. Given the scarce human data on the gender-related differences in single cardiac cells, we assumed gender-related differences in five ionic-current systems: fast sodium current (INa), slowly inactivating late sodium current (INal), transient outward potassium current (Ito), slow delayed rectifier potassium current (IKs), and calcium current through the L-type channel (ICa(L)), based on experimental results obtained in canine myocytes. Our modeling results suggest that in left ventricular myocytes, enhanced INal under conditions of reduced repolarization reserve results in sex-dependent development of early afterdepolarizations (EADs) in the post-pause action potentials (APs). Moreover, this modeling study demonstrates increased propensity for the development of the loss of the AP dome in male epicardial myocytes of the right ventricle compared with other types of myocytes from the left and right ventricles. Finally, we also found a slight effect of INal on gender-dependent loss of AP dome in epicardial right ventricular myocytes. In conclusion, at the cellular level, gender differences in the development of EADs and the propensity to develop the loss of the AP dome can be attributed to male/female related differences in INa, INal, Ito, IKs, and ICa(L).

Sex and gender aspects in antiarrhythmic therapy

Although cardiac arrhythmia had long been considered a predominantly male syndrome, it is now clear that arrhythmia is also a primary cause of mortality in women. Notably, the manifestation of specific arrhythmia syndromes appears to be gender specific. In particular, female sex is an independent risk factor for development of torsade de pointes (TdP) arrhythmias not only in congenital long QT syndromes but also in acquired long QT syndromes which occur as adverse effects of existing drugs. Males, on the other hand, are more likely to develop Brugada syndrome. Recent clinical and experimental studies suggest that these differences may stem from intrinsic sex differences in cardiac tissue. These include fundamental electrical differences resulting from variable ion channel expression and diverse sex hormonal regulation via long-term genomic and acute nongenomic pathways, and sex differences in drug responses and metabolisms. Undoubtedly, determining the effect of gender on cardiac function will be difficult and require sophisticated methodologies. However, gender differences underlying predilection to distinct arrhythmia syndromes must be revealed so that new therapeutic strategies that take gender into account can be applied to at-risk patients.

A GENS-based approach to cardiovascular pharmacology: impact on metabolism, pharmacokinetics and pharmacodynamics

Pharmacological outcomes depend on many factors, with many of them being sexually dimorphic. Thus, physiological gender/sex (GENS) differences can influence pharmacokinetics, pharmacodynamics and, thus, bioavailability and resulting in efficacy of treatment, meaning GENS differences should be an important consideration in therapeutics. In particular, drug response can change according to different hormonal environments. Therefore, GENS-specific differences have a particular clinical relevance in terms of drug delivery, especially for those substances with a narrow therapeutic margin. Since adverse effects are more frequent among women, safety is a key issue. Overall, the status of women, from a pharmacological point of view, is often different and less studied than that of men and deserves particular attention. Further studies focused on women's responses to drugs are necessary in order to make optimal pharmacotherapeutic decisions.

Age-and sex-dependent mRNA expression of KCNQ1 and HERG in patients with long QT syndrome type 1 and 2

INTRODUCTION

The main goal of this study was to examine the patient age and sex dependent expression of KCNQ1 and HERG genes that encode potassium channels responsible for the occurrence of long QT syndrome (LQTS).

MATERIAL AND METHODS

The study enrolled 43 families whose members suffered from LQTS type 1 (LQTS1) or 2 (LQTS2) or were healthy. The study attempted to prove that β-actin is a good endogenous control when determining the expression of the studied genes. Examination of gene expression was achieved with quantitative real-time PCR (QRT-PCR). Expression of the investigated genes was inferred from the analysis of the number of mRNA copies per 1 μg total RNA isolated from whole blood.

RESULTS

Significantly lower KCNQ1 and KCNH2 mRNA levels in healthy females than healthy males were observed (p = 0.032; p = 0.02). In male patients both transcripts were expressed at a lower level (p = 0.0084; p = 0.035). The comparison of transcriptional activity of KCNQ1 and KCNH2 in healthy adults and children revealed higher KCNQ1 and lower KCNH2 mRNA levels in healthy adults (p = 0.033; p = 0.04), higher KCNQ1 and lower KCNH2 mRNA levels in adult patients below 55 years old than in adults over 55 years old (p=0.036; p = 0.044), and significantly higher KCNQ1 and lower KCNH2 mRNA levels in adult patients (over 55 years) than in paediatric patients (below 15 years) (p=0.047; p = 0.08).

CONCLUSIONS

The results support the hypothesis that KCNQ1 and HERG gene expression is influenced by age and gender in human patients with long QT syndrome and in healthy subjects.

Drug-induced long QT syndrome

The drug-induced long QT syndrome is a distinct clinical entity that has evolved from an electrophysiologic curiosity to a centerpiece in drug regulation and development. This evolution reflects an increasing recognition that a rare adverse drug effect can profoundly upset the balance between benefit and risk that goes into the prescription of a drug by an individual practitioner as well as the approval of a new drug entity by a regulatory agency. This review will outline how defining the central mechanism, block of the cardiac delayed-rectifier potassium current I(Kr), has contributed to defining risk in patients and in populations. Models for studying risk, and understanding the way in which clinical risk factors modulate cardiac repolarization at the molecular level are discussed. Finally, the role of genetic variants in modulating risk is described.

Aggravation of Arrhythmia by Antiarrhythmic Drugs (Proarrhythmia)

Arrhythmia aggravation by antiarrhythmic drugs (proarrhythmia) can be caused by worsening or a change of a preexisting arrhythmia, development of a new arrhythmia, or development of a bradyarrhythmia. Aggravation of arrhythmia usually occurs within several days of beginning an antiarrhythmic drug or increasing the dose of the drug. The time of occurrence is based on the particular drug and its pharmacokinetic properties. Although there are no ways to predict the patient at risk for developing arrhythmia aggravation with any specific agents, risk factors include QT interval prolongation, elevated serum levels of the drug, electrolyte abnormalities, presence of heart failure, a history of a sustained ventricular tachyarrhythmia, and underlying myocardial ischemia.

Gender differences in drug toxicity

Clinical data suggest that gender dimorphic profiles are emerging in terms of both drug efficacy and adverse drug reactions (ADRs). With an increasing emphasis on individualised therapies and the need to prevent drug attrition there is a compelling need to understand the molecular basis for gender dimorphic profiles in ADRs and the consequences. Classes of agents exhibiting gender-based variation in pharmaceutical efficacy and toxicity include anaesthetics, HIV-1 therapies and antiarrhythmic drugs. Body weight differences are often cited as a reason for differences in drug pharmacokinetics and subsequent toxicity. However, some studies accounted for these factors and still found significance suggesting that dosage versus body weight does not explain the outcome. Here, we present an overview of current understanding of gender-specific drug toxicity and present rational molecular explanations for these adverse events. There is mounting evidence in support of hormonal effects underpinning the majority of the ADR differences observed between the sexes.

Schizophrenia: women bear a disproportionate toll of antipsychotic side effects

BACKGROUND

Men and women with schizophrenia suffer not only from their illness but also from the side effects of their medications.

OBJECTIVE

To review the toll of antipsychotic side effects specifically on women.

STUDY DESIGN

A review of the literature in the PubMed database since 1990 using search terms: sex difference, antipsychotics, schizophrenia, pharmacokinetics, pharmacodynamics, and pharmacogenomics and retrieving additional publications from the reference lists of the original articles.

RESULTS

Findings suggest that, because of differing pharmacokinetics, women are more vulnerable than men to weight gain secondary to antipsychotics and to the consequences (metabolic, cardiovascular, reproductive) of weight gain. They are also more vulnerable to hyperprolactinemia and QTc prolongation.

CONCLUSIONS

Dosing guidelines need to be critically appraised. The greater toll of side effects in women may undermine adherence to prescribed treatments, add to the stigma that attaches to mental illness, and diminish the quality of women's lives. Side effects increase the cost of mental illness and heighten the burden experienced by caregivers. They exacerbate morbidity and raise mortality rates. They affect the children of women treated with antipsychotic medication.