Antiarrhythmic agents: drug interactions of clinical significance

Effectiveness of a Triple Antiarrhythmic Drug Strategy for Arrhythmia Recurrence after Persistent Atrial Fibrillation Ablation

BACKGROUND AND OBJECTIVE

Treating recurrent atrial arrhythmias after persistent atrial fibrillation (PeAF) ablation is often challenging. This single-center, prospective study aimed to observe the effectiveness of different combinations of oral antiarrhythmic drugs (AADs) in reverting to sinus rhythm (SR) in patients with recurrent atrial arrhythmias after PeAF ablation.

METHODS

Forty-five patients who experienced recurrent atrial arrhythmias after PeAF ablation were included. Based on their medication regimens, patients were divided into two groups, with the study group being a triple-drug group (digoxin combined with amiodarone/ propafenone and β-blocker), and the control group being a non-triple-drug group.

RESULTS

The rate of reversion to SR was significantly higher in the study group (n = 29) than in the control group (n = 16) at 3 weeks (34.48% vs. 0%, p < 0.01) and 1 month (44.84% vs. 6.25%, p = 0.02) after initiating AADs. No patients with asymptomatic bradycardia were observed in either group.

CONCLUSIONS

For patients with recurrent atrial arrhythmias after PeAF ablation, a regimen of low-dose digoxin combined with amiodarone/propafenone and β-blocker may effectively improve short-term reversion rates.

Quinidine for ventricular arrhythmias: A comprehensive review

Quinidine, the first antiarrhythmic drug, was widely used during the 20th century. Multiple studies have been conducted to provide insights into the pharmacokinetics and pleiotropic effects of Class Ia antiarrhythmic drugs. However, safety concerns and the emergence of new drugs led to a decline in their use during the 1990s. Despite this, recent studies have reignited the interest in quinidine, particularly for ventricular arrhythmias, where other antiarrhythmics have failed. In conditions such as Brugada syndrome, idiopathic ventricular fibrillation, early repolarization syndrome, short QT syndrome, and electrical storms, quinidine remains a valuable asset. Starting from the European and American recommendations, this comprehensive review aimed to explore the various indications for quinidine and the studies that support its use. We also discuss the potential future of quinidine, including the necessary research to optimize its use and patient selection. Additionally, it addresses the imperative task of mitigating the iatrogenic burden associated with quinidine usage and confronts the challenge of ensuring drug accessibility.

Does Disopyramide Still Have a Place in the Management of Obstructive Hypertrophic Cardiomyopathy?

Hypertrophic cardiomyopathy (HCM) is a relatively common inherited cardiac disorder associated with a left ventricular hypertrophy that cannot be explained by another cardiac or systemic disorder. One of the core pathophysiology features is left ventricular outflow tract obstruction (obstructive HCM [oHCM]), and this pathology could lead to complications, including sudden cardiac death and heart failure. Current treatment strategies for symptomatic oHCM consist of historical pharmacologic agents that are often based on nonrandomized, limited data or expert opinion. This article presents a critical appraisal of disopyramide, one of the pharmacologic options available in Canada for managing oHCM. The author concludes that robust clinical evidence supporting the use of disopyramide in treating oHCM is lacking, and that disopyramide should be reserved as a last resort for nonresponders to pharmacologic treatment and for those in whom invasive therapies are not indicated.

Efficacy and tolerability of desvenlafaxine in the real-world treatment of patients with major depression: a narrative review and an expert opinion paper

INTRODUCTION

Major depressive disorder (MDD) is a common severe mental disorder, requiring a tailored and integrated treatment. Several approaches are available including different classes of antidepressants various psychotherapeutic approaches, and psychosocial interventions. The treatment plan for each patient with MDD should be differentiated on the basis of several clinical, personal, and contextual factors.

AREAS COVERED

Desvenlafaxine - a serotonine-noradrenergic reuptake inhibitor (SNRI) antidepressant - has been approved in the United States in 2008 for the treatment of MDD in adults, and has been recently rediscovered by clinicians due to its good side-effect profile and its clinical effectiveness. A narrative review on efficacy, tolerability and use of desvenlafaxine in clinical practice was carried out. The keywords: 'major depression', 'depression,' 'desvenlafaxine,' 'efficacy,' 'clinical efficacy,' 'side effects', 'tolerability,' 'elderly patients', 'consultation-liaison', 'menopausal', 'young people', 'adolescent' were entered in PubMed, ISI Web of Knowledge, Scopus and Medline. No time limit was fixed, the search strategy was implemented on May 10, 2023.

EXPERT OPINION

Desvenlafaxine should be listed among the optimal treatment strategies for managing people with MDD, whose main strengths are: 1) ease of dosing; 2) favorable safety and tolerability profile, 3) absence of sexual dysfunctions, weight gain and low rate of discontinuation symptoms; 4) low risk of drug-drug interactions.

Natural products as the calcium channel blockers for the treatment of arrhythmia: Advance and prospect

Arrhythmia is one of the commonly heart diseases with observed abnormal heart-beat rhythm that caused by the obstacles of cardiac activity and conduction. The arrhythmic pathogenesis is complex and capricious and related with other cardiovascular diseases that may lead to heart failure and sudden death. In particular, calcium overload is recognized as the main reason causing arrhythmia through inducing apoptosis in cardiomyocytes. Moreover, calcium channel blockers have been widely used as the routine drugs for the treatment of arrhythmia, but the different arrhythmic complications and adverse effects limit their further applications and demand new drug discovery. Natural products have always been the rich minerals for the development of new drugs that could be employed as the versatile player for the discovery of safe and effective anti-arrhythmia drugs with new mechanisms. In this review, we summarized natural products with the activity against calcium signaling and the relevant mechanism of actions. We are expected to provide an inspiration for the pharmaceutical chemists to develop more potent calcium channel blockers for the treatment of arrhythmia.

Perspective on Antiarrhythmic Drug Combinations

Physicians use multiple drugs in combination to treat hypertension, heart failure, diabetes mellitus, angina, hyperlipidemia, and many other cardiovascular conditions and risk factors. However, administering antiarrhythmic drugs (AAD) in combination is rarely discussed. Yet, the possibility of increasing efficacy and/or tolerance and/or safety of AADs (by adding mechanisms, offsetting adverse mechanisms, and/or using lower doses) exists. Unfortunately, this topic has not been reviewed in any contemporary cardiac literature of which we are aware, although information regarding AAD combinations has been published. In conclusion, and accordingly, this review discusses the possibility of using AAD combinations for both ventricular arrhythmias and atrial fibrillation, in which the rationale for such combinations, considerations for such combinations, and supporting literature are covered.

Mental health conditions and use of rhythm control therapies in patients with atrial fibrillation: a nationwide cohort study

OBJECTIVES

Mental health conditions (MHCs) have been associated with undertreatment of unrelated medical conditions, but whether patients with MHCs face disparities in receiving rhythm control therapies for atrial fibrillation (AF) is currently unknown. We assessed the hypothesis that MHCs are associated with a lower use of antiarrhythmic therapies (AATs).

DESIGN

A nationwide retrospective registry-based cohort study.

SETTING

The Finnish AntiCoagulation in Atrial Fibrillation cohort included records on all patients with AF in Finland during 2007-2018 identified from nationwide registries covering all levels of care as well as drug purchases. MHCs of interest were diagnosed depression, bipolar disorder, anxiety disorder, schizophrenia and any MHC.

PARTICIPANTS

We identified 239 222 patients (mean age 72.6±13.2 years; 49.8% women) with incident AF, in whom the prevalence of any MHC was 19.9%.

OUTCOMES

Primary outcome was use of any AAT, including cardioversion, catheter ablation, and fulfilled antiarrhythmic drug (AAD) prescription.

RESULTS

Lower overall use of any AAT emerged in patients with any MHC than in those without MHC (16.9% vs 22.9%, p<0.001). Any MHC, depression, bipolar disorder, anxiety disorder and schizophrenia were all associated with lower incidence of any AAT with adjusted subdistribution HRs of 0.790 (95% CI 0.771 to 0.809), 0.817 (0.796 to 0.838), 0.811 (0.789 to 0.835), 0.807 (0.785 to 0.830) and 0.795 (0.773 to 0.818), respectively. Adjusted rates of AAD, cardioversion and catheter ablation use were lower in all MHC groups compared with patients without MHC. The findings in patients with any MHC were confirmed in propensity score matching analysis.

CONCLUSIONS

Among patients with AF, a clear disparity exists in AAT use between those with and without MHCs.

TRIAL REGISTRATION NUMBER

ClinicalTrials Identifier: NCT04645537; ENCePP Identifier: EUPAS29845.

Drug Interactions Affecting Antiarrhythmic Drug Use

Antiarrhythmic drugs (AAD) play an important role in the management of arrhythmias. Drug interactions involving AAD are common in clinical practice. As AADs have a narrow therapeutic window, both pharmacokinetic as well as pharmacodynamic interactions involving AAD can result in serious adverse drug reactions ranging from arrhythmia recurrence, failure of device-based therapy, and heart failure, to death. Pharmacokinetic drug interactions frequently involve the inhibition of key metabolic pathways, resulting in accumulation of a substrate drug. Additionally, over the past 2 decades, the P-gp (permeability glycoprotein) has been increasingly cited as a significant source of drug interactions. Pharmacodynamic drug interactions involving AADs commonly involve additive QT prolongation. Amiodarone, quinidine, and dofetilide are AADs with numerous and clinically significant drug interactions. Recent studies have also demonstrated increased morbidity and mortality with the use of digoxin and other AAD which interact with P-gp. QT prolongation is an important pharmacodynamic interaction involving mainly Vaughan-Williams class III AAD as many commonly used drug classes, such as macrolide antibiotics, fluoroquinolone antibiotics, antipsychotics, and antiemetics prolong the QT interval. Whenever possible, serious drug-drug interactions involving AAD should be avoided. If unavoidable, patients will require closer monitoring and the concomitant use of interacting agents should be minimized. Increasing awareness of drug interactions among clinicians will significantly improve patient safety for patients with arrhythmias.

Treatments of new-onset atrial fibrillation in critically ill patients: a systematic review with meta-analysis

BACKGROUND

New-onset atrial fibrillation (NOAF) is common in hospitalised patients with critical illness and associated with worse outcomes. Several interventions are available in the management of NOAF, but the overall effectiveness and safety of these interventions compared with placebo or no treatment are unknown.

METHODS

We conducted a systematic review with meta-analysis and trial sequential analysis (TSA) of randomised clinical trials (RCT) in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses, the Cochrane Collaboration, and Grading of Recommendations Assessment, Development and Evaluation statements. We searched RCTs assessing any pharmacological and non-pharmacological treatment compared with placebo or no treatment in critically ill hospitalised patients with NOAF. The primary outcomes were all-cause mortality, adverse events, and health-related quality of life.

RESULTS

We included 16 trials (n = 1891) evaluating seven interventions. All trials were adjudicated 'some concerns' or 'high risk' of bias. The evidence is very uncertain for mortality (RR 0.53, 95% CI 0.03-8.30), adverse events (RR 1.28, 95% CI 0.85-1.92), and treatment efficacy i.e. rhythm control (RR 1.54, 95% CI 1.20-1.97; TSA-adjusted CI 0.56-4.53) between pharmacological treatment and placebo/no treatment (very low certainty evidence). There were no data for health-related quality of life or most of our secondary outcomes.

CONCLUSIONS

The existing data are insufficient to firmly conclude on effects of any intervention against NOAF on any outcome in hospitalised patients with critical illness. Randomised trials of the most frequently used interventions against NOAF are warranted in these patients.

Risk Factors for the Occurrence of Potential Drug-Drug Interactions in Surgical Patients

Background: Drug-drug interactions are defined as modifications of the drug action that result from the simultaneous administration of another individual drug or several drugs. Nowadays, potential drug-drug interactions (DDIs) are most frequently detected and analyzed using personal digital assistant software programs (online interaction checker tools).

Objective: To determine the risk factors for the emergence of all drug-drug interactions in surgical patients with particular emphasis on clinically significant interactions.

Patients and methods: This was a retrospective cohort analysis of patients treated at the Surgical Clinic of the Clinical Center Kragujevac. Three interaction checkers were used to reveal drug-drug interactions: Medscape, Epocrates and Micromedex.

Results: The study included total of 200 patients, aged 58.54±17.08 years. Average number of drug-drug interactions per patient was between 10.50±9.10 (Micromedex) and 18.75±17.14 (Epocrates). Number of prescribed drugs, antidepressive therapy, antiarrhythmic therapy, number of pharmacological/therapeutic subgroups (2nd level of ATC classification) prescribed, delirium or dementia, diabetes, heart failure, and number of physicians who prescribed drugs to single patient were identified as risk factors for drug-drug interactions while length of hospitalization in days and age of patient in years emerged as protective factors.

Conclusion: Drug-drug interactions are relatively common in surgical patients and predisposed by factors such as number of prescribed drugs or drug group per patient, number of physicians who prescribed drugs, antidepressive therapy, antiarrhythmic therapy, presence of delirium or dementia, diabetes and heart failure. On the other hand, prolonged hospitalization and higher age are factors that reduce the risk of interactions in surgical patients.

Effects of 1α,25-Dihydroxyvitamin D3 on the Pharmacokinetics of Procainamide and Its Metabolite N-Acetylprocainamide, Organic Cation Transporter Substrates, in Rats with PBPK Modeling Approach

In this study, possible changes in the expression of rat organic cationic transporters (rOCTs) and rat multidrug and toxin extrusion proteins (rMATEs) following treatment with 1α,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) were investigated. Rats received intraperitoneal administrations of 1,25(OH)₂D₃ for four consecutive days, and the tissues of interest were collected. The mRNA expression of rOCT1 in the kidneys was significantly increased in 1,25(OH)₂D₃-treated rats compared with the control rats, while the mRNA expressions of rOCT2 and rMATE1 in the kidneys, rOCT1 and N-acetyltransferase-II (NAT-II) in the liver, and rOCT3 in the heart were significantly decreased. Changes in the protein expression of hepatic rOCT1 and renal rOCT2 and rMATE1 were confirmed by western blot analysis. We further evaluated the pharmacokinetics of procainamide (PA) hydrochloride and its major metabolite N-acetyl procainamide (NAPA) in the presence of 1,25(OH)₂D₃. When PA hydrochloride was administered intravenously at a dose 10 mg/kg to 1,25(OH)₂D₃-treated rats, a significant decrease in renal and/or non-renal clearance of PA and NAPA was observed. A physiological model for the pharmacokinetics of PA and NAPA in rats was useful for linking changes in the transcriptional and translational expressions of rOCTs and rMATE1 transporters to the altered pharmacokinetics of the drugs.

Safety and Effectiveness of Rivaroxaban in Combination with Various Antiarrhythmic Drugs in Patients with Non-Permanent Atrial Fibrillation

INTRODUCTION

Rivaroxaban reduces the risk of thromboembolism in atrial fibrillation (AF) patients, who often also receive antiarrhythmic drugs (AADs) to maintain sinus rhythm. Current guidelines contraindicate concomitant use of rivaroxaban with the popular AAD dronedarone, despite little data demonstrating interactions with AADs. This study investigates the outcomes of concomitant rivaroxaban and AAD drug use in a real-world cohort.

METHODS

This retrospective study included 1777 non-permanent AF patients taking rivaroxaban for ≥ 1 month between 2011 and 2016 from a multicenter cohort in Taiwan, and compared concomitant AAD use against clinical outcome endpoints for safety, effectiveness, and major adverse cardiac events (MACE). Multivariate Cox proportional hazard analyses were used to evaluate the association between concomitant AAD use and outcomes.

RESULTS

Patients were divided into rivaroxaban alone (n = 1205) and with concomitant amiodarone (n = 177), dronedarone (n = 231), or propafenone (n = 164) groups. The proportion of patients using rivaroxaban 10 mg was highest in the concomitant dronedarone group: rivaroxaban alone, 53.6%; with amiodarone, 57.6%; with dronedarone, 77.1%; and with propafenone, 46.3% (p < 0.001). The cumulative incidences of safety (p = 0.892), effectiveness (p = 0.336), and MACE (p = 0.674) were similar between the four groups; however, there were significantly fewer new systemic thromboembolisms in the dronedarone group: rivaroxaban alone, 2.5%; with amiodarone, 0.6%; with dronedarone, 0%; and with propafenone, 1.2% (p = 0.029). The all-cause death rate was also lowest in the dronedarone group: rivaroxaban alone, 9.0%; with amiodarone, 9.6%; with dronedarone, 3.0%; and with propafenone: 6.1% (p = 0.013). After covariate adjustment, there were no differences in the safety, effectiveness, and MACE endpoints between patients receiving or not receiving AADs.

CONCLUSION

Concomitant use of rivaroxaban with AADs appears to be well tolerated, warranting further investigation into the apparent benefits of a reduced dose of rivaroxaban combined with dronedarone.

Lopinavir-Ritonavir in SARS-CoV-2 Infection and Drug-Drug Interactions with Cardioactive Medications

Lopinavir-ritonavir combination is being used for the treatment of SARS-CoV-2 infection. A low dose of ritonavir is added to other protease inhibitors to take advantage of potent inhibition of cytochrome (CYP) P450 3A4, thereby significantly increasing the plasma concentration of coadministered lopinavir. Ritonavir also inhibits CYP2D6 and induces CYP2B6, CYP2C19, CYP2C9, and CYP1A2. This potent, time-dependent interference of major hepatic drug-metabolizing enzymes by ritonavir leads to several clinically important drug-drug interactions. A number of patients presenting with acute coronary syndrome and acute heart failure may have SARS-CoV-2 infection simultaneously. Lopinavir-ritonavir is added to their prescription of multiple cardiac medications leading to potential drug-drug interactions. Many cardiology, pulmonology, and intensivist physicians have never been exposed to clinical scenarios requiring co-prescription of cardiac and antiviral therapies. Therefore, it is essential to enumerate these drug-drug interactions, to avoid any serious drug toxicity, to consider alternate and safer drugs, and to ensure better patient care.

Flecainide How and When: A Practical Guide in Supraventricular Arrhythmias

Transcatheter ablation was increasingly and successfully used to treat symptomatic drug refractory patients affected by supraventricular arrhythmias. Antiarrhythmic drug treatment still plays a major role in patient management, alone or combined with non-pharmacological therapies. Flecainide is an IC antiarrhythmic drug approved in 1984 from the Food and Drug Administration for the suppression of sustained ventricular tachycardia and later for acute cardioversion of atrial fibrillation and for sinus rhythm maintenance. Currently, flecainide is mostly used for sinus rhythm maintenance in atrial fibrillation (AF) patients without structural cardiomyopathy although recent studies enrolling different patient populations have demonstrated a good effectiveness and safety profile. How should we interpret the results of the CAST after the latest evidence? Is it possible to expand the indications of flecainide, and therefore, its use? This review aims to highlight the main characteristics of flecainide, as well as its optimal clinical use, delineating drug indications and contraindications and appropriate monitoring, based on the most recent evidence.

Antiarrhythmic effects of ginsenoside Rg2 on calcium chloride-induced arrhythmias without oral toxicity

BACKGROUND

Malignant arrhythmias require drug therapy. However, most of the currently available antiarrhythmic drugs have significant side effects. Ginsenoside Rg2 exhibits excellent cardioprotective effects and appears to be a promising candidate for cardiovascular drug development. So far, the oral toxicity and antiarrhythmic effects of Rg2 have not been evaluated.

METHODS

Acute oral toxicity of Rg2 was assessed by the Limit Test method in mice. Subchronic oral toxicity was determined by repeated dose 28-day toxicity study in rats. Antiarrhythmic activities of Rg2 were evaluated in calcium chloride-induced arrhythmic rats. Antiarrhythmic mechanism of Rg2 was investigated in arrhythmic rats and H9c2 cardiomyocytes.

RESULTS

The results of toxicity studies indicated that Rg2 exhibited no single-dose (10 g/kg) acute oral toxicity. And 28-day repeated dose treatment with Rg2 (1.75, 3.5 and 5 g/kg/d) demonstrated minimal, if any, subchronic toxicity. Serum biochemical examination showed that total cholesterol in the high-dose cohort was dramatically decreased, whereas prothrombin time was increased at Day 28, suggesting that Rg2 might regulate lipid metabolism and have a potential anticoagulant effect. Moreover, pretreatment with Rg2 showed antiarrhythmic effects on the rat model of calcium chloride induced arrhythmia, in terms of the reduced duration time, mortality, and incidence of malignant arrhythmias. The antiarrhythmic mechanism of Rg2 might be the inhibition of calcium influx through L-type calcium channels by suppressing the phosphorylation of Ca2+/calmodulin-dependent protein kinase II.

CONCLUSION

Our findings support the development of Rg2 as a promising antiarrhythmic drug with fewer side effects for clinical use.

New-onset postoperative atrial fibrillation after heart surgery

BACKGROUND

New-onset postoperative atrial fibrillation (poAF) complicates approximately 20-60% of all cardiac surgical procedures and is associated with an increased periprocedural mortality and morbitity, prolonged hospital stay, increased costs, and worse long-term survival. Unfortunately multiple advances in surgery and perioperative care over the last two decades have not led to a reduction in the incidence of poAF or associated complications in the daily clinical practice.

METHODS

A narrative review of the available literature was performed.

RESULTS

An extensive review of the pathophysiology of poAF following cardiac surgery, clinical, and procedural risk-factors is provided, as well as prophylactic measures and treatment.

CONCLUSION

Multiple strategies to prevent and manage poAF following heart surgery already exist. Our hope is that this review will facilitate more rigorous testing of prevention strategies, implementation of prophylaxis regimens as well as optimal treatment of this common and serious complication.

Potential Drug-drug Interactions in Acute Ischemic Stroke Patients at the Neurological Intensive Care Unit

Background

Clinically relevant potential drug-drug interactions are considered preventable adverse drug reactions.

Objective

The aim of this study was to ascertain the frequency of potential drug-drug interactions in acute ischemic stroke patients and to explore factors associated with occurrence of potentially contraindicated drug-drug interactions.

Methods

This observational retrospective cohort and nested case-control study was carried out among patients treated for acute ischemic stroke at the Neurological Intensive Care Unit in the Clinical Centre Kragujevac, Serbia. The potentially drug-drug interactions for each day of hospitalization were identifi ed using Micromedex® soft ware. Based on the existence or absence of potentially contraindicated drug-drug interactions, the participants were divided into a group of cases (n=111) and the control group (n=444).

Results

A total of 696 patients were analysed. All patients had a minimum of one potential drug-drug interaction during hospitalization. The most common drugs involved in potential drug-drug interactions were aspirin (8.02%), diclofenac (7.49%) and warfarin (7.14%). The number of medications prescribed for simultaneous use during hospitalisation and the use of antipsychotics in therapy signifi cantly increased the likelihood of potentially contraindicated drug-drug interactions aft er adjustment by means of logistic regression for 1.2 and 3 times, respectively.

Conclusions

This study suggests that patients with acute ischemic stroke are frequently exposed to potential drug-drug interactions. It is essential to identify potentially drug-drug interactions in these patients as early as possible in order to prevent adverse drug reactions and ensure safe recovery. Besides, full attention should be paid when adding each new medication in therapy, particularly when a neurologist decides to prescribe antipsychotics, such as risperidone.

Onco-cardiology: Drug-drug interactions of antineoplastic and cardiovascular drugs

Cardiovascular diseases (CVD) and cancer are still the leading causes of death. There are many common etiologic factors, especially smoking and obesity. Therefore, it is not uncommon for CVD and cancer to coexist. Drug-drug interactions (DDIs) inevitably occur in this group of patients, where polypharmacy is increasing due to older age and multiple comorbidities. However, multidisciplinary studies, especially close collaboration of medical oncologists and cardiologists, who deals with the diagnosis and treatment of these diseases, awareness and preventive approaches to DDIs may reduce serious morbidity and mortality. In this review, information about the common treatments used in cardiology and oncology and possible DDIs are discussed.

Clinically Important Drug-Drug Interactions Between Antiarrhythmic Drugs and Anticoagulants

Until the last decade, vitamin K antagonists (VKAs) were the only agents available for oral anticoagulation. Although effective and accessible, their use was complicated by a narrow therapeutic window, the need for regular monitoring of the international normalized ratio, and an associated susceptibility to interactions with both food and numerous medications. Furthermore, the onset of action was delayed, often requiring bridging with intravenous agents. In more recent years, we have enjoyed the development of nonvitamin-K-dependent, direct oral anticoagulants (DOACs), which either directly inhibit the activity of factor IIa (eg, dabigatran) or factor Xa (eg, rivaroxaban, apixaban, edoxaban). These medications boast a more rapid onset of action, predictable pharmacokinetics, wider therapeutic window, and equal or superior safety profiles. Although these medications appear to have fewer drug–drug interactions than VKAs, their interactions remain of clinical importance, particularly in one of the largest populations requiring anticoagulation: patients with atrial fibrillation. These patients are rarely on single medications, with the majority of them requiring some form of rate or rhythm control due to their arrhythmia. Unfortunately, data on interactions between DOACs and antiarrhythmic medications, despite their common coadministration, remain limited. Here, we summarize the interactions between antiarrhythmics and VKAs and review existing knowledge regarding their interactions with DOACs.

Physiologically-Based Pharmacokinetic Modeling for Drug-Drug Interactions of Procainamide and N-Acetylprocainamide with Cimetidine, an Inhibitor of rOCT2 and rMATE1, in Rats

Previous observations demonstrated that cimetidine decreased the clearance of procainamide (PA) and/or N-acetylprocainamide (NAPA; the primary metabolite of PA) resulting in the increased systemic exposure and the decrease of urinary excretion. Despite an abundance of in vitro and in vivo data regarding pharmacokinetic interactions between PA/NAPA and cimetidine, however, a mechanistic approach to elucidate these interactions has not been reported yet. The primary objective of this study was to construct a physiological model that describes pharmacokinetic interactions between PA/NAPA and cimetidine, an inhibitor of rat organic cation transporter 2 (rOCT2) and rat multidrug and toxin extrusion proteins (rMATE1), by performing extensive in vivo and in vitro pharmacokinetic studies for PA and NAPA performed in the absence or presence of cimetidine in rats. When a single intravenous injection of PA HCl (10 mg/kg) was administered to rats, co-administration of cimetidine (100 mg/kg) significantly increased systemic exposure and decreased the systemic (CL) and renal (CL_R) clearance of PA, and reduced its tissue distribution. Similarly, cimetidine significantly decreased the CL_R of NAPA formed by the metabolism of PA and increased the AUC of NAPA. Considering that these drugs could share similar renal secretory pathways (e.g., via rOCT2 and rMATE1), a physiologically-based pharmacokinetic (PBPK) model incorporating semi-mechanistic kidney compartments was devised to predict drug-drug interactions (DDIs). Using our proposed PBPK model, DDIs between PA/NAPA and cimetidine were successfully predicted for the plasma concentrations and urinary excretion profiles of PA and NAPA observed in rats. Moreover, sensitivity analyses of the pharmacokinetics of PA and NAPA showed the inhibitory effects of cimetidine via rMATE1 were probably important for the renal elimination of PA and NAPA in rats. The proposed PBPK model may be useful for understanding the mechanisms of interactions between PA/NAPA and cimetidine in vivo.

Interactions of Mexiletine with Novel Antiepileptic Drugs in the Maximal Electroshock Test in Mice: An Isobolographic Analysis

The aim of the study was to evaluate precisely the type of interactions between mexiletine (an antiarrhythmic drug) and four new generation antiepileptic drugs: lamotrigine, oxcarbazepine, topiramate and pregabalin in the maximal electroshock test in mice (MES). The isobolographic analysis was used to assess the nature of interactions between the tested drugs. Total brain concentrations of antiepileptics were also measured to detect possible pharmacokinetic interactions. The results obtained indicated that the mixture of mexiletine and pregabalin at the fixed ratios of 1:1 and 3:1 led to supra-additive interaction in terms of seizure suppression, while the proportion of 1:3 occurred additive. Synergism was also demonstrated for the combination of mexiletine and topiramate in all three proportions. Combinations of mexiletine with lamotrigine and mexiletine with oxcarbazepine were found to be additive. Adverse-effect profiles of mexiletine, antiepileptics and drug combinations were evaluated in the chimney test (motor coordination) and step-through passive-avoidance task (long-term memory). Mexiletine and drug combinations did not impair long-term memory. Moreover, all combinations of mexiletine with lamotrigine, oxcarbazepine and topiramate had no significant effect on motor coordination. However, the results from the chimney test indicated that pregabalin, administered alone at its ED₅₀ dose from the MES-test, significantly impaired motor performance. Similar adverse effects were observed when mexiletine was co-administered with pregabalin at the fixed-dose ratio combinations of 1:1 and 1:3. However, reduction of pregabalin dose at the fixed ratio of 3:1 seems to prevent significant motor impairment. The results may indicate that mexiletine can be considered as an adjunctive drug in antiepileptic treatment, particularly in patients with concomitant cardiac arrhythmia.

Drug-drug interactions involving antidepressants: focus on desvenlafaxine

Psychiatric and physical conditions often coexist, and there is robust evidence that associates the frequency of depression with single and multiple physical conditions. More than half of patients with depression may have at least one chronic physical condition. Therefore, antidepressants are often used in cotherapy with other medications for the management of both psychiatric and chronic physical illnesses. The risk of drug-drug interactions (DDIs) is augmented by complex polypharmacy regimens and extended periods of treatment required, of which possible outcomes range from tolerability issues to lack of efficacy and serious adverse events. Optimal patient outcomes may be achieved through drug selection with minimal potential for DDIs. Desvenlafaxine is a serotonin-norepinephrine reuptake inhibitor approved for the treatment of adults with major depressive disorder. Pharmacokinetic studies of desvenlafaxine have shown a simple metabolic profile unique among antidepressants. This review examines the DDI profiles of antidepressants, particularly desvenlafaxine, in relation to drugs of different therapeutic areas. The summary and comparison of information available is meant to help clinicians in making informed decisions when using desvenlafaxine in patients with depression and comorbid chronic conditions.

Evaluation of drug-related problems in older polypharmacy primary care patients

AIMS AND OBJECTIVES

Targeting older patients with predictive factors for drug-related problems (DRPs) could make clinical medication reviews more cost-effective. The aim of this study was to identify the number, type, and potential predictive factors for DRPs in older polypharmacy patients.

METHODS

Community pharmacists performed clinical medication reviews and documented DRPs, types of interventions, and their implementation in older patients.

RESULTS

Three hundred eighty-eight medication reviews were analyzed, 964 DRPs (average 2.5 ± 1.9), and 1022 interventions (average 2.6 ± 2.0) were identified. The overall implementation rate of interventions was 70.1%, the highest was observed in interventions aiming to resolve the lack of therapy monitoring (86.8%). Patients with ≥12 medications had an increased risk of ≥5 DRPs (P < .001). Asthma was associated with lack of adherence (P = .002), lack of aspirin, statins, and proton pump inhibitors use with additional therapy needed (P = .002-.004). Predictive factors for drug interactions were antihypertensive medications and/or medications with narrow therapeutic index (P < .05). Lack of efficacy was associated with diabetes (P = .006). Nonsteroidal anti-inflammatory drugs were risk factors for inappropriate drug selection (P = .002). Lack of monitoring was associated with hypertension (P = .013), whereas benzodiazepines (P < .001) and aspirin (P = .021) were overused.

CONCLUSION

Patients with asthma, hypertension, and diabetes and lack of statin, antithrombotic agent, and/or proton pump inhibitor use were associated with higher risks for DRPs.

Non–Health Care Facility Cardiovascular Medication Errors in the United States

Background: Prior studies have not examined national trends and characteristics of unintentional non–health care facility (HCF) medication errors associated with cardiovascular drugs. Objective: To investigate non-HCF medication errors associated with cardiovascular drugs reported to poison control centers in the United States. Methods: A retrospective analysis of non-HCF medication errors associated with cardiovascular drugs from 2000 to 2012 was conducted using the National Poison Data System database. Results: There were 278 444 medication errors associated with cardiovascular drugs reported to US poison control centers during the study period, averaging 21 419 exposures annually. The overall rate of cardiovascular medication errors per 100 000 population increased 104.6% from 2000 to 2012 ( P < 0.001) and the highest rates were among older adults. Most cases (83.6%) did not require treatment at a HCF. Serious medical outcomes were reported in 4.0% of exposures. The cardiovascular drugs most commonly implicated in medication errors were β-blockers (28.2%), calcium antagonists (17.7%), and angiotensin-converting enzyme inhibitors (15.9%). Most of the 114 deaths were associated with cardiac glycosides (47.4%) or calcium antagonists (29.8%). Most medication errors involved taking or being given a medication twice (52.6%). Conclusions: This study describes characteristics and trends of non-HCF cardiovascular medication errors over a 13-year period in the United States. The number and rate of cardiovascular medication errors increased steadily from 2000 to 2012, with the highest error rates among older adults. Further research is needed to identify prevention strategies for these errors, with a particular focus on the older adult population.

Old and new oral anticoagulants: Food, herbal medicines and drug interactions

The most commonly prescribed oral anticoagulants worldwide are the vitamin K antagonists (VKAs) such as warfarin. Factors affecting the pharmacokinetics of VKAs are important because deviations from their narrow therapeutic window can result in bleedings due to over-anticoagulation or thrombosis because of under-anticoagulation. In addition to pharmacodynamic interactions (e.g., augmented bleeding risk for concomitant use of NSAIDs), interactions with drugs, foods, herbs, and over-the-counter medications may affect the risk/benefit ratio of VKAs. Direct oral anticoagulants (DOACs) including Factor Xa inhibitors (rivaroxaban, apixaban and edoxaban) and thrombin inhibitor (dabigatran) are poised to replace warfarin. Phase-3 studies and real-world evaluations have established that the safety profile of DOACs is superior to those of VKAs. However, some pharmacokinetic and pharmacodynamic interactions are expected. Herein we present a critical review of VKAs and DOACs with focus on their potential for interactions with drugs, foods, herbs and over-the-counter medications.

Oral Adverse Drug Reactions to Cardiovascular Drugs

A great many cardiovascular drugs (CVDs) have the potential to induce adverse reactions in the mouth. The prevalence of such reactions is not known, however, since many are asymptomatic and therefore are believed to go unreported. As more drugs are marketed and the population includes an increasing number of elderly, the number of drug prescriptions is also expected to increase. Accordingly, it can be predicted that the occurrence of adverse drug reactions (ADRs), including the oral ones (ODRs), will continue to increase. ODRs affect the oral mucous membrane, saliva production, and taste. The pathogenesis of these reactions, especially the mucosal ones, is largely unknown and appears to involve complex interactions among the drug in question, other medications, the patient’s underlying disease, genetics, and life-style factors. Along this line, there is a growing interest in the association between pharmacogenetic polymorphism and ADRs. Research focusing on polymorphism of the cytochrome P450 system (CYPs) has become increasingly important and has highlighted the intra- and inter-individual responses to drug exposure. This system has recently been suggested to be an underlying candidate regarding the pathogenesis of ADRs in the oral mucous membrane. This review focuses on those CVDs reported to induce ODRs. In addition, it will provide data on specific drugs or drug classes, and outline and discuss recent research on possible mechanisms linking ADRs to drug metabolism patterns. Abbreviations used will be as follows: ACEI, ACE inhibitor; ADR, adverse drug reaction; ANA, antinuclear antigen; ARB, angiotensin II receptor blocker; BAB, beta-adrenergic blocker; CCB, calcium-channel blocker; CDR, cutaneous drug reaction; CVD, cardiovascular drug; CYP, cytochrome P450 enzyme; EM, erythema multiforme; FDE, fixed drug eruption; I, inhibitor of CYP isoform activity; HMG-CoA, hydroxymethyl-glutaryl coenzyme A; NAT, N-acetyltransferase; ODR, oral drug reaction; RDM, reactive drug metabolite; S, substrate for CYP isoform; SJS, Stevens-Johnson syndrome; SLE, systemic lupus erythematosus; and TEN, toxic epidermal necrolysis.

Clinical Pearls in Using Antiarrhythmic Drugs in the Outpatient Setting

A role for oral antiarrhythmic drugs (AADs) remains in clinical practice for patients with atrial and ventricular arrhythmias in spite of advances in nonpharmacologic therapy. Pharmacists play a vital role in the appropriate use of AAD dosing, administration, adverse effects, interactions, and monitoring. Pharmacists who are involved in providing care to patients with cardiac arrhythmias must remain updated regarding the efficacy and safety of the most commonly used AADs. This review will address key issues for appropriate initiation and maintenance of commonly selected Vaughan-Williams Class Ic and III agents in the outpatient setting.

P450-Based Drug-Drug Interactions of Amiodarone and its Metabolites: Diversity of Inhibitory Mechanisms

In this study, IC50 shift and time-dependent inhibition (TDI) experiments were carried out to measure the ability of amiodarone (AMIO), and its circulating human metabolites, to reversibly and irreversibly inhibit CYP1A2, CYP2C9, CYP2D6, and CYP3A4 activities in human liver microsomes. The [I]u/Ki,u values were calculated and used to predict in vivo AMIO drug-drug interactions (DDIs) for pharmaceuticals metabolized by these four enzymes. Based on these values, the minor metabolite N,N-didesethylamiodarone (DDEA) is predicted to be the major cause of DDIs with xenobiotics primarily metabolized by CYP1A2, CYP2C9, or CYP3A4, while AMIO and its N-monodesethylamiodarone (MDEA) derivative are the most likely cause of interactions involving inhibition of CYP2D6 metabolism. AMIO drug interactions predicted from the reversible inhibition of the four P450 activities were found to be in good agreement with the magnitude of reported clinical DDIs with lidocaine, warfarin, metoprolol, and simvastatin. The TDI experiments showed DDEA to be a potent inactivator of CYP1A2 (KI = 0.46 μM, kinact = 0.030 minute(-1)), while MDEA was a moderate inactivator of both CYP2D6 (KI = 2.7 μM, kinact = 0.018 minute(-1)) and CYP3A4 (KI = 2.6 μM, kinact = 0.016 minute(-1)). For DDEA and MDEA, mechanism-based inactivation appears to occur through formation of a metabolic intermediate complex. Additional metabolic studies strongly suggest that CYP3A4 is the primary microsomal enzyme involved in the metabolism of AMIO to both MDEA and DDEA. In summary, these studies demonstrate both the diversity of inhibitory mechanisms with AMIO and the need to consider metabolites as the culprit in inhibitory P450-based DDIs.

A pharmacogenetics-based warfarin maintenance dosing algorithm from Northern Chinese patients

Inconsistent associations with warfarin dose were observed in genetic variants except VKORC1 haplotype and CYP2C9*3 in Chinese people, and few studies on warfarin dose algorithm was performed in a large Chinese Han population lived in Northern China. Of 787 consenting patients with heart-valve replacements who were receiving long-term warfarin maintenance therapy, 20 related Single nucleotide polymorphisms were genotyped. Only VKORC1 and CYP2C9 SNPs were observed to be significantly associated with warfarin dose. In the derivation cohort (n = 551), warfarin dose variability was influenced, in decreasing order, by VKORC1 rs7294 (27.3%), CYP2C9*3(7.0%), body surface area(4.2%), age(2.7%), target INR(1.4%), CYP4F2 rs2108622 (0.7%), amiodarone use(0.6%), diabetes mellitus(0.6%), and digoxin use(0.5%), which account for 45.1% of the warfarin dose variability. In the validation cohort (n = 236), the actual maintenance dose was significantly correlated with predicted dose (r = 0.609, P<0.001). Our algorithm could improve the personalized management of warfarin use in Northern Chinese patients.

Structure-activity relationships of benzbromarone metabolites and derivatives as EYA inhibitory anti-angiogenic agents

The tyrosine phosphatase activity of the phosphatase-transactivator protein Eyes Absent (EYA) is angiogenic through its roles in endothelial cell migration and tube formation. Benzbromarone, a known anti-gout agent, was previously identified as an inhibitor of EYA with anti-angiogenic properties. Here we show that the major metabolite of BBR, 6-hydroxy benzbromarone, is a significantly more potent inhibitor of cell migration, tubulogenesis and angiogenic sprouting. In contrast, other postulated metabolites of BBR such as 5-hydroxy benzbromaorne and 1’-hydroxy benzbromarone are less potent inhibitors of EYA tyrosine phosphatase activity as well as being less effective in cellular assays for endothelial cell migration and angiogenesis. Longer substituents at the 2 position of the benzofuran ring promoted EYA3 binding and inhibition, but were less effective in cellular assays, likely reflecting non-specific protein binding and a resulting reduction in free, bio-available inhibitor. The observed potency of 6-hydroxy benzbromarone is relevant in the context of the potential re-purposing of benzbromarone and its derivatives as anti-angiogenic agents. 6-hydroxy benzbromarone represents a metabolite with a longer half-life and greater pharmacological potency than the parent compound, suggesting that biotransformation of benzbromarone could contribute to its therapeutic activity.

A Pharmacokinetic Study of the Combined Administration of Amiodarone and Ximelagatran, an Oral Direct Thrombin Inhibitor

The oral direct thrombin inhibitor ximelagatran is being developed for the prevention and treatment of thromboembolism. This single-blind, randomized, placebo-controlled, parallel-group study investigated the potential for the interaction of ximelagatran (36 mg every 12 hours for 8 days, measured as its active form melagatran in blood) and amiodarone (single 600-mg oral dose on day 4) in healthy male subjects (n = 26). For amiodarone + ximelagatran versus amiodarone + placebo, geometric mean ratios (90% confidence intervals for amiodarone AUC(0-120) and C(max) were 0.87 (0.69-1.08) and 0.86 (0.66-1.11), respectively. For desethylamiodarone, the principal metabolite of amiodarone, the corresponding ratios were 1.00 (0.89-1.12) for AUC(0-120) and 0.92 (0.77-1.09) for C(max). The geometric mean ratios (90% confidence intervals) for ximelagatran + amiodarone versus ximelagatran were 1.21 (1.17-1.25) for melagatran AUC(0-12) and 1.23 (1.18-1.28) for melagatran C(max). These confidence intervals were within or only slightly outside the interval, suggesting no interaction (0.8-1.25 for the effect of amiodarone on melagatran and 0.7-1.43 for the effect of melagatran on amiodarone or desethylamiodarone). Amiodarone did not affect the concentration-effect relationship of melagatran on activated partial thromboplastin time. Ximelagatran was well tolerated when coadministered with a single dose of amiodarone. Evaluation of the safety of the combination is needed to confirm that the relatively small pharmacokinetic changes in this study are of no clinical significance.

Herb-drug interaction of Fucus vesiculosus extract and amiodarone in rats: a potential risk for reduced bioavailability of amiodarone in clinical practice

Fucus vesiculosus is a seaweed claimed to be useful for obesity management. Therefore, considering the relationship between obesity and cardiovascular diseases, this work aimed to assess the potential for an herb-drug interaction among a standardized F. vesiculosus extract (GMP certificate) and amiodarone (a narrow therapeutic index drug) in rats. In a first pharmacokinetic study, rats were simultaneously co-administered with a single-dose of F. vesiculosus (575 mg/kg, p.o.) and amiodarone (50 mg/kg, p.o.); in a second study, rats were pre-treated during 14 days with F. vesiculosus (575 mg/kg/day, p.o.) and received amiodarone (50 mg/kg, p.o.) on the 15th day. Rats of the control groups received the corresponding volume of vehicle. After analysis of the pharmacokinetic data it deserves to be highlighted the significant decrease in the peak plasma concentration of amiodarone (55.4%) as well as the reduction of systemic exposure to the parent drug (~30%) following the simultaneous co-administration of F. vesiculosus extract and amiodarone. This paper reports, for the first time, the herb-drug interaction between F. vesiculosus and amiodarone, which determined a considerable decrease on amiodarone bioavailability in rats. Therefore, the therapeutic efficacy of amiodarone may be compromised by the concurrent administration of herbal slimming medicines/dietary supplements containing F. vesiculosus.

Use of antiarrhythmic drugs in elderly patients

Human aging is a global issue with important implications for current and future incidence and prevalence of health conditions and disability. Cardiac arrhythmias, including atrial fibrillation, sudden cardiac death, and bradycardia requiring pacemaker placement, all increase exponentially after the age of 60. It is important to distinguish between the normal, physiological consequences of aging on cardiac electrophysiology and the abnormal, pathological alterations. The age-related cardiac changes include ventricular hypertrophy, senile amyloidosis, cardiac valvular degenerative changes and annular calcification, fibrous infiltration of the conduction system, and loss of natural pacemaker cells and these changes could have a profound effect on the development of arrhythmias. The age-related cardiac electrophysiological changes include up- and down-regulation of specific ion channel expression and intracellular Ca(2+) overload which promote the development of cardiac arrhythmias. As ion channels are the substrates of antiarrhythmic drugs, it follows that the pharmacokinetics and pharmacodynamics of these drugs will also change with age. Aging alters the absorption, distribution, metabolism, and elimination of antiarrhythmic drugs, so liver and kidney function must be monitored to avoid potential adverse drug effects, and antiarrhythmic dosing may need to be adjusted for age. Elderly patients are also more susceptible to the side effects of many antiarrhythmics, including bradycardia, orthostatic hypotension, urinary retention, and falls. Moreover, the choice of antiarrhythmic drugs in the elderly patient is frequently complicated by the presence of co-morbid conditions and by polypharmacy, and the astute physician must pay careful attention to potential drug-drug interactions. Finally, it is important to remember that the use of antiarrhythmic drugs in elderly patients must be individualized and tailored to each patient's physiology, disease processes, and medication regimen.

Safety of flecainide

Flecainide is a class Ic antiarrhythmic agent that has an important role as part of rhythm control strategies in patients with atrial fibrillation (AF). Early clinical data on the use of flecainide showed an increase in arrhythmias and mortality compared with placebo in patients with a previous myocardial infarction and asymptomatic or mildly symptomatic ventricular arrhythmias. These findings only apply to a specific group of patients with left ventricular dysfunction and ischaemic heart disease, but had a negative impact on the use of class Ic antiarrhythmics across all indications and patient groups. The aim of this review was to evaluate the available safety data for flecainide in the literature and to assess its current use in patients with AF. Current European guidelines now recommend the use of flecainide in carefully selected groups of patients with AF who do not have structural heart disease. This includes for the cardioversion of recent-onset AF, pretreatment prior to direct current cardioversion, out-of-hospital acute oral therapy ('pill-in-the-pocket' approach) and for the ongoing maintenance of sinus rhythm. Potential cardiac adverse effects of flecainide include proarrhythmia, conduction abnormalities and negative inotropic effects. Dizziness is the most frequent non-cardiac side effect, followed by blurred vision and difficulty focusing; these are almost all mild, transient and tolerable. Data from recent clinical trials in patients with supraventricular arrhythmias suggest that flecainide has a good tolerability profile in groups of appropriately selected patients. Caution is required when using flecainide in patients with renal dysfunction, and there are a number of drug interactions, but these are well documented and manageable. Overall, flecainide is a good choice for the pharmacological management of AF. It has a good safety record and low incidence of adverse effects, rare end-organ toxicity and a low risk of ventricular proarrhythmia. To ensure that the benefits of treatment outweigh any potential risks, careful patient selection and monitoring is required.

Warfarin-amiodarone drug-drug interactions: determination of [I](u)/K(I,u) for amiodarone and its plasma metabolites

A retrospective clinical evaluation in a cohort of 73 patients receiving stable anticoagulation therapy showed that the addition/elimination of amiodarone resulted in a 6–65% change in warfarin dose requirement. To evaluate the roles of amiodarone and its circulating metabolites in this highly variable inhibitory drug interaction, an LC-ESI⁺ MS/MS assay was developed for the quantitation of low concentrations of these compounds in human plasma, utilizing newly synthesized deuterated analogs as internal standards. K_I’s were determined for the inhibition of (S)-warfarin 7-hydroxylation in human liver microsomes, by parent drug and metabolites, and unbound drug fractions (f_u) were measured so that the ratio of unbound plasma concentration to the microsomal K_I for unbound drug ([I]_u/K_I,_u) could be calculated. From these ratios, we predict a minor metabolite, N,N-didesethylamiodarone, to be a major contributor to the drug interaction between warfarin and amiodarone.

TASK Channel Deletion Reduces Sensitivity to Local Anesthetic-induced Seizures

BACKGROUND

Local anesthetics (LAs) are typically used for regional anesthesia but can be given systemically to mitigate postoperative pain, supplement general anesthesia, or prevent cardiac arrhythmias. However, systemic application or inadvertent intravenous injection can be associated with substantial toxicity, including seizure induction. The molecular basis for this toxic action remains unclear.

METHODS

We characterized inhibition by different LAs of homomeric and heteromeric K channels containing TASK-1 (K2P3.1, KCNK3) and TASK-3 (K2P9.1, KCNK9) subunits in a mammalian expression system. In addition, we used TASK-1/TASK-3 knockout mice to test the possibility that TASK channels contribute to LA-evoked seizures.

RESULTS

LAs inhibited homomeric and heteromeric TASK channels in a range relevant for seizure induction; channels containing TASK-1 subunits were most sensitive and IC₅₀ values indicated a rank order potency of bupivacaine > ropivacaine >> lidocaine. LAs induced tonic-clonic seizures in mice with the same rank order potency, but higher LA doses were required to evoke seizures in TASK knockout mice. For bupivacaine, which produced the longest seizure times, seizure duration was significantly shorter in TASK knockout mice; bupivacaine-induced seizures were associated with an increase in electroencephalogram power at frequencies less than 5 Hz in both wild-type and TASK knockout mice.

CONCLUSIONS

These data suggest that increased neuronal excitability associated with TASK channel inhibition by LAs contributes to seizure induction. Because all LAs were capable of evoking seizures in TASK channel deleted mice, albeit at higher doses, the results imply that other molecular targets must also be involved in this toxic action.

Cytochrome P450-mediated cardiovascular drug interactions

INTRODUCTION

There are numerous drug-drug interactions (DDIs) related to cardiovascular medications and many of these are mediated via the cytochrome P450 (CYP) system. Some of these may lead to serious adverse events and it is, therefore, essential that clinicians are aware of the important interactions that occur.

AREAS COVERED

An extensive literature search was performed to analyze the CYP-mediated cardiovascular DDIs that lead to a loss of efficacy or potential toxicity. Cardiovascular drugs may be victims or act as perpetrators of DDIs. The paper analyzes CYP-mediated drug interactions concerning anticoagulants, antiplatelet agents, antiarrhythmics, β-blockers, calcium antagonists, antihypertensive medications, lipid-lowering drugs and oral antidiabetic agents.

EXPERT OPINION

Cardiovascular DDIs involving the CYP system are numerous. Additionally, the spectrum of drugs prescribed is constantly changing, particularly with cardiovascular diseases and it is not necessarily the case that drugs that had shown safety earlier will always show safety. Clinicians are encouraged to develop their knowledge of CYP-mediated DDIs so that they can choose safe drug combination regimens, adjust drug dosages appropriately and conduct therapeutic drug monitoring for drugs with narrow therapeutic indices.

Local anesthetic inhibits hyperpolarization-activated cationic currents

Systemic administration of local anesthetics has beneficial perioperative properties and an anesthetic-sparing and antiarrhythmic effect, although the detailed mechanisms of these actions remain unclear. In the present study, we investigated the effects of a local anesthetic, lidocaine, on hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels that contribute to the pacemaker currents in rhythmically oscillating cells of the heart and brain. Voltage-clamp recordings were used to examine the properties of cloned HCN subunit currents expressed in Xenopus laevis oocytes and human embryonic kidney (HEK) 293 cells under control condition and lidocaine administration. Lidocaine inhibited HCN1, HCN2, HCN1-HCN2, and HCN4 channel currents at 100 μM in both oocytes and/or HEK 293 cells; it caused a decrease in both tonic and maximal current (∼30-50% inhibition) and slowed current activation kinetics for all subunits. In addition, lidocaine evoked a hyperpolarizing shift in half-activation voltage (ΔV(1/2) of ∼-10 to -14 mV), but only for HCN1 and HCN1-HCN2 channels. By fitting concentration-response data to logistic functions, we estimated half-maximal (EC(50)) concentrations of lidocaine of ∼30 to 40 μM for the shift in V(1/2) observed with HCN1 and HCN1-HCN2; for inhibition of current amplitude, calculated EC(50) values were ∼50 to 70 μM for HCN1, HCN2, and HCN1-HCN2 channels. A lidocaine metabolite, monoethylglycinexylidide (100 μM), had similar inhibitory actions on HCN channels. These results indicate that lidocaine potently inhibits HCN channel subunits in dose-dependent manner over a concentration range relevant for systemic application. The ability of local anesthetics to modulate I(h) in central neurons may contribute to central nervous system depression, whereas effects on I(f) in cardiac pacemaker cells may contribute to the antiarrhythmic and/or cardiovascular toxic action.

Management of atrial fibrillation: translating clinical trial data into clinical practice

Atrial fibrillation is a supraventricular tachyarrhythmia with significant consequences in terms of morbidity and mortality. In light of the limitations of available pharmacologic treatment options (suboptimal efficacy plus safety and tolerability issues), atrial fibrillation management should be individualized based on patient characteristics and comorbidities that could influence response to specific management approaches. The importance of adequate anticoagulation should not be overlooked. This review provides a practical guide for primary care physicians, internists, and cardiologists on current management strategies for atrial fibrillation, based on recent guidelines and current clinical data.