Effects of a new amiodarone-like agent, SR 33589, in comparison to amiodarone, D,L-sotalol, and lignocaine, on ischemia-induced ventricular arrhythmias in anesthetized pigs

Predictors of dronedarone plasma drug concentrations and effect on atrial fibrillation/atrial flutter recurrence: Analyses from the EURIDIS and ADONIS studies

BACKGROUND

In this post hoc analysis, we assessed patient characteristics as predictors of dronedarone trough concentrations and characterized the relationship of trough concentrations of dronedarone with its efficacy and safety.

HYPOTHESIS

Dronedarone is recommended as a 400 mg twice daily dose taken orally with meals. We hypothesize that drug concentration/bioavailability of dronedarone, measured as above- and below-median trough concentrations, does not impact the efficacy outcomes.

METHODS

Average trough concentrations (Ctrough_avg ) across multiple timepoints were calculated for each patient, and patient Ctrough_avg values were categorized as below-median or above-median concentrations. The effect of patient baseline characteristics on dronedarone Ctrough_avg was assessed in the below-median versus above-median groups. The effect of dronedarone in each Ctrough_avg group versus placebo on risk of first atrial fibrillation/atrial flutter (AF/AFL) recurrence and safety was also evaluated.

RESULTS

Overall, 1795 plasma samples were available from 507 dronedarone-treated patients. An above-median Ctrough_avg was associated with age ≥75 years, female sex, lower weight, higher pacemaker use, and higher oral anticoagulant use. The risk of adjudicated first AF/AFL recurrence was significantly lower with dronedarone versus placebo in the below-median (hazard ratio [HR]: 0.71; 95% confidence interval [CI]: 0.56-0.91; p = .0054) and above-median groups (HR: 0.63; 95% CI: 0.50-0.81; p = .0002). No difference in risk of AF/AFL recurrence was observed between the above- and below-median groups. Safety and tolerability of dronedarone were similar between groups.

CONCLUSION

Significant reduction in AF/AFL recurrence was observed in patients treated with dronedarone versus placebo, regardless of dronedarone concentrations above or below the median value.

Handling of Ventricular Fibrillation in the Emergency Setting

Ventricular fibrillation (VF) and sudden cardiac death (SCD) are predominantly caused by channelopathies and cardiomyopathies in youngsters and coronary heart disease in the elderly. Temporary factors, e.g., electrolyte imbalance, drug interactions, and substance abuses may play an additive role in arrhythmogenesis. Ectopic automaticity, triggered activity, and reentry mechanisms are known as important electrophysiological substrates for VF determining the antiarrhythmic therapies at the same time. Emergency need for electrical cardioversion is supported by the fact that every minute without defibrillation decreases survival rates by approximately 7%–10%. Thus, early defibrillation is an essential part of antiarrhythmic emergency management. Drug therapy has its relevance rather in the prevention of sudden cardiac death, where early recognition and treatment of the underlying disease has significant importance. Cardioprotective and antiarrhythmic effects of beta blockers in patients predisposed to sudden cardiac death were highlighted in numerous studies, hence nowadays these drugs are considered to be the cornerstones of the prevention and treatment of life-threatening ventricular arrhythmias. Nevertheless, other medical therapies have not been proven to be useful in the prevention of VF. Although amiodarone has shown positive results occasionally, this was not demonstrated to be consistent. Furthermore, the potential proarrhythmic effects of drugs may also limit their applicability. Based on these unfavorable observations we highlight the importance of arrhythmia prevention, where echocardiography, electrocardiography and laboratory testing play a significant role even in the emergency setting. In the following we provide a summary on the latest developments on cardiopulmonary resuscitation, and the evaluation and preventive treatment possibilities of patients with increased susceptibility to VF and SCD.

Dronedarone: An Amiodarone Analog for the Treatment of Atrial Fibrillation and Atrial Flutter

Objective:

To review the pharmacology, pharmacokinetics, clinical efficacy, and safety profile of dronedarone for the treatment of atrial fibrillation.

Data Sources:

A literature search was conducted using the search terms dronedarone, SR 33589, atrial fibrillation, and antiarrhythmic medication in MEDLINE (1966–February 2007), International Pharmaceutical Abstracts (1970–February 2007), and EMBASE (1990–February 2007). References from the identified trials and selected review articles were evaluated. Additional information, including abstracts and posters, was obtained from Sanofi-Aventis.

Study Selection and Data Extraction:

Published studies and meeting abstracts evaluating the effects of dronedarone in humans and animals were reviewed.

Data Synthesis:

Dronedarone is a novel antiarrhythmic medication to treat atrial fibrillation. Dronedarone has a multifaceted mechanism of action similar to that of amiodarone. Dronedarone works by blocking potassium, sodium, and calcium channels and exhibits antiadrenergic properties. The drug has been evaluated at doses of 400, 600, and 800 mg twice daily. It prolonged the time to atrial fibrillation recurrence to 60–158 days compared with 5–59 days with placebo and decreased heart rate during atrial fibrillation by 12–25 beats/min in clinical trials. Major adverse events include gastrointestinal side effects and risk of proarrhythmia. Dronedarone may increase the risk of mortality in patients with congestive heart failure.

Conclusions:

Dronedarone is a new antiarrhythmic agent for the treatment of atrial fibrillation. Further studies are needed to better define dronedarone's safety profile and place in therapy.

The use of dronedarone for recurrent ventricular tachycardia: a case report and review of the literature

Background

Dronedarone is a benzofuran derivative resembling amiodarone that was intended to reduce the iodine-associated tissue deposition and organ toxicity seen with the latter. The utility of dronedarone for patients with ventricular arrhythmias has not been thoroughly evaluated. We present our experience with its use to treat refractory ventricular tachycardia storm and review the literature.

Case presentation

An 85 year-old gentleman with multiple medical comorbidities including ischemic and non-ischemic cardiomyopathy with severe biventricular systolic dysfunction presented with ventricular tachycardia storm. Therapeutic options were limited given his frail medical status, failures of sotalol, mexilitine, and catheter ablation therapies along with drug-toxicities from amiodarone. Dronedarone was thus considered as off-label use following informed consent. The patient unfortunately developed fatal multisystem organ failure including acute severe hepatotoxicity from dronedarone.

Conclusion

Novel therapies for drug-refractory ventricular arrhythmias are long overdue given the limitations of available pharmacologic and non-pharmacologic options. Off-label use of antiarrhythmic agents such as dronedarone is considered a treatment of last-resort in patients who otherwise have no therapeutic options. Given the paucity of reported cases regarding dronedarone for the treatment of ventricular tachyarrhythmias, no conclusive recommendations can be made at this time aside from words of caution. Despite the potential ventricular antiarrhythmic effects of dronedarone, careful patient evaluation is required to identify those at greatest risk of drug-related adverse events particularly in those patients with significant comorbidities such as advanced hepatic, renal, and cardiovascular disease.

Dronedarone does not affect infarct volume as assessed by magnetic resonance imaging in a porcine model of myocardial infarction

Dronedarone has been demonstrated to be harmful in patients with recent decompensated heart failure. Furthermore, a PALLAS study reported that dronedarone therapy increases mortality rates in patients with permanent atrial fibrillation. Although a pathophysiological explanation for these finding remains to be elucidated, the long term effects of dronedarone on myocardial structure and stability have been suggested. The aim of the present study was to determine whether dronedarone therapy affects left ventricular (LV) function in a chronic model of myocardial infarction (MI). An anterior MI was induced in 16 pigs. Of these animals, eight pigs were then treated with dronedarone for 1 week prior to, and 4 weeks following MI, the remaining pigs served as controls. LV angiography was performed 4 weeks after MI to determine the LV ejection fraction (LVEF). A post‑mortem magnetic resonance imaging scan of the LV was then performed on the two groups (n=6) to determine the volume and size of the induced MI. Dronedarone therapy did not affect systemic and intracardiac hemodynamic parameters or LVEF during the follow‑up assessment. Of note, dronedarone had no negative effect on the total infarct volume and size and did not induce lethal proarrhythmic effects following the induced anterior MI. Therefore, the results suggested that dronedarone did not increase the volume or size of induced anterior MI and did not affect LV performance. Thus, dronedarone therapy was observed to be safe in a porcine model of anterior MI.

Benefit-risk assessment of dronedarone in the treatment of atrial fibrillation

Rhythm control in atrial fibrillation (AF) can be achieved using pharmacological therapy. Amiodarone is the most efficacious anti-arrhythmic agent; however, its use is limited due to an unfavourable safety profile, including pro-arrhythmia, thyroid, liver, skin and pulmonary complications. Dronedarone, which is structurally similar to amiodarone, was developed to try and achieve a favourable balance of efficacy and risk. Dronedarone has been evaluated in several large clinical trials, which have shown reduced mortality and hospitalization rates in patients with non-permanent AF. In patients with permanent AF and/or heart failure, dronedarone has been shown to cause increased mortality and morbidity and should not be used in these groups. Compared with amiodarone, dronedarone has fewer toxic effects (thyroid, skin, pulmonary) and, although less efficacious, may be used as first-line therapy for maintenance of sinus rhythm in patients with non-permanent AF. Clinicians must be vigilant in monitoring their patients to ensure they do not develop permanent AF or heart failure.

Dronedarone's inhibition of If current is the primary mechanism responsible for its bradycardic effect

INTRODUCTION

The mechanism(s) whereby dronedarone reduces sinus rate are not well understood, although L-type calcium channel antagonism, beta-adrenergic blockade, and inhibition of If are plausible.

METHODS AND RESULTS

In anesthetized pigs, we compared the effects of dronedarone to the prototypical If inhibitor, ivabradine, and the L-type calcium channel antagonist diltiazem on heart rate, mean arterial blood pressure (MAP), and contractility. Dronedarone's effects on the phenylephrine-induced rise in MAP and on the chronotropic response to isoproterenol were also investigated. Cumulative doses of dronedarone (0.5 mg/kg, i.v., and 5.0 mg/kg, i.v.; plasma level: 80 ± 16.1 nM) progressively reduced heart rate (P < 0.02) without changes in MAP or contractility as assessed by LV dP/dt (N = 6). Ivabradine (0.5 mg/kg, i.v.) similarly reduced heart rate (P < 0.01) without change in MAP (N = 6). Diltiazem (0.8 mg/kg, i.v.) reduced heart rate and MAP and decreased contractility (N = 6). Dronedarone blunted phenylephrine's alpha-receptor-mediated increase in MAP but did not alter the marked beta-adrenergic receptor (BAR)-mediated increase in heart rate induced by isoproterenol. When dronedarone injection was preceded by ivabradine, no further decrease in heart rate or change in MAP was observed (N = 6).

CONCLUSIONS

Dronedarone reduced heart rate without affecting MAP or contractility, effects that differ from L-type calcium channel blockade. Dronedarone did not antagonize BAR stimulation, and its heart-rate lowering effects were eliminated by prior administration of ivabradine. Thus, dronedarone's bradycardic action is likely due to inhibition of If and not to blockade of either L-type calcium channels or BAR.

Dronedarone for recurrent ventricular tachycardia: a real alternative?

Sustained ventricular tachycardia (VT) is an important cause of morbidity and sudden death in patients with dilated cardiomyopathy. Although ICD effectively terminate VT episodes and improve survival, shocks reduce quality of life, and episodes of VT predict increased risk of heart failure and death despite effective therapy. Patients suffering recurrent VT episodes remain a challenge. Antiarrhytmic therapy reduces VT episodes, but it is associated with serious adverse events, and disappointing efficacy. Catheter ablation has emerged as an important option to control recurrent VT, but major procedure-related complications, and even death, are still issues to concern. And even with these armamentaria, some patients still have recurrent VT episodes and ICD shocks. We report on a patient with non-ischemic dilated cardiomyopathy and recurrent ventricular tachycardia resistant to multiple antiarrhytmic agents, in whom dronedarone was effective in completely suppressing ventricular tachycardia episodes.

Dronedarone: an overview

Atrial fibrillation (AF) is the most common arrhythmia encountered in clinical practice. Until recently, a rhythm control strategy for AF has been limited by drug toxicity and side-effects, and landmark AF trials have shown that such a strategy is not superior to a rate control one. New antiarrhythmic drugs, free of undesired effects, would enhance the rhythm control strategy, with the possibility of sinus rhythm restoration and maintenance. One of the promising drugs recently approved for clinical use is dronedarone. This drug has amiodarone-like antiarrhythmic and electrophysiological properties, despite it having a modified structure and lacking an iodine moiety. Thus, dronedarone lacks amiodarone's organ toxicity (including adverse thyroid and pulmonary effects). The efficacy of dronedarone has been investigated in several clinical trials, proving its effect in the prevention of AF recurrence, rate control in paroxysmal/persistent and permanent AF, reduction of cardiovascular hospitalization or death from any cause, and others. Indirect comparisons with amiodarone, as well as one head-to-head study of the two drugs, indicate that the relative safety of dronedarone may be at a cost of its lower antiarrhythmic efficacy compared with amiodarone.

Dronedarone in high-risk permanent atrial fibrillation

BACKGROUND

Dronedarone restores sinus rhythm and reduces hospitalization or death in intermittent atrial fibrillation. It also lowers heart rate and blood pressure and has antiadrenergic and potential ventricular antiarrhythmic effects. We hypothesized that dronedarone would reduce major vascular events in high-risk permanent atrial fibrillation.

METHODS

We assigned patients who were at least 65 years of age with at least a 6-month history of permanent atrial fibrillation and risk factors for major vascular events to receive dronedarone or placebo. The first coprimary outcome was stroke, myocardial infarction, systemic embolism, or death from cardiovascular causes. The second coprimary outcome was unplanned hospitalization for a cardiovascular cause or death.

RESULTS

After the enrollment of 3236 patients, the study was stopped for safety reasons. The first coprimary outcome occurred in 43 patients receiving dronedarone and 19 receiving placebo (hazard ratio, 2.29; 95% confidence interval [CI], 1.34 to 3.94; P=0.002). There were 21 deaths from cardiovascular causes in the dronedarone group and 10 in the placebo group (hazard ratio, 2.11; 95% CI, 1.00 to 4.49; P=0.046), including death from arrhythmia in 13 patients and 4 patients, respectively (hazard ratio, 3.26; 95% CI, 1.06 to 10.00; P=0.03). Stroke occurred in 23 patients in the dronedarone group and 10 in the placebo group (hazard ratio, 2.32; 95% CI, 1.11 to 4.88; P=0.02). Hospitalization for heart failure occurred in 43 patients in the dronedarone group and 24 in the placebo group (hazard ratio, 1.81; 95% CI, 1.10 to 2.99; P=0.02).

CONCLUSIONS

Dronedarone increased rates of heart failure, stroke, and death from cardiovascular causes in patients with permanent atrial fibrillation who were at risk for major vascular events. Our data show that this drug should not be used in such patients. (Funded by Sanofi-Aventis; PALLAS ClinicalTrials.gov number, NCT01151137.).

Safety and efficacy of dronedarone in the treatment of atrial fibrillation/flutter

Dronedarone is an amiodarone analog but differs structurally from amiodarone in that the iodine moiety was removed and a methane-sulfonyl group was added. These modifications reduced thyroid and other end-organ adverse effects and makes dronedarone less lipophilic, shortening its half-life. Dronedarone has been shown to prevent atrial fibrillation/flutter (AF/AFl) recurrences in several multi-center trials. In addition to its rhythm control properties, dronedarone has rate control properties and slows the ventricular response during AF. Dronedarone is approved in Europe for rhythm and rate control indications. In patients with decompensated heart failure, dronedarone treatment increased mortality and cardiovascular hospitalizations. However, when dronedarone was used in elderly high risk AF/AFl patients excluding such high risk heart failure, cardiovascular hospitalizations were significantly reduced and the drug was approved in the USA for this indication in 2009 by the Food and Drug Administration. Updated guidelines suggest dronedarone as a front-line antiarrhythmic in many patients with AF/Fl but caution that the drug should not be used in patients with advanced heart failure. In addition, the recent results of the PALLAS trial suggest that dronedarone should not be used in the long-term treatment of patients with permanent AF.

Reduction of myocardial infarct size by dronedarone in pigs--a pleiotropic action?

Purpose

Dronedarone is a first-line drug to prevent the recurrence of atrial fibrillation according to ESC guidelines. In the recent ATHENA trial, dronedarone reduced mortality and also hospitalization for acute coronary syndrome in patients with atrial fibrillation. This beneficial effect suggests that dronedarone might have also an impact on events associated with ischemia/reperfusion injury.

Methods

Fourteen anesthetized pigs received either dronedarone (2.5 mg/kg) or placebo. Effects of dronedarone on heart rate and blood pressure were reversed by atrial pacing and aortic constriction before pigs were subjected to 90 min regional low-flow myocardial ischemia and 2 h reperfusion. Regional myocardial blood flow was measured with microspheres and infarct size determined by TTC staining.

Results

With comparable heart rate and left ventricular pressure during ischemia, dronedarone reduced infarct size from 34 ± 3% to 22 ± 4% (p < 0.05) of the area at risk. Subendocardial blood flow during ischemia was not different between groups. The relationship between ischemic subendocardial blood flow in the area at risk and infarct size was displaced downwards, reflecting a direct cardioprotective action of dronedarone.

Conclusion

The beneficial effect of dronedarone is attributed to cardioprotective properties, possibly through attenuation of calcium overload during myocardial ischemia/reperfusion.

Suppression of ventricular tachycardia with dronedarone: a case report

 

INTRODUCTION

Dronedarone is a multichannel blocker with similar electrophysiological properties to amiodarone. Dronedarone has not been studied in humans as an agent to suppress ventricular arrhythmias.

METHODS

This case report describes the dramatic antiarrhythmic effects of dronedarone in a patient with nonischemic cardiomyopathy and recurrent ventricular tachycardia, which was resistant to multiple antiarrhythmic agents and endocardial catheter ablation.

RESULTS

Dronedarone was effective in completely suppressing ventricular tachycardia.

CONCLUSION

Further research is needed to establish a potential larger role for dronedarone in controlling ventricular arrhythmias in humans.

Dronedarone: evidence supporting its therapeutic use in the treatment of atrial fibrillation

Introduction:

Dronedarone, a benzofuran derivative with a structure similar to amiodarone, has been developed as a potential therapy for patients with atrial fibrillation.

Aim:

To review the published evidence regarding the efficacy and safety of dronedarone use in patients with atrial fibrillation.

Evidence review:

Available evidence suggests that dronedarone 400 mg orally twice daily can lengthen the time to and decrease the overall recurrence of atrial fibrillation compared with placebo. Dronedarone may reduce risk of mortality and cardiovascular hospitalization. Patients with atrial fibrillation receiving dronedarone had improved ventricular rate control compared with patients receiving placebo. Dronedarone is associated with few serious adverse events except, notably, in patients with decompensated heart failure.

Place in therapy:

Dronedarone may have a role in rate and rhythm control for patients with atrial fibrillation. Dronedarone can reduce unique, but potentially serious, end points in patients with atrial fibrillation. Despite this, the exact role of dronedarone in the management of patients with atrial fibrillation continues to emerge. It remains uncertain if dronedarone should be considered a primary treatment strategy for atrial fibrillation. Dronedarone should not be administered to patients with decompensated heart failure.

Conclusion:

Dronedarone is a unique drug that may serve a key role to treat patients with atrial fibrillation.

Chronic Suppression of Ventricular Tachyarrhythmias in Patients with ICDs

In this review, we examine the data evaluating the role of adjuvant therapy with antiarrthymic drugs (AADs) in chronic suppression of ventricular tachyarrhythmias in the patient with an ICD. It must be noted that all uses of AADs for this indication represent "off-label" prescription. No AAD is approved by the Food and Drug Administration (FDA) specifically as a therapy to reduce ICD shocks.

Dronedarone

Oral dronedarone is a non-iodinated benzofurane derivative structurally related to amiodarone. Although it is considered a class III antiarrhythmic agent like amiodarone, it demonstrates multi-class electrophysiological activity. Data from the ATHENA study demonstrated that patients receiving oral dronedarone 400 mg twice daily for 12-30 months had a significantly lower risk of experiencing first hospitalization due to a cardiovascular event or death from any cause than those receiving placebo. Dronedarone exhibited rate- and rhythm-controlling properties in patients with atrial fibrilation (AF) or atrial flutter, significantly reducing the risk of a first recurrence of AF versus placebo following 12 months' therapy in the ADONIS and EURIDIS studies. In the ERATO study, dronedarone was also significantly more effective than placebo in terms of ventricular rate control. Furthermore, the beneficial effects of oral dronedarone on ventricular rate control were maintained during exercise and sustained with continued therapy. Oral dronedarone was generally well tolerated in the treatment of adult patients with AF and/or atrial flutter in clinical studies. The incidence of diarrhoea, nausea, bradycardia, rash and QT-interval prolongation was significantly higher with oral dronedarone than placebo in the large ATHENA study; however, serious cardiac-related adverse events were observed in <1% of oral dronedarone recipients.

Dronedarone

Amiodarone is the most effective antiarrhythmic drug for maintaining sinus rhythm for patients with atrial fibrillation. Extra-cardiac side effects have been a limiting factor, especially during chronic use, and may offset its benefits. Dronedarone is a noniodinated benzofuran derivative of amiodarone that has been developed for the treatment of atrial fibrillation and atrial flutter. Similar to amiodarone, dronedarone is a potent blocker of multiple ion currents, including the rapidly activating delayed-rectifier potassium current, the slowly activating delayed-rectifier potassium current, the inward rectifier potassium current, the acetylcholine activated potassium current, peak sodium current, and L-type calcium current, and exhibits antiadrenergic effects. It has been studied for maintenance of sinus rhythm and control of ventricular response during episodes of atrial fibrillation. Dronedarone reduces mortality and morbidity in patients with high-risk atrial fibrillation, but may be unsafe in those with severe heart failure. This article will review evidence of safety and effectiveness of dronedarone in patients with atrial fibrillation.

Dronedarone for atrial fibrillation: a new therapeutic agent

Atrial fibrillation is the most common of the serious cardiac rhythm disturbances and is responsible for substantial morbidity and mortality. Amiodarone is currently one of the most widely used and most effective antiarrhythmic agents for atrial fibrillation. But during chronic usage amiodarone can cause some serious extra cardiac adverse effects, including effects on the thyroid. Dronedarone is a newer therapeutic agent with a structural resemblance to amiodarone, with two molecular changes, and with a better side effect profile. Dronedarone is a multichannel blocker and, like amiodarone, possesses both a rhythm and a rate control property in atrial fibrillation. The US Food and Drug Administration approved dronedarone for atrial fibrillation on July 2, 2009. In this review, we discuss the role of dronedarone in atrial fibrillation.

In vitro effects of acute amiodarone and dronedarone on epicardial, endocardial, and M cells of the canine ventricle

Amiodarone (AM) is an antiarrhythmic agent widely used in the treatment of ventricular and supraventricular arrhythmias. Dronedarone (DR) is a new compound with a pharmacological profile similar to that of AM, but iodine free. We previously demonstrated that chronic AM treatment reduces transmural dispersion of repolarization (TDR) in the canine heart. We used standard microelectrode technique to evaluate the effects of acute AM (100 microM) and DR (30 microM) on epicardial (EPI), endocardial (ENDO), and M region tissues obtained from the left ventricular wall of the canine heart. Amiodarone (100 microM, 120 min of exposure) produced little change in the action potential duration of ENDO and EPI tissues, but it shortened the action potential of M cells, especially at slow rates, leading to a decrease in TDR. Similar results were observed with DR. Acute AM (100 microM) and DR (30 microM) eliminated d-sotalol-induced early afterdepolarizations (EADs) and triggered activity in 3 of 3 and 2 of 6 M cell preparations, respectively. The reduction of TDR and the elimination of EAD-induced triggered activity differentiates AM and DR from other class III agents. These effects may explain the efficacy and low arrhythmogenicity of acute AM and suggest a potential safe use of DR as an antiarrhythmic agent.

Dronedarone for maintenance of sinus rhythm in atrial fibrillation or flutter

BACKGROUND

Amiodarone is effective in maintaining sinus rhythm in atrial fibrillation but is associated with potentially serious toxic effects. Dronedarone is a new antiarrhythmic agent pharmacologically related to amiodarone but developed to reduce the risk of side effects.

METHODS

In two identical multicenter, double-blind, randomized trials, one conducted in Europe (ClinicalTrials.gov number, NCT00259428 [ClinicalTrials.gov] ) and one conducted in the United States, Canada, Australia, South Africa, and Argentina (termed the non-European trial, NCT00259376 [ClinicalTrials.gov] ), we evaluated the efficacy of dronedarone, with 828 patients receiving 400 mg of the drug twice daily and 409 patients receiving placebo. Rhythm was monitored transtelephonically on days 2, 3, and 5; at 3, 5, 7, and 10 months; during recurrence of arrhythmia; and at nine scheduled visits during a 12-month period. The primary end point was the time to the first recurrence of atrial fibrillation or flutter.

RESULTS

In the European trial, the median times to the recurrence of arrhythmia were 41 days in the placebo group and 96 days in the dronedarone group (P=0.01). The corresponding durations in the non-European trial were 59 and 158 days (P=0.002). At the recurrence of arrhythmia in the European trial, the mean (+/-SD) ventricular rate was 117.5+/-29.1 beats per minute in the placebo group and 102.3+/-24.7 beats per minute in the dronedarone group (P<0.001); the corresponding rates in the non-European trial were 116.6+/-31.9 and 104.6+/-27.1 beats per minute (P<0.001). Rates of pulmonary toxic effects and of thyroid and liver dysfunction were not significantly increased in the dronedarone group.

CONCLUSIONS

Dronedarone was significantly more effective than placebo in maintaining sinus rhythm and in reducing the ventricular rate during recurrence of arrhythmia.

Comparative antiarrhythmic efficacy of amiodarone and dronedarone during acute myocardial infarction in rats

The effects of dronedarone, a non-iodinated derivative of amiodarone, on ventricular tachycardia and ventricular fibrillation post-myocardial infarction are not well established. Fifty-five Wistar rats were randomly allocated to a 2-week oral treatment with either vehicle (n=18), amiodarone (30 mg/kg, n=20), or dronedarone (30 mg/kg, n=17). After acute coronary artery ligation, a single-lead electrocardiogram was continuously recorded for 24 h and episodes of ventricular tachycardia/fibrillation as well as mortality rates were analysed. Monophasic action potential recordings were obtained from the left ventricular epicardium at baseline and 24 h post-myocardial infarction. Thyroid hormones and catecholamines were measured using radioimmunoassay. Thyroid function was similar in the 3 groups. Compared to controls, amiodarone and dronedarone equally decreased the number of ventricular tachycardia/fibrillation episodes by approximately 75%. Both agents prevented the increase in monophasic action potential duration and in beat-to-beat variation. Norepinephrine levels were lower only after amiodarone treatment. Despite the observed antiarrhythmic effect, total mortality did not differ between groups (38.8% in controls, 30.0% in the amiodarone group and 58.8% in the dronedarone group), because of excess bradyarrhythmic mortality in both drug groups that reached significance in the dronedarone group. Dronedarone and amiodarone display similar antiarrhythmic efficacy post-myocardial infarction, partly by preventing repolarization inhomogeneity. However, dronedarone increases bradyarrhythmic mortality possibly secondary to its negative inotropic effects.

Dronedarone

Dronedarone, a potassium channel antagonist, is chemically related to amio-darone. It is being developed by sanofi-aventis as a class III antiarrhythmic agent for the treatment of atrial fibrillation and atrial flutter in the US and Europe. Dronedarone has a favourable benefit/risk ratio, with the absence of any proarrhythmic effects. Sanofi merged with Synthélabo to form Sanofi-Synthélabo in 1999. In August 2004, Sanofi-Synthelabo merged with Aventis to form sanofi-aventis. The ATHENA trial is a multinational, randomised, double-blind trial evaluating the effects of dronedarone (400mg bid) compared with placebo, over a minimum 12-month follow-up period, in patients with atrial fibrillation or flutter. The trial is investigating the efficacy of dronedarone in preventing cardiovascular hospitalisations or death from any cause. Enrolment was extended to 4300 patients in order to attain the planned rate of adverse events; patient recruitment is ongoing.Previously, sanofi-aventis completed two pivotal phase III trials in atrial fibrillation. The trials, EURIDIS (EURopean trial In atrial fibrillation or flutter patients for the maintenance of Sinus rhythm) and ADONIS (American-Australasian trial with DronedarONe In atrial fibrillation or flutter patients for the maintenance of Sinus rhythm), involved 1237 patients who were in sinus rhythm at the time of randomisation. Results showed dronedarone to have anti-arrhythmic effects and a favourable benefit/risk ratio, with the absence of any proarrhythmic effect.Another trial, ERATO (Efficacy and safety of dronedARone for The cOntrol of ventricular rate), took place in 35 centres across nine European countries assessing dronedarone in 174 patients with permanent atrial fibrillation. Dronedarone was in phase II trials in Japan for the treatment of atrial fibrillation; however, no recent developments have been reported.

The Novel Antiarrhythmic Drug Dronedarone: Comparison with Amiodarone

Dronedarone is a noniodinated benzofuran derivative that has been developed to overcome the limiting iodine-associated adverse effects of the commonly used antiarrhythmic drug, amiodarone. It displays a wide cellular electrophysiological spectrum largely similar to amiodarone, inhibiting the potassium currents I(Kr), I(Ks), I(KI), I(KACh), and I(sus), as well as sodium currents and L-type calcium currents in isolated cardiomyocytes. In addition, dronedarone exhibits antiadrenergic properties. In vivo, dronedarone has been shown to be more effective than amiodarone in several arrhythmia models, particularly in preventing ischemia- and reperfusion-induced ventricular fibrillation and in reducing mortality. However, an increased incidence of torsades de pointes with dronedarone in dogs shows that possible proarrhythmic effects of dronedarone require further evaluation. The clinical trails DAFNE, EURIDIS, and ADONIS indicated safety, antiarrhythmic efficacy and low proarrhythmic potential of the drug in low-risk patients. In contrast, the increased incidence of death in the dronedarone group of the discontinued ANDROMEDA trial raises safety concerns for patients with congestive heart failure and moderate to severe left ventricular dysfunction. Dronedarone appears to be effective in preventing relapses of atrial fibrillation and atrial flutter. Torsades de pointes, the most severe adverse effect associated with amiodarone, has not yet been reported in humans with dronedarone. Unlike amiodarone, dronedarone had little effect on thyroid function and hormone levels in animal models and had no significant effects on human thyroid function in clinical trials. In conclusion, dronedarone could be a useful drug for prevention of atrial fibrillation and atrial flutter relapses in low-risk patients. However, further experimental studies and long-term clinical trials are required to provide additional evidence of efficacy and safety of dronedarone.

A review of the pharmacokinetics, electrophysiology and clinical efficacy of dronedarone

The results of major clinical trials and advances in pharmacologic and nonpharmacologic therapies are continuing to alter treatment approaches for both atrial and ventricular arrhythmias. Originally developed as an antianginal medication, amiodarone serves as the most effective antiarrhythmic drug in the treatment of both atrial and life-threatening ventricular arrhythmias. However, amiodarone has complex pharmacokinetics and is associated with serious extracardiac side effects, partially due to the presence of an iodine moiety. With a better understanding of the mechanisms of arrhythmias and antiarrhythmic drugs, new antiarrhythmic agents are currently under development with the hope that they will be more effective and safer than currently available drugs. One such drug that might potentially fulfill this hope is dronedarone. This amiodarone-like compound lacks the iodine moiety, and is similar in structure and electrophysiologic mechanisms of action to amiodarone, to date no evidence of liver, thyroid or pulmonary toxicity has been reported. Three clinical trials demonstrate efficacy in suppressing recurrences of atrial fibrillation and there is also evidence of a rate-slowing benefit during atrial fibrillation/flutter. However, the ANtiarrhythmic trial with DROnedarone in Moderate-to-severe congestive heart failure Evaluating morbidity Decrease (ANDROMEDA) study, performed in patients with left ventricular dysfunction, demonstrated excess noncardiac mortality in patients treated with dronedarone. Although effective in the treatment of atrial fibrillation, the future of this novel amiodarone-like drug remains uncertain until further clarification of the excess mortality in heart failure patients is better studied.

Involvement of nitric oxide in amiodarone- and dronedarone-induced coronary vasodilation in guinea pig heart

Amiodarone, a powerful antiarrhythmic compound, possesses coronary and peripheral vasodilator properties. The mechanisms responsible for these effects remain incompletely understood. In the present study, the coronary effects of amiodarone and dronedarone, a non-iodinated amiodarone-like compound, were investigated in isolated guinea pig hearts perfused at constant flow with high K+ solution (40 mM). Amiodarone (0.01-10 microM), dronedarone (0.01-1 microM) and verapamil (0.01-10 microM) induced concentration-dependent decreases in coronary perfusion pressure. Amiodarone- and dronedarone-mediated reductions in coronary perfusion pressure were not modified by a cyclooxygenase inhibitor, indomethacin (3 microM). L-Nitro-L-arginine (L-NOARG; 3-100 microM) caused a rightward shift of concentration-response curves to amiodarone and dronedarone in a dose-dependent way; L-arginine, a nitric oxide (NO) precursor, reversed this effect. Furthermore, when guinea pigs were treated with NG-nitro-L-arginine methyl ester (L-NAME; 20 mg/kg), amiodarone could not reduce coronary perfusion pressure. NO synthase inhibition did not affect the coronary perfusion pressure response to verapamil. 1H-[1,2,4]Oxadiazole (4,3-a) quinoxalin-1-one (ODQ), a specific inhibitor of the guanylyl cyclase, inhibited the effects of amiodarone but not those of verapamil. In the presence of L-NOARG and ODQ, and in hearts from animals treated with L-NAME, a decrease in coronary perfusion pressure was still observed at the highest concentration of dronedarone. These results show that, in guinea pig hearts, the coronary vasodilation induced by amiodarone highly depends on nitric oxide. Dronedarone differs from amiodarone by a remaining relaxant effect, refractory to inhibition of NO synthase pathway, probably due to its Ca+ antagonist properties.

Electrophysiologic characterization of dronedarone in guinea pig ventricular cells

The electrophysiological properties of dronedarone (SR33589), a noniodinated amiodarone-like agent, were studied on action potential (AP) and contraction of papillary muscle and on membrane ionic currents, Ca2+ transient, and shortening of ventricular cells of the guinea pig heart. In multicellular preparations, dronedarone (3, 10, and 30 microM) decreased maximum rate of rise of AP (dV/dt max) with a concentration- and frequency-dependent relationship; resting potential was not modified and AP amplitude was decreased only at 30 microM. The effects of dronedarone on AP durations (APDs) at different percentages of repolarization were not significantly changed, except for a slight decrease in APD30 and APD50 at the highest concentration. In isolated ventricular myocytes, dronedarone inhibited rapidly activating delayed-rectifier K+ current (I(Kr)) (median inhibitory concentration [IC50] </= 3 microM voltage-independent); slowly activating delayed-rectifier K+ current (I(Ks)) (IC50 approximately/= 10 microM voltage-dependent and time-, frequency-, or use-independent); and inward rectifier potassium current (I(K1)) (IC50 >/= 30 microM). Dronedarone blocked L-type Ca2+ current (I(Ca(L))) (IC50 = 0.18 +/- 0.018 microM at a stimulation frequency of 0.033 Hz) in a use- and frequency-dependent manner. Simultaneously to these electrophysiological effects, dronedarone reduced contraction amplitudes of papillary muscle and decreased Ca2+ transient and shortening of ventricular myocytes. The results show that dronedarone is a multichannel blocker because it decreases dV/dt max (I(Na)), I(Ca(L)), I(Kr), I(Ks), and I(K1). These effects are accompanied by a reduction in free intracellular calcium and contraction amplitudes. Dronedarone does not significantly change APD whatever the stimulation frequency. Our data demonstrate that the acute electrophysiological characteristics of dronedarone, despite absence of iodine in its molecular structure, are very similar to those of amiodarone in cardiac ventricle.

Limited antifibrillatory effectiveness of clinically relevant concentrations of class I antiarrhythmics in isolated perfused rat hearts

The Langendorff-perfused rat heart with regional ischemia is increasingly used for evaluating drugs for prevention of phase-1, ischemia-induced ventricular fibrillation (VF). Surprisingly, the effectiveness of Class I antiarrhythmics has not been characterized in this model. One lower and one higher concentration of quinidine (0.79 and 7.90 microM), lidocaine (3.88 and 12.93 microM), and flecainide (0.74 and 1.48 microM), representing the peak unbound plasma and total blood concentrations, respectively, at "therapeutic" dosage, were evaluated. The left main coronary artery was occluded for 30 min to elicit phase-1 VF, after which reperfusion-induced VF was examined. In hearts perfused with Krebs' solution containing 3 mM K(+), the higher concentrations of quinidine and lidocaine reduced the incidence of phase-1 VF from 92% to 0% and 17% respectively, (each p < 0.05). The lower drug concentrations were ineffective. Flecainide was equi-effective at low and high concentrations, with VF incidence reduced from 92% to 17% (p < 0.05). Neither low nor high concentrations of any of the drugs affected the incidence of reperfusion-induced VF. Using hearts perfused with Krebs' containing 5 mM K(+), sufficient to substantially reduce control phase-1 VF incidence, the experiment was repeated to test for possible proarrhythmic activity. None of the three drugs increased arrhythmia incidence. In this model, it was not possible to suppress ischemia-induced and reperfusion-induced VF with flecainide, lidocaine, or quinidine at concentrations equivalent to peak unbound plasma levels after clinical administration. This may explain the lack of clinical benefit with these drugs against sudden cardiac death. Because none of the drugs were proarrhythmic in ischemic hearts in which arrhythmia susceptibility had been lowered by high K(+), it would seem that clinical proarrhythmia seen with these drugs may not be related to exacerbation of phase-1, ischemia-induced VF.

Electrophysiological effects of dronedarone (SR 33589), a noniodinated amiodarone derivative in the canine heart: comparison with amiodarone

The electrophysiological effects of dronedarone, a new nonionidated analogue of amiodarone were studied after chronic and acute administration in dog Purkinje fibres, papillary muscle and isolated ventricular myocytes, and compared with those of amiodarone by applying conventional microelectrode and patch-clamp techniques. Chronic treatment with dronedarone (2x25 mg(-1) kg(-1) day p.o. for 4 weeks), unlike chronic administration of amiodarone (50 mg(-1) kg(-1) day p.o. for 4 weeks), did not lengthen significantly the QTc interval of the electrocardiogram or the action potential duration (APD) in papillary muscle. After chronic oral treatment with dronedarone a small, but significant use-dependent V(max) block was noticed, while after chronic amiodarone administration a strong use-dependent V(max) depression was observed. Acute superfusion of dronedarone (10 microM), similar to that of amiodarone (10 microM), moderately lengthened APD in papillary muscle (at 1 Hz from 239.6+/-5.3 to 248.6+/-5.3 ms, n=13, P<0.05), but shortened it in Purkinje fibres (at 1 Hz from 309.6+/-11.8 to 287.1+/-10.8 ms, n=7, P<0.05). Both dronedarone (10 microM) and amiodarone (10 microM) superfusion reduced the incidence of early and delayed afterdepolarizations evoked by 1 microM dofetilide and 0.2 microM strophantidine in Purkinje fibres. In patch-clamp experiments 10 microM dronedarone markedly reduced the L-type calcium current (76.5+/-0.7 %, n=6, P<0.05) and the rapid component of the delayed rectifier potassium current (97+/-1.2 %, n=5, P<0.05) in ventricular myocytes. It is concluded that after acute administration dronedarone exhibits effects on cardiac electrical activity similar to those of amiodarone, but it lacks the 'amiodarone like' chronic electrophysiological characteristics.

Inhibitory effects of dronedarone on muscarinic K+ current in guinea pig atrial cells

Dronedarone (SR33589), an amiodarone-like noniodinated antiarrhythmic agent, is undergoing clinical trials in atrial fibrillation. Because vagal activation plays a role in the pathophysiology of supraventricular arrhythmias, we have assessed the ability of dronedarone (0.01, 0.1, and 1 microM), compared with amiodarone (0.1, 1, and 10 microM) to inhibit the muscarinic acetylcholine receptor-operated K+ current (I(K(ACh))) in single cells isolated from guinea pig atria (patch-clamp technique). I(K(ACh)) was activated by extracellular application of carbachol (10 microM) or by intracellular loading with GTP-gamma-S (100 microM). Dronedarone and amiodarone reduced the carbachol-induced I(K(ACh)) with an IC50 (concentration required for 50% inhibition) slightly above 10 nM and 1 microM, respectively. Dronedarone also inhibited the GTP-gamma-S induced K+ current by 28% and 58% at 0.01 and 0.1 microM, respectively. These data suggest that dronedarone inhibits I(K(ACh)) by depressing the function of K(ACh) channel itself or associated GTP-binding proteins. Compared with amiodarone, dronedarone is approximately 100 times more potent on I(K(ACh)) and seems more selective in inhibiting I(K(ACh)) with respect to its antagonism of other inward and outward currents reported in the literature. This relative high potency of dronedarone to reduce I(K(ACh)) may be involved, at least in part, in the antiarrhythmic action of dronedarone against atrial fibrillation.