[Every sixth patient in amiodarone treatment develops thyrotoxicosis or hypothyreosis]

Amiodarone is associated with multiple side effects among which a substantial number of patients are suffering from amiodarone-induced thyroid disease. In this review we present difficulties in diagnosing, sub typing and treating amiodarone-induced thyroid disease and give views on the future of this drug and one of the alternatives, dronedarone. Amiodarone holds a place in modern medicine due to its unique antiarrhythmic effects and associated thyroid diseases requires collaboration between cardiologists and endocrinologists due to the complexity hereof.

[Appropriateness criteria for the treatment of atrial fibrillation with dronedarone: practical issues. An Italian cardiologists' expert opinion]

Antiarrhythmic agents are among the therapeutic options available for the treatment of atrial fibrillation when a rhythm control strategy is required. Although their efficacy seems to be generally comparable to that of nonpharmacological interventions, the use of these agents remains controversial. In particular, among this class of drugs, the use of dronedarone in clinical practice is a matter of debate. In this paper, the authors aimed to address these issues, involving a team of expert cardiologists who discussed about the potential use of dronedarone in different clinical scenarios. The RAND/UCLA appropriateness method was used to develop appropriateness measures for the optimal management of patients treated with dronedarone, by combining the best available scientific evidence with the collective judgment of experts. To this purpose, a group of experts was identified and asked to rate the benefit-to-harm ratio of 52 clinical scenarios. Each indication was classified as "appropriate", "uncertain" or "inappropriate" in accordance with the panelists' median score. The classification of each scenario has led to the development of several recommendations for clinical practice. The use of dronedarone for the management of paroxysmal and persistent atrial fibrillation has evolved over time: this antiarrhythmic drug appears to be useful not only in monitoring symptoms, but also in reducing hospitalization and mortality rates in patients with atrial fibrillation.

Dronaderone-induced phototoxicity

Phototoxicity is a skin reaction that occurs in patients using photosensitizing drugs in combination with exposure to ultraviolet light. Common photosensitizing pharmacologic agents include antibiotics, non-steroidal anti-inflammatory drugs, diuretics, neuroleptics, retinoids, and amiodarone. Dronaderone is a novel antiarrhythmic that is similar in composition to amiodarone, but is non-iodinated and also has a methane-sulfonyl group, significantly decreasing its incidence of adverse effects as compared to amiodarone. While phototoxicity is a commonly reported complication of amiodarone, this reaction has rarely been documented in patients using dronaderone. We report the case of a 63 year-old woman with a history of atrial fibrillation that presented with a phototoxic drug eruption following use of dronaderone for maintenance of normal sinus rhythm.

Amiodarone inhibits apamin-sensitive potassium currents

BACKGROUND

Apamin sensitive potassium current (I KAS), carried by the type 2 small conductance Ca(2+)-activated potassium (SK2) channels, plays an important role in post-shock action potential duration (APD) shortening and recurrent spontaneous ventricular fibrillation (VF) in failing ventricles.

OBJECTIVE

To test the hypothesis that amiodarone inhibits I KAS in human embryonic kidney 293 (HEK-293) cells.

METHODS

We used the patch-clamp technique to study I KAS in HEK-293 cells transiently expressing human SK2 before and after amiodarone administration.

RESULTS

Amiodarone inhibited IKAS in a dose-dependent manner (IC50, 2.67 ± 0.25 µM with 1 µM intrapipette Ca(2+)). Maximal inhibition was observed with 50 µM amiodarone which inhibited 85.6 ± 3.1% of IKAS induced with 1 µM intrapipette Ca(2+) (n = 3). IKAS inhibition by amiodarone was not voltage-dependent, but was Ca(2+)-dependent: 30 µM amiodarone inhibited 81.5±1.9% of I KAS induced with 1 µM Ca(2+) (n = 4), and 16.4±4.9% with 250 nM Ca(2+) (n = 5). Desethylamiodarone, a major metabolite of amiodarone, also exerts voltage-independent but Ca(2+) dependent inhibition of I KAS.

CONCLUSION

Both amiodarone and desethylamiodarone inhibit I KAS at therapeutic concentrations. The inhibition is independent of time and voltage, but is dependent on the intracellular Ca(2+) concentration. SK2 current inhibition may in part underlie amiodarone's effects in preventing electrical storm in failing ventricles.

Cost-effectiveness analysis of dronedarone versus other anti-arrhythmic drugs for the treatment of atrial fibrillation--results for Canada, Italy, Sweden and Switzerland

The ATHENA clinical trial enrolled 4,628 patients in 37 countries and evaluated the efficacy of dronedarone 400 mg twice daily versus placebo for the prevention of cardiovascular hospitalisation or death from any cause in patients with paroxysmal or persistent atrial fibrillation or atrial flutter. The trial showed a statistically significant 24% reduction in the primary endpoint cardiovascular hospitalisations or all-cause death. In the current paper, parameters that drive the cost-effectiveness of dronedarone on top of standard therapy versus likely comparators, i.e. amiodarone, sotalol and flecainide, were investigated by means of a health economic model based on the ATHENA clinical trial. Dronedarone is cost-effective, and ICERs are low versus amiodarone with €5,340; €4,620; €3,850 and €5,630 per QALY gained for Canada, Italy, Sweden and Switzerland, respectively. The most significant driving factor for the cost-effectiveness of dronedarone is the increased survival rate for patients on dronedarone.

Usefulness of dronedarone in patients with atrial arrhythmias

Dronedarone is a novel class III antiarrhythmic drug with moderate efficacy in preventing atrial arrhythmias. However, only few data from the real-world use of dronedarone with limited electrocardiographic monitoring are available. The investigators report the incidence, timing, and reasons for discontinuation of dronedarone; maintenance of sinus rhythm; and atrial arrhythmia recurrence patterns in 120 consecutive patients with atrial fibrillation (AF; n = 91) or non-isthmus-dependent atrial flutter (n = 29) treated with dronedarone (400 mg twice daily). Rhythm control was assessed with serial 7-day Holter electrocardiography after 4 weeks and after 6 to 9 months. After drug initiation, dronedarone was discontinued in 19 patients (16%) because of inefficacy (n = 7 [6%]) or adverse events (n = 12 [10%]). At 4 weeks, 44 patients (37%) had stopped taking dronedarone because of inefficacy (n = 27 [23%]) or adverse events (n = 17 [14%]). After 6 to 9 months, 25 patients (21%) had discontinued dronedarone because of clinical inefficacy (n = 16 [13%]) or adverse events (n = 9 [8%]). Overall, dronedarone was still used after 6 to 9 months in 32 patients (27%). Maintenance of sinus rhythm was achieved in 40 patients (33%) after 4 weeks and in 24 patients (20%) after 6 to 9 months. Reversal from persistent to paroxysmal arrhythmias was observed in 23 patients, (29%) whereas progression from paroxysmal to persistent arrhythmias occurred in 6 patients (15%). Conversion from AF to non-isthmus-dependent atrial flutter was noted in 10 patients (13%). In conclusion, dronedarone is associated with frequent adverse events and moderate antiarrhythmic efficacy requiring discontinuation in most patients within the first 9 months of use, and there is a prevalent reversal from persistent to paroxysmal but also from paroxysmal to persistent atrial arrhythmias and from AF to non-isthmus-dependent atrial flutter.

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.

Effects of dronedarone started rapidly after amiodarone discontinuation

BACKGROUND

Multiple studies have shown that amiodarone is effective in treating atrial fibrillation (AF), but is associated with a relatively high incidence of side effects; however, due to amiodarone's long elimination half-life (20-100 days), physicians may hesitate to start other drugs until it has fully cleared.

HYPOTHESIS

A rapid switch from amiodarone to dronedarone is feasible.

METHODS

EURIDIS and ADONIS were double-blind, multinational, parallel-group trials comparing the efficacy and safety of dronedarone with placebo over 12 months. This retrospective subanalysis of EURIDIS/ADONIS compared the effects of dronedarone in patients discontinuing amiodarone within 2 days before randomization ("rapid switch") with results in patients who had received no amiodarone during the 2 months preceding randomization.

RESULTS

In total, 1237 patients were enrolled ("rapid switch", n = 154; "no amiodarone", n = 1014). In both the "rapid switch" and the "no amiodarone" groups, dronedarone users had significantly lower AF recurrence than patients receiving placebo (HR = 0.64, 95% CI, 0.44-0.95; P = 0.0224 and HR = 0.79, 95% CI, 0.67-0.92; P = 0.0027, respectively). Dronedarone users had a higher incidence of bradyarrhythmic events than placebo-treated patients. A "rapid switch" from amiodarone to dronedarone was associated with a higher incidence of serious heart failure events and heart failure hospitalizations versus all other groups. Overall event rates were low and there was no significant difference in total adverse event rates or deaths between groups.

CONCLUSION

In this patient population, a switch from amiodarone to dronedarone within a 2-day time frame might be feasible in certain patient categories, but further investigation is warranted.

Ventricular tachycardia in "end stage" hypertrophic cardiomyopathy: a role of dronedarone

Hypertrophic cardiomyopathy (HCM) occurs in 1 in every 500 individuals. It represents the most common cause of sudden cardiac death in those under the age of twenty-five. 3-5% patients with HCM go on to develop the dilated, hypokinetic end stage (ES) HCM with systolic failure. They have a higher incidence of heart failure, sudden deaths and defibrillator shocks. To the best of our knowledge this is first report of successful use of dronedarone for suppression of VT associated with ES HCM.

[New antiarrhythmic drugs for the treatment of atrial fibrillation]

Atrial fibrillation (AF) is the most common arrhythmia encountered in clinical practice and a difficult-to-treat arrhythmia. Conventional antiarrhythmic drugs, including flecainide, propafenone, sotalol and amiodarone, have several limitations in terms of efficacy and tolerability, and have made new drug development crucial. In the last decade, intensive research was undertaken to find new pharmacological options for the treatment of AF, and two new drugs are now available. Vernakalant is an atrial-selective drug specifically designed to block sodium channels at the atrial level, and its intravenous formulation has recently been recommended for approval by the Food and Drug Administration for pharmacological conversion of AF. Dronedarone is a chemical derivative of amiodarone (though having a significantly different clinical profile) with effects on multiple ion channels that proved effective in reducing the rate of the combined endpoint of death from any cause and cardiovascular hospitalization in patients with non-permanent AF enrolled in the ATHENA study. The available evidence on the efficacy of dronedarone has led to approval for recommendation in many clinical situations in which rhythm control is desirable. The complexity of the mechanisms underlying AF and the large variability of associated comorbidities render the AF patient a unique entity, making the identification of patients who may benefit from these novel approaches challenging.

Efficacy and safety profile of dronedarone in clinical practice. Results of the Magdeburg Dronedarone Registry (MADRE study)

BACKGROUND

Dronedarone is a new antiarrhythmic agent that has only recently been approved for the therapy of atrial fibrillation (AF). Results regarding a broader spectrum of patients and experience accumulated in clinical practice are still very scarce. Therefore, we prospectively investigated the efficacy and tolerance of dronedarone in a real life setting.

METHODS AND RESULTS

The study included 191 patients (85 women) aged 63 ± 9.9 years with a history of paroxysmal or persistent AF. Follow-up time was 14.3 ± 4.9 months. In patients with persistent AF, sinus rhythm was restored using electrical cardioversion prior to dronedarone administration. Each patient underwent standard ECG on a daily basis during the first 4 days of treatment, and on days 7, 30 and 90, resp. After that, the patients had a follow-up visit every three months. Creatinine, creatine kinase, and hepatic enzymes were closely monitored. Clinical history was meticulously taken at multiple follow-up visits. Dronedarone maintained sinus rhythm in 33.5% (95% CI: 27%-40%), and AF recurrence rate was high: 66.5% (95% CI: 60%-73%). Adverse effects occurred in 31.9% (95% CI: 27%-38%) of the patients and necessitated permanent discontinuation of dronedarone in 22% (95% CI: 17%-27%).

CONCLUSIONS

The results suggest that dronedarone may not be superior to available antiarrhythmic agents and caution against its use as a first line therapy in AF.

Pharmacology of myocardial calcium-handling

Disturbed myocardial calcium (Ca(+)) handling is one of the pathophysiologic hallmarks of cardiovascular diseases such as congestive heart failure, cardiac hypertrophy, and certain types of tachyarrhythmias. Pharmacologic treatment of these diseases thus focuses on restoring myocardial Ca(2+) homeostasis by interacting with Ca(2+)-dependent signaling pathways. In this article, we review the currently used pharmacologic agents that are able to restore or maintain myocardial Ca(2+) homeostasis and their mechanism of action as well as emerging new substances.

Dronedarone prevents microcirculatory abnormalities in the left ventricle during atrial tachypacing in pigs

BACKGROUND AND PURPOSE

Atrial fibrillation induces ischaemic microcirculatory flow abnormalities in the ventricle, contributing to the risk for acute coronary syndromes. We evaluated the effect of dronedarone on ventricular perfusion during rapid atrial pacing (RAP).

EXPERIMENTAL APPROACH

Coronary and fractional flow reserve (CFR/FFR) were measured in the left anterior descending artery in 29 pigs. Six received RAP, six received RAP with dronedarone (RAP/D), seven received dronedarone alone, four received RAP with amiodarone (RAP/A), and six received neither (sham). In ventricular tissue, oxidative stress/ischaemia-related gene and protein expression was evaluated by RT-PCR and Western blotting; Isoprostanes were measured by GC-MS procedures.

KEY RESULTS

CFR was decreased in the RAP group, compared with other groups. FFR was not different between groups. Effective refractory period was reduced in RAP compared with RAP/D. RAP-activated PKC phosphorylation tended to be decreased by dronedarone (P= 0.055) RAP induced NOX-1 and NOX-2 protein and the mRNA for hypoxia-inducible factor-1α (HIF-1α). Dronedarone reduced the pacing-dependent increase in the expression of NOX-2 protein and of HIF-1α mRNA. The oxidative stress marker, F(2)-isoprostane, was increased by RAP and this increase was attenuated by dronedarone. Other oxidative stress/ischaemia-related genes were induced by RAP compared with sham and were decreased by dronedarone treatment. In HL1 cells, dronedarone significantly inhibited the increased phosphorylation of PKCα after oxidative stress, with an almost significant effect (P= 0.059) on that after RAP.

CONCLUSIONS AND IMPLICATIONS

Dronedarone abolished RAP-induced ventricular microcirculatory abnormalities by decreasing oxidative stress/ischaemia-related gene and protein expression in the ventricle.

Dronedarone for the treatment of atrial fibrillation: a NICE single technology appraisal

The National Institute for Health and Clinical Excellence (NICE) invited the manufacturer of dronedarone (Multaq®, Sanofi-Aventis Limited, UK) to submit evidence on the clinical and cost effectiveness of the anti-arrhythmic drug (AAD) for the treatment of atrial fibrillation (AF) and atrial flutter, as part of the Institute's single technology appraisal (STA) process. The Centre for Reviews and Dissemination and the Centre for Health Economics, both at the University of York, were commissioned to act as the independent Evidence Review Group (ERG). This article provides a description of the company submission, the ERG review and NICE's subsequent decisions regarding the use of dronedarone within the UK NHS. The ERG review comprised a critique of the submitted evidence on the clinical effectiveness and cost effectiveness of dronedarone. The ERG examined the search strategy used to obtain relevant evidence, the selection of studies included in the assessment, outcome measures chosen and statistical methods employed. The ERG also validated the manufacturer's decision analytic model and used it to explore the robustness of the cost-effectiveness results to key assumptions. The main clinical effectiveness evidence supporting the use of dronedarone as a treatment for AF came from four randomized controlled trials. These trials were compared with a broader set of trials examining the effectiveness of other AADs for AF: amiodarone, sotalol and class 1c agents (flecainide and propafenone). The evidence suggested that all AADs decreased the recurrence of AF but dronedarone had the smallest effect. A mixed treatment comparison analysis of the trials showed that dronedarone was associated with a lower risk of all-cause mortality than other AADs, but this was highly uncertain. There was limited evidence to assess the effect of dronedarone on stroke, and no statistically significant differences between dronedarone and other AADs were found for treatment discontinuation. From the evidence presented by the manufacturer, dronedarone appeared highly cost effective in each of the population groups examined compared with using standard baseline therapy alone as first-line treatment, or compared with sotalol or amiodarone as first-line AAD, with incremental cost-effectiveness ratios (ICERs) well below £20,000 per QALY gained. The ICER for dronedarone relative to class 1c agents was around £19,000 per QALY. Although the evidence presented by the manufacturer indicated that dronedarone was cost effective, the estimates of treatment effect relative to other AADs and safety in the longer term were highly uncertain. The NICE Appraisal Committee in its preliminary guidance did not recommend the use of dronedarone for AF. However, following the response from a large number of consultees and commentators, NICE revised its preliminary guidance to allow the use of the drug in a specific subgroup of AF patients with additional cardiovascular risk factors.

[Update on current care guidelines: atrial fibrillation]

According to the update of the Finnish guidelines for management of patients with atrial fibrillation (AF) dronedarone should be used only in patients with non-permanent AF as a second line medication. It is recommended to monitor the patients regularly and stop dronedarone if permanent AF, heart failure or other adverse events are detected. Dabigatran and rivaroxaban can be used as an alternative to warfarin in patients requiring oral anticoagulation therapy. The selection between warfarin and the new anticoagulants should be based on careful evaluation of the benefits and disadvantages of the drugs in a given patient.

[Amiodarone and thyroid dysfunction]

Amiodarone is a structural analogue of thyroid hormone, and some of its anti-arrhythmic actions and toxicity are attributable to its interaction with nuclear receptors of thyroid hormones. Being highly lipophilic, amiodarone is concentrated in many tissues and is eliminated, consequently, very slowly. It is preferably employed to manage life-threatening arrhythmias, including ventricular fibrillation and unstable ventricular tachycardia. Other indications include atrial fibrillation and flutter, severe congestive heart failure, prevention of atrial fibrillation recurrence, and even in emergency medical situations to prevent sudden cardiac death. The aim of this review is to provide an updated approach on amiodarone and its influence on thyroid physiology and to discuss and analyze in depth its potential and not infrequent thyroidal adverse effects such as hypothyroidism and thyrotoxicosis.