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Dronedarone administration prevents body weight gain and increases tolerance of the heart to ischemic stress: a possible involvement of thyroid hormone receptor alpha1.

Hypothyroid heart displays a phenotype of cardioprotection against ischemia and this study investigated whether administration of dronedarone, an amiodarone-like compound that has been shown to preferentially antagonize thyroid hormone binding to thyroid hormone receptor alpha1 (TRalpha1), results in a similar effect. Dronedarone was given in Wistar rats (90 mg/kg, once daily (od) for 2 weeks) (DRON), while untreated animals served as controls (CONT). Hypothyroidism (HYPO) was induced by propylthiouracil administration. Isolated rat hearts were perfused in Langendorff mode and subjected to 20 minutes of zero-flow global ischemia (I) followed by 45 minutes of reperfusion (R). 3,5,3' Triiodothyronine remained unchanged while body weight and food intake were reduced. alpha-Myosin heavy chain (alpha-MHC) decreased in DRON while beta-myosin heavy chain (beta-MHC) and sarcoplasmic reticulum Ca2+ adenosine triphosphatase (ATPase) expression (SERCA) was similar to CONT. In HYPO, alpha-MHC and SERCA were decreased while beta-MHC was increased. Myocardial glycogen content was increased in both DRON and HYPO. In DRON, resting heart rate and contractility were reduced and ischemic contracture was significantly suppressed while postischemic left ventricular end-diastolic pressure and lactate dehydrogenase release (IU/L min) after I/R were significantly decreased. In conclusion, dronedarone treatment results in cardioprotection by selectively mimicking hypothyroidism. This is accompanied by a reduction in body weight because of the suppression of food intake. TRs might prove novel pharmacologic targets for the treatment of cardiovascular illnesses.

Adaptation, Physiological↗

Effects of amiodarone and dronedarone on voltage-dependent sodium current in human cardiomyocytes.

UNLABELLED: Effect of Dronedarone on Cardiac Na Current. INTRODUCTION: Amiodarone (AM) is a highly effective antiarrhythmic agent used in the management of both atrial and ventricular arrhythmias. Its noniodinated analogue dronedarone (SR) may have fewer side effects than AM. In this study, we compared the effects of AM and SR on the sodium current I(Na) in human atrial myocytes. METHODS AND RESULTS: INa was studied with the whole-cell, patch clamp technique. Both AM and SR induced a dose-dependent inhibition of I(Na) recorded at -40 mV from a holding potential of -100 mV. AM inhibited I(Na) by 41%+/- 11% (n = 4) at 3 microM, and by 80%+/- 7% (n = 5) at 30 microM. SR produced more potent block, inhibiting INa significantly at only 0.3 microM (23%+/- 10%, n = 4) and completely (97%+/- 4%, n = 4) at 3 microM. Both AM and SR had only moderate effects on voltage-dependent properties of I(Na) (current-voltage relationship, availability for activation) and had no effect on the current decay kinetics. CONCLUSION: Both AM and SR inhibit I(Na) significantly in single human atrial cells, showing that the two drugs have Class I antiarrhythmic properties. The acute effects of SR are more potent than those of AM. The study supports the idea that the iodinated form of the molecule has no part in the acute effect of AM on Na+ channels.

Adult↗

Electrophysiological effects of dronedarone (SR33589), a noniodinated benzofuran derivative, in the rabbit heart : comparison with amiodarone.

BACKGROUND: To overcome the side effects of amiodarone (AM), its noniodinated analogue, dronedarone (SR), was synthesized. In this study, its electrophysiological effects were compared with those of AM in rabbit hearts. METHODS AND RESULTS: Five animal groups (n=7 each) for 3 weeks received daily oral treatment of 1 of these regimens: (1) control, vehicle only; (2) AM 50 mg/kg (AM50); (3) AM 100 mg/kg (AM100); (4) SR 50 mg/kg (SR50); and (5) SR 100 mg/kg (SR100). ECGs were recorded before drug and at 3 weeks of drug before euthanasia. Action potentials were recorded from isolated papillary muscle and sinoatrial node by microelectrode techniques. The short-term effects were studied in controls (n=5) at various concentrations of SR (0 to 10 micromol/L) in tissue bath. Action potential duration at 50% (APD(50)) and 90% (APD(90)) repolarization and upstroke dV/dt (V(max)) at various cycle lengths were compared by ANOVA with repeated measures. Compared with control, AM and SR increased RR, QT, and QTc intervals (P<0.0001 for all). Ventricular APD(50) and APD(90) were lengthened by 20% to 49% as a function of dose (P<0.005 to <0.0001) and cycle length (P<0.001). SR100 effects were greater than those of AM100 (P<0.002). V(max) was decreased by both AM100 (P<0.0001) and SR100 (P<0.01). Sinoatrial node automaticity was slowed in treated groups compared with that of the control group (P<0.0001 for all). CONCLUSIONS: The electrophysiological effects of dronedarone are similar to those of AM but more potent, despite deletion of iodine from its molecular structure, a finding of importance for the development of future class III antiarrhythmic compounds.

Amiodarone↗

High affinity HERG K(+) channel blockade by the antiarrhythmic agent dronedarone: resistance to mutations of the S6 residues Y652 and F656.

Pharmacological inhibition of human-ether-a-go-go-related gene (HERG) K(+) channels by structurally and therapeutically diverse drugs is associated with the 'acquired' form of long QT syndrome and with potentially lethal cardiac arrhythmias. Two aromatic amino-acid residues (Y652 and F656) on the inner (S6) helices are considered to be key constituents of a high affinity drug binding site within the HERG channel pore cavity. Using wild-type (WT) and mutant HERG channels expressed in mammalian cell lines, we have investigated HERG channel current (I(HERG)) blockade at 37+/-1 degrees C by dronedarone (DRONED), a non-iodinated analogue of the Class III antiarrhythmic agent amiodarone (AMIOD). Under our conditions WT I(HERG) tails, measured at -40 mV following activating pulses to +30 mV, were blocked with IC(50) values of approximately 59 and 70 nM for DRONED and AMIOD, respectively. I(HERG) inhibition by DRONED was contingent upon channel gating, with block developing rapidly on membrane depolarization, but with no preference for activated over inactivated channels. High external [K(+)] (94 mM) reduced the potency of I(HERG) inhibition by both DRONED and AMIOD. Strikingly, mutagenesis to alanine of the S6 residue F656 (F656A) failed to eliminate blockade by both DRONED and AMIOD, whilst Y652A had comparatively little effect on DRONED but some effect on AMIOD. These findings demonstrate that high affinity drug blockade of I(HERG) can occur without a strong dependence on the Y652 and F656 aromatic amino-acid residues.

Amino Acid Substitution↗

Evaluation of the acute electrophysiologic effects of intravenous dronedarone, an amiodarone-like agent, with special emphasis on ventricular repolarization and acquired torsade de pointes arrhythmias.

In the anesthetized dog with complete chronic AV block (CAVB), we evaluated and compared the acute electrophysiologic effects of dronedarone i.v. (Dron, 2 times 2.5 mg/kg/10 min) and amiodarone i.v. (Amio, 2 times 5 mg/kg/10 min). This canine model with a high sensitivity for acquired torsade de pointes (TdP) provides an ideal substrate to evaluate ventricular repolarization abnormalities. Six ECG leads and two endocardial monophasic action potential (MAP) recordings in the left and right ventricle (LV and RV) were simultaneously recorded to measure QT time, action-potential duration (APD), interventricular dispersion (deltaAPD = LV(APD) - RV(APD)), early afterdepolarizations (EADs), ectopic beats (EBs), and TdP. Measurements were made at the spontaneous idioventricular rhythm (IVR) and 1,000-ms steady-state pacing. To investigate its short-term, antiarrhythmic properties, Dron was given after almokalant (0.12 mg/kg)-induced TdP. Furthermore, in another set of experiments, oral Dron (20 mg/kg, b.i.d) was given for 3 weeks to conscious CAVB dogs. Dron, i.v., shortened ventricular repolarization (QT, 435 +/- 60 to 360 +/- 55; LV(APD) 395 +/- 75 to 335 +/- 60 ms; p < 0.05), whereas IVR and ventricular effective refractory period (VERP, 225 +/- 30 to 230 +/- 30 ms) remained similar. Therefore the VERP/QT ratio increased (0.55 +/- 0.04 to 0.61 +/- 0.03; p < 0.05). Similar results were obtained with Amio, i.v.. Almokalant-induced TdP was characterized by an increased repolarization duration, deltaAPD, and EADs. Dron, i.v., suppressed the EADs, EBs, and TdP by a reduction and homogenization of repolarization (LV(APD), 505 +/- 110 to 455 +/- 80 ms, and deltaAPD, 110 +/- 55 to 65 +/- 40 ms). Long-term oral Dron increased the PP interval, CL-IVR, and QT(c) time. In contrast to oral treatment, Dron i.v. shortens ventricular repolarization parameters, resulting in suppression of EAD-dependent acquired TdP. The increased VERP/QT ratio after Dron i.v. may indicate an important second antiarrhythmic property.

Action Potentials↗

Beneficial effects of amiodarone and dronedarone (SR 33589b), when applied during low-flow ischemia, on arrhythmia and functional parameters asssessed during reperfusion in isolated rat hearts.

The effects of short-term amiodarone and dronedarone treatments on action potential characteristics and arrhythmia (ventricular tachycardia ) induced by reperfusion after global low-flow ischemia were studied in rat hearts. The actions of amiodarone and SR on recovery of coronary flow and contractile function were also determined. Isolated hearts were stabilized for 40 min and were then submitted to 25-min global low-flow ischemia (constant coronary flow, 0.3 ml/min) followed by 30 min of reperfusion at constant pressure. Drugs were applied only during ischemia: consequently, action potential duration (APD) tended to widen. During reperfusion, APD tended to recover or shorten, and the more complete the recovery, the less the arrhythmia. Despite its ability to widen APD during ischemia, amiodarone facilitated APD recovery during reperfusion. Moreover, APD shortening and ventricular tachycardia suppression exhibit a bell-shaped concentration-response relation, implying that the drugs affect ventricular tachycardia by a class III-independent action. These results point to an anti-ischemic action supported by improvement in function and inhibition of reactive hyperemia.

Action Potentials↗

Drug evaluation: dronedarone, a novel non-iodinated anti-arrhythmic agent.

sanofi-aventis (formerly Sanofi-Synthelabo) is developing the oral class III anti-arrhythmic agent dronedarone (Multaq) for the potential treatment and prevention of atrial fibrillation. In June 2005, sanofi-aventis submitted EU and US filings for atrial fibrillation. In October 2002, phase I trials for arrhythmia were reported to be ongoing in Japan.

Amiodarone↗

Dronedarone (Sanofi-Synthélabo).

Sanofi-Synthelabo (formerly Sanofi) is developing the class III antiarrhythmic agent, dronedarone, for the potential treatment of atrial fibrillation and ventricular tachycardia [157842]. Phase III trials for the treatment of arrhythmia are planned for 2001 [399945]. By December 1998, phase IIb trials for the treatment of cardiac arrhythmia had been initiated [295681,320585], and the compound was shown to have the same efficacy as, and better tolerability than amiodarone [330073]. By 1997, the compound had entered phase IIa trials in Europe [219077,295681]. In November 1997, Sanofi expected to file for marketing in 2001/2 [270242]. ABN Amro predicted sales of FFR 50 million in 2001, rising to FFR 150 million in 2002 [317536]. Lehman Brothers predicted a 20% chance of the compound reaching market, with a launch anticipated in 2003 and potential peak sales of $200 million in 2011 [346267].

Journal Article↗

Chronic amiodarone evokes no torsade de pointes arrhythmias despite QT lengthening in an animal model of acquired long-QT syndrome.

BACKGROUND: Amiodarone is an effective antiarrhythmic drug rarely associated with torsade de pointes arrhythmias (TdP). The noniodinated compound dronedarone could resemble amiodarone and be devoid of the adverse effects. In the dog with chronic complete atrioventricular (AV) block (CAVB) and acquired long-QT syndrome, the electrophysiological and proarrhythmic properties of the drugs were compared after 4 weeks of oral treatment. METHODS AND RESULTS: Amiodarone (n=7, 40 mg. kg(-1). d(-1)) and dronedarone (n=8, 20 mg/kg BID) were started at 6 weeks of CAVB (baseline). Six dogs served as controls. Surface ECGs and endocardially placed monophasic action potential catheters in the left (LV) and right (RV) ventricles were recorded to assess QTc time, action potential duration (APD), interventricular dispersion (DeltaAPD=LV APD minus RV APD), early afterdepolarizations (EADs), ectopic beats, and TdP. Both amiodarone (+21%) and dronedarone (+31%) increased QTc time. Amiodarone showed no increase in DeltaAPD in 4 of 7 dogs, whereas dronedarone augmented DeltaAPD in 7 of 8 animals. After dronedarone, TdP occurred in 4 of 8 dogs with the highest DeltaAPD (105+/-20 ms). TdP was never seen with amiodarone, not even in the dogs that had DeltaAPD values comparable to those with dronedarone. Furthermore, a difference existed in EADs and ectopic activity incidence (dronedarone 3 of 8; amiodarone 0 of 7), which was also seen during an epinephrine challenge. CONCLUSIONS: In the CAVB dog model, both amiodarone and dronedarone prolong QT time (class III effect). The absence of TdP with amiodarone seems to be related to homogeneous APD lengthening in the majority of dogs and the lack of EADs and/or ventricular ectopic beats in all.

Action Potentials↗

Dronerarone acts as a selective inhibitor of 3,5,3'-triiodothyronine binding to thyroid hormone receptor-alpha1: in vitro and in vivo evidence.

Dronedarone (Dron), without iodine, was developed as an alternative to the iodine-containing antiarrhythmic drug amiodarone (AM). AM acts, via its major metabolite desethylamiodarone, in vitro and in vivo as a thyroid hormone receptor alpha(1) (TRalpha(1)) and TRbeta(1) antagonist. Here we investigate whether Dron and/or its metabolite debutyldronedarone inhibit T(3) binding to TRalpha(1) and TRbeta(1) in vitro and whether dronedarone behaves similarly to amiodarone in vivo. In vitro, Dron had a inhibitory effect of 14% on the binding of T(3) to TRalpha(1), but not on TRbeta(1). Desethylamiodarone inhibited T(3) binding to TRalpha(1) and TRbeta(1) equally. Debutyldronedarone inhibited T(3) binding to TRalpha(1) by 77%, but to TRbeta(1) by only 25%. In vivo, AM increased plasma TSH and rT(3), and decreased T(3). Dron decreased T(4) and T(3), rT(3) did not change, and TSH fell slightly. Plasma total cholesterol was increased by AM, but remained unchanged in Dron-treated animals. TRbeta(1)-dependent liver low density lipoprotein receptor protein and type 1 deiodinase activities decreased in AM-treated, but not in Dron-treated, animals. TRalpha(1)-mediated lengthening of the QTc interval was present in both AM- and Dron-treated animals. The in vitro and in vivo findings suggest that dronedarone via its metabolite debutyldronedarone acts as a TRalpha(1)-selective inhibitor.

Amiodarone↗

[New anti-arrhythmics--hope or disappointment?].

The new anti-arrhythmic agents studied in the last decade have mostly come from research orientated towards determining the compounds which block the electrical currents implicated in the process of repolarisation (class III action). To this must be added dronedarone, which is related to amiodarone and as such displays the 4 classes of anti-arrhythmic properties. Pure class III agents prolong the cardiac action potential and therefore the refractory period and QT interval. The conduction velocity is unaltered. These agents act best on re-entry arrhythmias. Dofetilide is a prototype. The class III action is linked to blockade of the Ikr current and can paradoxically lower it at increased heart rates. Dofelitide has not shown a harmful effect on the survival of high risk ischaemic patients. The conversion of atrial tachyarrhythmias into sinus rhythm can be obtained in one to two thirds of cases. As for the prevention of these arrhythmias, its success rate can exceed 60%. On the other hand, the occurrence of torsades de pointe is in the order of 3%, justifying the initiation of treatment under hospital conditions. Ibutilide acts by blocking the Ikr and INa-s currents. Used only intravenously, this agent is capable of converting back to sinus rhythm a third of atrial fibrillation episodes and two thirds of flutter. The risk of torsades de pointe is 3.5% so this treatment must also be commenced in the hospital setting. Azimilide blocks multiple Iks channels as well as Ikr, Ica and Ina. The electrophysiological effect is sustained at rapid heart rates. When evaluated in patients with paroxysmal atrial fibrillation, azimide prolonged the interval until recurrence, associated with an excellent tolerance (torsades de pointe in 0.55% of cases). In a survival study, azimide demonstrated a neutral effect in high risk subjects with diminished ejection fraction and sinusal variability. Unlike the previous agents, dronedarone is a benzofurane with a similar structure to amiodarone but without iodine. The 800 mg dose is associated with the best risk-benefit ratio. In patients with left ventricular dysfunction, the administration of this agent has been associated with excess mortality. Two recent studies on the prevention of atrial fibrillation have demonstrated that dronedarone is moderately effective with an excellent general tolerance.

Anti-Arrhythmia Agents↗

Effects of metabolites and analogs of amiodarone on alveolar macrophages: structure-activity relationship.

Amiodarone, an antiarrhythmic drug toxic toward the lung, is metabolized through sequential modifications of the diethylaminoethoxy group to mono-N-desethylamiodarone (MDEA), di-N-desethylamiodarone (DDEA), and amiodarone-EtOH (B2-O-EtOH), whose effects on lung cells are unclear. To clarify this, we exposed rabbit alveolar macrophages to analogs with different modifications of the diethylaminoethoxy group and then searched for biochemical signs of cell damage, formation of vacuoles and inclusion bodies, and interference with the degradation of surfactant protein A, used as a tracer of the endocytic pathway. The substances studied included MDEA, DDEA, and B2-O-EtOH, analogs with different modifications of the diethylaminoethoxy group, fragments of the amiodarone molecule, and the antiarrhythmic agents dronedarone (SR-33589) and KB-130015. We found the following: 1). MDEA, DDEA, and B2-O-EtOH rank in order of decreasing toxicity toward alveolar macrophages, indicating that dealkylation and deamination of the diethylaminoethoxy group represent important mechanisms of detoxification; 2). dronedarone has greater, and KB-130015 has smaller, toxicity than amiodarone toward alveolar macrophages; and 3). the benzofuran moiety, which is toxic to liver cells, is not directly toxic toward alveolar macrophages.

Amiodarone↗

The JT-area indicates dispersion of repolarization in dogs with atrioventricular block.

UNLABELLED: Heterogeneity in cardiac repolarization (Delta APD) is known to be arrhythmic. In the dog model of chronic complete AV-block and acquired long QT syndrome, an increase in Delta MAPD (defined as left ventricular monophasic action potential duration (MAPD) minus right ventricular MAPD) is often associated with changes in T-wave morphology. The purpose of this study was to correlate known changes in Delta MAPD with the planimetric total area of the T-wave on the surface ECG (integral of J-T, mVx ms). METHODS: The relationship between Delta MAPD and total area of the T-wave (i.e., JT-area) was assessed in four different protocols with different types of dispersion: (1) class III drugs followed by levcromakalim (n= 7), (2) LAD coronary artery occlusion and reperfusion (n = 6), (3) dronedarone i.v., an amiodarone like agent (n = 5) and (4) steady state pacing at cycle lengths of 1000 ms and 500 ms (n = 5). RESULTS: Class III drugs increased Delta MAPD (55 +/- 40 ms to 120 +/- 50 ms(#), P<0.05), which was correlated (r = 0.74, P < 0.001) with JT-area (50 +/- 40 mV. ms to 95 +/- 35 mV x ms(#)). Ischemia increased both Delta MAPD (30 +/- 25 ms to 90 +/- 40 ms(#)) and JT-area (60 +/- 55 mV x ms to 75 +/- 50 mV x ms(#)). Both levcromakalim and reperfusion reversed these conditions. Dronedarone had no effect on Delta MAPD or on JT-area while a faster frequency reduced both Delta MAPD and JT-area. CONCLUSION: Changes in dispersion of ventricular repolarization are reflected by alterations in JT-area. This non-invasive parameter may therefore be used to indicate changes in heterogeneity in ventricular repolarization.

Action Potentials↗

In vivo and in vitro antiarrhythmic effects of SSR149744C in animal models of atrial fibrillation and ventricular arrhythmias.

SSR149744C (2-butyl-3-{4-[3-(dibutylamino)propyl]benzoyl}-1-benzofuran-5-carboxylate isopropyl fumarate) is a new noniodinated benzofuran derivative structurally related to amiodarone and dronedarone that is currently undergoing clinical trials as an antiarrhythmic agent. As SSR149744C exhibits electrophysiological and hemodynamic properties of class I, II, III, and IV antiarrhythmic agents, the aim of this study was to evaluate its acute intravenous (IV) or oral (PO) antiarrhythmic activities in in vitro and in vivo animal models of atrial and ventricular arrhythmias. In vagally induced atrial fibrillation (AF) in anesthetized dogs, SSR149744C (3 and 10 mg/kg IV) terminated AF in all 7 dogs and prevented reinduction in 4 out of 7 dogs; effective refractory periods of right atrium were dose-dependently and frequency-independently lengthened. In low-K+ medium-induced AF models, SSR149744C (0.1 to 1 microM) prevented AF in isolated guinea pig hearts in a concentration-dependent manner. At the ventricular level, SSR149744C (0.1 to 10 mg/kg IV and 3 to 90 mg/kg PO) prevented reperfusion-induced arrhythmias in anesthetized rats with a dose-effect relationship, and, at doses of 30 to 90 mg/kg PO, it reduced early (0-24 hours) mortality following permanent left coronary artery ligature in conscious rats. The present results show that SSR149744C is an effective antiarrhythmic agent in atrial fibrillation and in ventricular arrhythmias. Like amiodarone and dronedarone, its efficiency in these animal models of arrhythmias is likely be related to its multifactorial mechanism of action.

Administration, Oral↗

Topics on the Na+/Ca2+ exchanger: pharmacological characterization of Na+/Ca2+ exchanger inhibitors.

Using the whole-cell voltage clamp, we examined acute effects of various agents on Na(+)/Ca(2+) exchange current (I(NCX)) in guinea-pig cardiac ventricular cells and transfected cells. Among the antiarrhythmic drugs, amiodarone, bepridil, dronedarone, cibenzoline, azimilide, and aprindine inhibited I(NCX) in a concentration-dependent manner. We also investigated the effects on NCX of 2,3-buanedione monoxim (BDM) and selective NCX inhibitors such as KB-R7943, SEA0400, and SN-6. The presence of trypsin in the pipette solution attenuated the inhibitory effects on NCX of amiodarone, bepridil, and BDM, suggesting that these drugs inhibit NCX from the cytosolic side. In contrast, the trypsin-insensitive NCX inhibitors were aprindine, azimilide, dronedarone, cibenzoline, KB-R7943, SEA0400, and SN-6. KB-R7943, SEA0400, and SN-6 suppressed the uni-directional outward I(NCX) more potently than the uni-directional inward I(NCX). The mechanism of this mode-dependency is unknown, but is suggested to be related to intracellular Na(+) concentration.

Animals↗