Effect of amiodarone (AMD) on the antioxidant enzymes, lipid peroxidation and mitochondrial metabolism

Comedication with interacting drugs predisposes amiodarone users in cardiac and surgical intensive care units to acute liver injury: A retrospective analysis

Risk factors and underlying mechanisms for liver injury associated with amiodarone remain elusive. This study aimed to investigate the drug-related covariates for acute liver injury by amiodarone-an intriguing compound of high lipophilicity, with a long half-life and notable efficacy.The medical, pharmacy, and laboratory records of new amiodarone users admitted to the cardiac or surgical intensive care units of a medical center were examined retrospectively. A Cox regression model with time-varying dose-related variables of amiodarone was utilized to estimate the hazard ratio (HR) of amiodarone-associated liver injury while adjusting for concomitant therapy and relevant covariates.Of the 131 eligible patients among 6,572 amiodarone users (46,402 prescriptions), 6 were identified as amiodarone-associated liver injury cases. In comparison to controls (n = 125), this liver injury cohort (n = 6) had significantly higher numbers of amiodarone-interacting (2.7 ± 2.0 vs 0.9 ± 0.9 drugs, P = .02) and hepatotoxic (3.8 ± 0.8 vs 2.5 ± 1.7 drugs, P = .03) comedications. The number of comedications with amiodarone-interacting potential (HR 2.07, 95% confidence interval [CI] 1.02-4.22, P = .04) and amiodarone cumulative doses standardized by body surface area (HR 6.82, 95% CI 1.72-27.04, P = .01) were independent risk factors for liver injury associated with amiodarone.Drug-related (amiodarone cumulative dose, interacting drugs) factors were significant predictors of amiodarone-associated acute liver injury. A prudent evaluation of each medication profile is warranted to attain precision medicine at the level of patient care, especially for those treated by medications with complex physicochemical and pharmacokinetic properties, such as amiodarone.

Mitochondrial oxidative stress and respiratory chain dysfunction account for liver toxicity during amiodarone but not dronedarone administration

The role played by oxidative stress in amiodarone-induced mitochondrial toxicity is debated. Dronedarone shows pharmacological properties similar to those of amiodarone but several differences in terms of toxicity. In this study, we analyzed the effects of the two drugs on liver mitochondrial function by administering an equivalent human dose to a rat model. Amiodarone increased mitochondrial H(2)O(2) synthesis, which in turn induced cardiolipin peroxidation. Moreover, amiodarone inhibited Complex I activity and uncoupled oxidative phosphorylation, leading to a reduction in the hepatic ATP content. We also observed a modification of membrane phospholipid composition after amiodarone administration. N-acetylcysteine completely prevented such effects. Although dronedarone shares with amiodarone the capacity to induce uncoupling of oxidative phosphorylation, it did not show any of the oxidative effects and did not impair mitochondrial bioenergetics. Our data provide important insights into the mechanism of mitochondrial toxicity induced by amiodarone. These results may greatly influence the clinical application and toxicity management of these two antiarrhythmic drugs.

Antiproliferative, Ultrastructural, and Physiological Effects of Amiodarone on Promastigote and Amastigote Forms of Leishmania amazonensis

Amiodarone (AMIO), the most frequently antiarrhythmic drug used for the symptomatic treatment of chronic Chagas' disease patients with cardiac compromise, has recently been shown to have also specific activity against fungi, Trypanosoma cruzi and Leishmania. In this work, we characterized the effects of AMIO on proliferation, mitochondrial physiology, and ultrastructure of Leishmania amazonensis promastigotes and intracellular amastigotes. The IC₅₀ values were 4.21 and 0.46 μM against promastigotes and intracellular amastigotes, respectively, indicating high selectivity for the clinically relevant stage. We also found that treatment with AMIO leads to a collapse of the mitochondrial membrane potential (ΔΨm) and to an increase in the production of reactive oxygen species, in a dose-dependent manner. Fluorescence microscopy of cells labeled with JC-1, a marker for mitochondrial energization, and transmission electron microscopy confirmed severe alterations of the mitochondrion, including intense swelling and modification of its membranes. Other ultrastructural alterations included (1) presence of numerous lipid-storage bodies, (2) presence of large autophagosomes containing part of the cytoplasm and membrane profiles, sometimes in close association with the mitochondrion and endoplasmic reticulum, and (3) alterations in the chromatin condensation and plasma membrane integrity. Taken together, our results indicate that AMIO is a potent inhibitor of L. amazonensis growth, acting through irreversible alterations in the mitochondrial structure and function, which lead to cell death by necrosis, apoptosis and/or autophagy.

Anticonvulsant and hypnotic effects of amiodarone

Amiodarone hydrochloride is a potent anti-arrhythmic agent, known as a multiple ion-channel blocker in the heart. Although it has been detected in the rat brain, there are no data related to its central nervous system (CNS) effects. In this study, we evaluated anticonvulsant and hypnotic effects of amiodarone. Convulsions were induced by phentylenetetrazole (PTZ) (100 mg/kg) or caffeine (300 mg/kg) in mice. In both models, amiodarone prolonged both latency period and time to death, and acted as an anticonvulsant drug. It was found to be more effective in the PTZ model than in the caffeine model; none of the animals treated with 150 mg/kg dose amiodarone had died in the PTZ model. For hypnotic effect, sleeping was induced with pentobarbital (35 mg/kg) in rats. Amiodarone dose-dependently increased the sleeping time (677.7%-725.9%). In the sleeping test, all rats in 200 mg/kg amiodarone group died. In conclusion, anticonvulsant and hypnotic effects of amiodarone have shown the depressant effects on CNS. These effects may be dependent on its pharmacological properties.

Amiodarone pretreatment of organ donors exerts anti-oxidative protection but induces excretory dysfunction in liver preservation and reperfusion

The continuous shortage of organs necessitates the use of marginal organs from donors with various diseases, including arrhythmia-associated cardiac failure. One of the most frequently used anti-arrhythmic drugs is amiodarone (AM), which is given in particular in emergency situations. Apart from its anti-arrhythmic actions, AM provides anti-oxidative properties in cardiomyocytes. Thus, we were interested in whether AM donor pretreatment affects the organ quality and function of livers procured for preservation and transplantation. Donor rats were pretreated with AM (5 mg/kg of body weight) 10 minutes before flush-out of the liver with a cold (4 degrees C) histidine-tryptophan-ketoglutarate solution (n = 8). Livers were then stored for 24 hours at 4 degrees C before ex situ reperfusion with a 37 degrees C Krebs-Henseleit solution for 60 minutes in a nonrecirculating system. At the end of reperfusion, tissue samples were taken for histology and Western blot analysis. Animals with vehicle only (0.9% NaCl) served as ischemia/reperfusion controls (n = 8). Additionally, livers of untreated animals (n = 8) not subjected to 24 hours of cold ischemia served as sham controls. AM pretreatment effectively attenuated lipid peroxidation, stress protein expression, and apoptotic cell death. This was indicated by an AM-mediated reduction of malondialdehyde, heme oxygenase-1, and caspase-3 activation. However, AM treatment also induced mitochondrial damage and hepatocellular excretory dysfunction, as indicated by a significantly increased glutamate dehydrogenase concentration in the effluate and decreased bile production. In conclusion, AM donor pretreatment exerts anti-oxidative actions in liver preservation and reperfusion. However, these protective AM actions are counteracted by an induction of mitochondrial damage and hepatocellular dysfunction. Accordingly, AM pretreatment of donors for anti-arrhythmic therapy should be performed with caution.

Hepatotoxicity after intravenous amiodarone

Amiodarone is a class III antiarrhythmic agent with a long half-life which is used to control atrial and ventricular arrhythmias, including atrial flutter and fibrillation. We describe here the case of an elderly woman (77 years of age) who was hospitalized for acute atrial fibrillation, abdominal pain, and dyspnea. In the Emergency Department, treatment with intravenous amiodarone was begun. The following day, the patient developed acute liver damage; improved liver function occurred following the withdrawal of amiodarone. Complete recovery of liver function was documented after three weeks. Unfortunately, the patient died from a severe infectious disease, with multiple organ failure.

Gastroprotective and antioxidant effects of amiodarone on indomethacin-induced gastric ulcers in rats

Reactive oxygen species (ROS) have been implicated in the etiology of indomethacin-induced gastric mucosal damage. This study investigated amiodarone's protective effects against oxidative gastric mucosal damage induced by indomethacin. Amiodarone is a widely used antiarrhythmic agent. We have investigated alterations in the glutathione level, and the activities of antioxidative enzymes [superoxide dismutase, catalase, glutathione s-transferase glutathione reductase and myeloperoxidase], as markers for ulceration process following oral administration of amiodarone and ranitidine in rats with indomethacin-induced ulcers. In the present study we found that 1) amiodarone, lansoprazole and ranitidine reduced the development of indomethacin-induced gastric damages, at a greater magnitude for amiodarone and lansoprazole than for ranitidine; 2) amiodarone and ranitidine alleviated increases in the activities of catalase and glutathione s-transferase enzymes resulting from ulcers; 3) amiodarone and ranitidine ameliorated depressions in the glutathione level and the activities of superoxide dismutase and glutathione reductase enzymes caused by indomethacin administration; and 4) all doses of amiodarone amplified the myeloperoxidase activity resulting from indomethacin-induced gastric ulcers. The results indicate that the gastroprotective activity of amiodarone, which may be linked to its intrinsic antioxidant properties, cannot be attributed to its effect on myeloperoxidase activity.

Amiodarone has anti-inflammatory and anti-oxidative properties: An experimental study in rats with carrageenan-induced paw edema

Amiodarone is a widely used anti-arrhythmic agent. We have investigated alterations in the glutathione (GSH) level and the activities of anti-oxidative enzymes (superoxide dismutase, catalase, glutathione s-transferase and glutathione reductase) and myeloperoxidase, as marker of acute inflammation, following oral administration of amiodarone and diclofenac in rats with carrageenan-induced paw edema. In the present study, we found that 1) Amiodarone reduced the development of carrageenan-induced paw edema, to a greater degree than diclofenac; 2) Amiodarone and diclofenac alleviated increases in the activities of catalase and glutathione s-transferase enzymes resulting from edema; 3) Amiodarone and diclofenac ameliorated depressions in the GSH level and the activities of superoxide dismutase and glutathione reductase enzymes caused by carrageenan injection; and 4) All doses of amiodarone and diclofenac caused an amplification in myeloperoxidase activity resulting from induced paw edema. These results suggest that the anti-inflammatory effect of amiodarone on carrageenan-induced acute inflammation can be attributed to its ameliorating effect on the oxidative damage.

Protective effect of amiodarone but not N-desethylamiodarone on postischemic hearts through the inhibition of mitochondrial permeability transition

Amiodarone is a widely used and potent antiarrhythmic agent that is metabolized to desethylamiodarone. Both amiodarone and its metabolite possess antiarrhythmic effect, and both compounds can contribute to toxic side effects. Here, we compare the effect of amiodarone and desethylamiodarone on mitochondrial energy metabolism, membrane potential, and permeability transition and on mitochondria-related apoptotic events. Amiodarone but not desethylamiodarone protects the mitochondrial energy metabolism of the perfused heart during ischemia in perfused hearts. At low concentrations, amiodarone stimulated state 4 respiration due to an uncoupling effect, inhibited the Ca2+-induced mitochondrial swelling, whereas it dissipated the mitochondrial membrane potential (Deltapsi), and prevented the ischemia-reperfusion-induced release of apoptosis-inducing factor (AIF). At higher concentrations, amiodarone inhibited the mitochondrial respiration and simulated a cyclosporin A (CsA)-independent mitochondrial swelling. In contrast to these, desethylamiodarone did not stimulate state 4 respiration, did not inhibit the Ca2+-induced mitochondrial permeability transition, did not induce the collapse of Deltapsi in low concentrations, and did not prevent the nuclear translocation of AIF in perfused rat hearts, but it induced a CsA-independent mitochondrial swelling at higher concentration, like amiodarone. That is, desethylamiodarone lacks the protective effect of amiodarone seen at low concentrations, such as the inhibition of calcium-induced mitochondrial permeability transition and inhibition of the nuclear translocation of the proapoptotic AIF. On the other hand, both amiodarone and desethylamiodarone at higher concentration induced a CsA-independent mitochondrial swelling, resulting in apoptotic death that explains their extracardiac toxic effect.

Silymarin and vitamin E reduce amiodarone-induced lysosomal phospholipidosis in rats

Several antioxidants have been shown to reduce lysosomal phospholipidosis, which is a potential mechanism of amiodarone toxicity, and prevent amiodarone toxicity by antioxidant and/or non-antioxidant mechanisms. The aim of this study was to test whether the co-administration of two structurally different antioxidants vitamin E and silymarin with amiodarone can reduce amiodarone-induced lysosomal phospholipidosis, and if yes, by reducing the tissue concentration of amiodarone and desethylamiodarone or by their antioxidant action. To this end, male Fischer 344 rats were treated by gavage once a day for 3 weeks and randomly assigned to the following four experimental groups: 1, control; 2, amiodarone (150 mg/(kg per day)); 3, amiodarone (150 mg/(kg per day)) plus vitamin E (100 mg/(kg per day)); 4, amiodarone (150 mg/(kg per day)) plus silymarin (60 mg/(kg per day)) treated groups. Total plasma phospholipid (PL), liver-conjugated diene, thiobarbituric acid reactive substances (TBARSs), amiodarone and desethylamiodarone concentrations were determined and the extent of lysosomal phospholipidosis in the liver was estimated by a semi-quantitative electron microscopic method. Amiodarone treatment increased significantly the liver-conjugated diene (P<0.001), TBARS (P=0.012), plasma total PL (P<0.001) concentrations compared with control. Antioxidants combined with amiodarone significantly decreased the liver-conjugated diene (P<0.001 for both), TBARS (P=0.016 for vitamin E, P=0.053 borderline for silymarin) and plasma total PL (P=0.058 borderline for vitamin E, P<0.01 for silymarin) concentrations compared with amiodarone treatment alone. Silymarin significantly (P=0.021) reduced liver amiodarone, but only tended to decrease desethylamiodarone concentration; however, vitamin E failed to do so. Amiodarone treatment increased lysosomal phospholipidosis (P<0.001) estimated by semi-quantitative electron microscopic method and both antioxidants combined with amiodarone reduced significantly (P<0.001 for both) the amiodarone-induced lysosomal phospholipidosis. In conclusion, silymarin presumably reduced lysosomal phospholipidosis by both antioxidant action and its liver amiodarone concentration decreasing effect, while vitamin E exerted similar effect by antioxidant action alone. Thus, both antioxidant action and inhibition of tissue uptake of amiodarone might have an important role in the preventative effect of antioxidants against amiodarone toxicity.

Concentration dependent mitochondrial effect of amiodarone

Although, the antiarrhythmic effect of amiodarone is well characterized, its effect on post-ischemic heart and cardiomyocytes, as well as the mechanism of its toxicity on extracardiac tissues is still poorly understood. In this study, we analyzed energy metabolism in situ during ischemia-reperfusion in Langendorff-perfused heart model by measuring the high-energy phosphate metabolites using 31P NMR spectroscopy. The toxicity of amiodarone on cardiomyocytes and cell lines of extracardiac origin, as well as direct effect of the drug on mitochondrial functions in isolated mitochondria was also analyzed. Amiodarone, when was present at low concentrations and predominantly in membrane bound form, protected heart and mitochondrial energy metabolism from ischemia-reperfusion-induced damages in Langendorff-perfused heart model. Toxicity of the drug was significantly higher on hepatocytes and pancreatic cells than on cardiomyocytes. In isolated mitochondria, amiodarone did not induce reactive oxygen species formation, while it affected mitochondrial permeability transition in a concentration dependent way. Up to the concentration of 10 microM, the drug considerably inhibited Ca(2+)-induced permeability transition, while at higher concentrations it induced a cyclosporin A independent permeability transition of its own. At concentrations where it inhibited the Ca(2+)-induced permeability transition (IC(50)=3.9+/-0.8 microM), it did not affect, between 6 and 30 microM it uncoupled, while, at higher concentrations it inhibited the respiratory chain. Thus, the concentration dependent nature of amiodarone's effect on permeability transition together with the different sensitivities of the tissues toward amiodarone can be involved in the beneficial cardiac and the simultaneous toxic extracardiac effects of the drug.

Is amiodarone an underrecognized cause of acute respiratory failure in the ICU?

Amiodarone is a commonly used anti-arrhythmic agent, with well-recognized chronic toxicity. Less well known is amiodarone's potential to cause acute lung damage, which can be severe or, occasionally, life-threatening. Lungs that have already been exposed to physical insults, such as the lungs of patients undergoing cardiac surgery, are particularly susceptible to acute pulmonary toxicity (APT). Unfortunately, cardiac surgery is one of the clinical scenarios in which amiodarone is most commonly used. After reviewing the data, and even in the context of difficulties and discrepancies in the existing literature, we contend that there is sufficient evidence of amiodarone's potentially serious side-effect profile in surgical ICU patients to advise continued caution in its use with this severely ill patient group. We suggest that amiodarone has a potentially important, though underrecognized, role in inducing an APT/ARDS in some patients, such as those undergoing cardiac surgery. We also provide a hypothesis to explain the mechanism by which amiodarone causes lung damage.

The effect of quinacrine on oxidative stress in kidney tissue stored at low temperature after warm ischemic injury

Rabbit kidney cortex tissue slices were made ischemic (37 degrees C) for 60 min and then either reperfused in warm (37 degrees C) oxygenated physiologic buffer for 210 min or placed in UW Na gluconate solution (+/- quinacrine; 100 micromol/L) for 18 h followed by warm aerobic reperfusion. Slices were sampled at intervals and analyzed for malondialdehyde (MDA) content by HPLC. Control (nonischemic) slices had no change in MDA content over the duration of the experiment. Hypothermic storage of nonischemic slices did not result in any increase in MDA during reperfusion. Ischemic slices showed significant increases in MDA content during the first 1.5 h of reperfusion and remained elevated for the remainder of the experiment. Hypothermic storage of warm ischemic kidney slices resulted in a significant decrease in MDA content during the storage period. However, MDA content in these slices increased during warm reperfusion and was significantly higher than that in nonischemic controls. Quinacrine added during hypothermic storage of warm ischemic slices significantly decreased slice MDA content during warm reperfusion, an effect which was lost by increasing the storage solution calcium content. This study shows that aerobic hypothermic storage can aid in reducing oxidative stress in warm ischemic kidney tissue during reperfusion. This study suggests that the effects of quinacrine are at the level of the mitochondrion and not as an antioxidant compound.

Amiodarone protects cardiac myocytes against oxidative injury by its free radical scavenging action

BACKGROUND

Oxidative stress plays an important role in the pathophysiology of ischemic heart disease and heart failure, and antioxidants might be beneficial in the treatment of these patients. This study was performed to determine the scavenging effects of amiodarone on oxygen free radicals and its protective effects against oxygen radical-mediated injury in cardiac myocytes.

METHODS AND RESULTS

The formation of the radical spin adduct with hydroxy radical (.OH) in the presence of H(2)O(2) (10 mmol/L) and Fe(3+)-nitrilotriacetate (20 micromol/L) was monitored by electron paramagnetic resonance spectroscopy combined with a spin trapping agent, 5,5-dimethyl pyrroline-N-oxide (DMPO). Amiodarone decreased the intensity of the DMPO-OH signals in a dose-dependent manner (0.1 to 100 micromol/L), whereas other antiarrhythmia drugs such as disopyramide and atenolol had no such effects. Furthermore, amiodarone (10 micromol/L) protected intact adult canine cardiac myocytes against.OH-mediated myocyte injury, as assessed by the degree of morphological change from rod shape to the irreversible hypercontracture state during the exposure of cells to H(2)O(2) and Fe(3+) in vitro.

CONCLUSIONS

Amiodarone can protect cardiac myocytes against oxidative stress-mediated injury by directly scavenging oxygen free radicals. Antioxidant action of amiodarone might potentially contribute to the beneficial effects of this drug in the treatment of patients with ischemic heart disease and congestive heart failure.

Amiodarone-induced disruption of hamster lung and liver mitochondrial function: lack of association with thiobarbituric acid-reactive substance production

Amiodarone (AM) is an efficacious antidysrhythmic agent that is limited clinically by numerous adverse effects. Of greatest concern is AM-induced pulmonary toxicity (AIPT) due to the potential for mortality. Mitochondrial alterations and free radicals have been implicated in the etiology of AM-induced toxicities, including AIPT. Isolated hamster lung and liver mitochondria were assessed for AM-induced effects on respiration, membrane potential, and lipid peroxidation. AM (50-400 microM) stimulated state 4 (resting) respiration at complexes I and II of tightly coupled lung mitochondria, with higher concentrations (200 and 400 microM) resulting in a subsequent inhibition. This biphasic effect of AM (200 microM) was also observed with isolated liver mitochondria. Only inhibition of respiration was observed with AM (50-400 microM) in less tightly coupled lung mitochondria. Based on safranine fluorescence, 200 microM AM decreased lung mitochondrial membrane potential (p < 0.05), while a concentration-dependent (50-200 microM) decrease of membrane potential was observed with liver mitochondria exposed to AM (p < 0.05). Formation of thiobarbituric acid-reactive substances (TBARS) was not altered by AM (50-400 microM) in incubations lasting up to 1 h. These results indicate that lipid peroxidation, as indicated by levels of TBARS, does not play a role in AM-induced alterations in mitochondrial respiration and membrane potential.