1
|
Abstract
Amiodarone has multiple and complex electrophysiological effects that render it a very effective antiarrhythmic drug for the treatment of both, supraventricular and ventricular arrhythmias. Proarrhythmic effects of amiodarone in patients with structural heart disease are rare. However, extracardiac adverse effects occurring in association with amiodarone treatment are frequent and feared. These adverse effects have usually been related to total amiodarone exposure (i. e., dose and duration of treatment). Parallel to a more frequent use of lower amiodarone maintenance doses (100-200 mg/day), the incidence of severe unwanted extracardiac side effects has decreased. High-dose maintenance regiments (daily dose ≥300 mg) are usually obsolete. This paper discusses recommendations regarding the monitoring of cardiac and extracardiac side effects of amiodarone. They need to be regarded by physicians using amiodarone to ensure long-term safety of amiodarone therapy.
Collapse
|
2
|
Habbab LM, Chu FV. Intrapericardial Amiodarone for the Prevention of Postoperative Atrial Fibrillation. J Card Surg 2016; 31:253-8. [DOI: 10.1111/jocs.12700] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Louay M. Habbab
- Division of Cardiac Surgery; Department of Surgery; Hamilton General Hospital; McMaster University; Hamilton Ontario Canada
| | - F. Victor Chu
- Division of Cardiac Surgery; Department of Surgery; Hamilton General Hospital; McMaster University; Hamilton Ontario Canada
| |
Collapse
|
3
|
Ding S, Chen F, Klitzner TS, Wetzel GT. Inhibition of L-type Ca2+ channel current in Xenopus oocytes by amiodarone. J Investig Med 2001; 49:346-52. [PMID: 11478411 DOI: 10.2310/6650.2001.33900] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
BACKGROUND Although amiodarone has been referred to as a class III antiarrhythmic agent, it also possesses electrophysiologic characteristics of the three other classes (classes I and IV and minor class II effects). Previous studies have demonstrated that amiodarone inhibits Ca2+ channel current in intact cardiac myocytes. However, it is not clear whether this response reflects a pure class IV effect (direct Ca2+ channel inhibition) or a class II effect (beta-adrenergic receptor blockade) of amiodarone. METHODS In the current study, the effects of amiodarone on Ca2+ current were studied in the absence of sympathetic regulation using a Xenopus oocyte expression system. The L-type Ca2+ channel alpha1C subunit was coexpressed with the alpha2delta and beta2a subunits in enzymatically digested Xenopus oocytes. Ca2+ currents were recorded using the cut-open oocyte preparation. RESULTS We found that perfusion of 10 microM isoproterenol produced no significant change in peak Ca2+ current (from 223+/-33 to 210+/-29 nA, mean+/-SEM, n=5, P=not significant), indicating the absence of a functional stimulatory sympathetic signal pathway in these oocytes. After 10 minutes of exposure to 10 microM amiodarone, Ca2+ current amplitude was significantly decreased from 174+/-33 to 100+/-26 nA (n=8, P<0.01; control group: 220+/-33 to 212+/-29 nA, n=5, P=not significant). These effects were similar to those of 10 microM nifedipine (201+/-48 to 108+/-48 nA, n=6, P<0.05), a typical Ca2+ channel blocker. On the other hand, neither amiodarone nor nifedipine significantly altered the Ca2+ current activation or inactivation kinetics. CONCLUSIONS These results demonstrate that amiodarone inhibits Ca2+ current in the absence of a functional intrinsic beta-adrenergic stimulatory system and, therefore, represents a true class IV effect.
Collapse
Affiliation(s)
- S Ding
- School of Medicine, University of California at Los Angeles, 90095-7045, USA
| | | | | | | |
Collapse
|
4
|
Abstract
Atrial fibrillation is associated with three major risk of complications: thromboembolism, hemodynamic compromise, and arrhythmogenesis. In patients with chronic atrial fibrillation the incidence of embolization is about 5% per year. The risk of embolism and in particular of stroke can be reduced by warfarin anticoagulation. Aspirin is generally less effective than warfarin, although it is probably more effective than placebo. The hemodynamic complications which may occur during atrial fibrillation are mainly due to the loss of effective atrial contraction, the irregular ventricular rhythm, and the possible excessively rapid ventricular rate. Sudden death is a recognized manifestation of Wolff-Parkinson-White syndrome and is considered to be precipitated by atrial fibrillation in the majority of patients. Torsades de pointes is perhaps the most widely recognized proarrhythmia associated with treatment of atrial fibrillation, especially with 1A antiarrhythmic drugs and sotalol. The chronic treatment with type 1C drugs in 3.5%-5% of patients may induce atrial flutter with 1:1 conduction with significant hemodynamic compromise.
Collapse
Affiliation(s)
- A Capucci
- Division of Cardiology, Ospedale Civile, Piacenza, Italy
| | | | | |
Collapse
|
5
|
Ayers GM, Rho TH, Ben-David J, Besch HR, Zipes DP. Amiodarone instilled into the canine pericardial sac migrates transmurally to produce electrophysiologic effects and suppress atrial fibrillation. J Cardiovasc Electrophysiol 1996; 7:713-21. [PMID: 8856462 DOI: 10.1111/j.1540-8167.1996.tb00579.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
INTRODUCTION We investigated whether amiodarone delivered into the pericardial sac exerted an effect on atrial and ventricular refractoriness, impulse generation, and conduction and on induced atrial fibrillation. METHODS AND RESULTS All animals were anesthetized with alpha-chloralose. After a sternotomy, the pericardium was opened and cradled to produce a "container" of approximately 75 mL. Part I experimental animals received amiodarone, 0.5, 1.0, or 5.0 mg/mL, dissolved in 3 mL polysorbate 80 and 5% dextrose in water (D5W) instilled into their pericardial sac for 3-hour intervals. Part II experimental animals received either 1.0 or 5.0 mg/mL of amiodarone. Control dogs received a pericardial solution of 3 mL polysorbate 80 in D5W. Pre- and postinstillation electrophysiologic studies were performed. In part I, the increase in sinus cycle length, 1:1 AV conduction, and effective refractory period (ERP) of atrium, right ventricular (RV) and left ventricular epicardium, and RV endocardium were significantly greater in animals receiving amiodarone compared with controls. Amiodarone concentrations in the tissue samples were highest in the superficial sites of the atria, sinoatrial node, and ventricular epicardial samples and lowest in the interventricular septum. Only trace concentrations of amiodarone and no desethylamiodarone were found in the blood samples. In part II, atrial ERP significantly increased in the animals receiving amiodarone, and the number of episodes of sustained atrial fibrillation that could be induced decreased. CONCLUSIONS Amiodarone instilled into the pericardial sac migrates transmurally to produce significant electrophysiologic effects at superficial sites and appears to suppress electrically induced atrial fibrillation.
Collapse
Affiliation(s)
- G M Ayers
- Krannert Institute of Cardiology, Indianapolis, Indiana, USA
| | | | | | | | | |
Collapse
|
6
|
Futamura Y. Effect of amiodarone on release of cytokines from mouse alveolar macrophages pretreated with eicosapentaenoic acid. JAPANESE JOURNAL OF PHARMACOLOGY 1995; 69:335-41. [PMID: 8786636 DOI: 10.1254/jjp.69.335] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
I studied the effect of amiodarone, a cationic amphiphilic drug, on the cytokine release and protein kinase C (PKC) activity of mouse alveolar macrophages. In addition, I examined the relationship between amiodarone and eicosapentaenoic acid (EPA) with respect to the cytokine release. The decrease in cell number caused by amiodarone was depressed by pretreatment of the macrophages with EPA for 2 days and co-treatment for 1 day. These changes reflected the potency of EPA to protect against the cell injury elicited by amiodarone. As regards to the cytokine release, amiodarone caused an increase in interleukin (IL)-1 alpha, IL-1 beta and tumor necrosis factor (TNF) alpha release from macrophages. As EPA suppressed this increase in cytokine levels, I considered that the protective effect of EPA may be extended to the acute release of cytokines. PKC activity was increased by amiodarone, and this increase was depressed by EPA. These changes were well-related to the results on cytokine levels in this study, indicating that amiodarone firstly activated PKC, leading to the stimulation of release of cytokines and that pretreatment with EPA prevented these effects. I conclude that mouse alveolar macrophages treated with amiodarone show activated release of cytokines and that EPA depresses these increases, thereby demonstrating EPA's anti-inflammatory effect and protective action against injury of alveolar macrophages.
Collapse
Affiliation(s)
- Y Futamura
- Department of Pharmacology, Toho University School of Medicine, Tokyo, Japan
| |
Collapse
|
7
|
Kodama I, Suzuki R, Kamiya K, Iwata H, Toyama J. Effects of long-term oral administration of amiodarone on the electromechanical performance of rabbit ventricular muscle. Br J Pharmacol 1992; 107:502-9. [PMID: 1422596 PMCID: PMC1907859 DOI: 10.1111/j.1476-5381.1992.tb12774.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
1. The effects of long-term administration of oral amiodarone on transmembrane action potential and contraction of ventricular muscle were investigated in rabbits. 2. ECGs of rabbits that received oral amiodarone 50 mg or 100 mg kg-1 daily for 4 weeks, showed a significant prolongation of RR, QT and corrected QT (QTc) intervals, whereas PQ and QRS were unaffected. Serum and myocardial tissue amiodarone concentrations were 0.14-0.18 micrograms ml-1 and 1.47-3.63 micrograms g-1 wet wt. respectively. 3. Right ventricular papillary muscles isolated from treated rabbits were characterized by a moderate prolongation of action potential duration (APD) compared with controls. A slight decrease of the maximum upstroke velocity (Vmax) was also observed at the higher dose. The APD prolongation by chronic amiodarone, unlike acute effects of sotalol, E-4031, Cs+ and 4-aminopyridine, did not show marked reverse use-dependence. 4. APD and Vmax restitution following slow basic stimuli (0.03 Hz) were unaffected by chronic treatment with amiodarone. 5. Acute application of amiodarone (10 microM) caused a significant decrease in APD and developed tension, as well as a marked use-dependent Vmax inhibition with fast recovery kinetics. 6. These findings suggest that a major and consistent electro-physiological effect of chronic amiodarone is repolarization delay (Class-III action) showing minimal frequency-dependence. However, when amiodarone above a certain concentration is present in the extracellular space, a fast kinetic Class-I action would be added as an acute effect.
Collapse
Affiliation(s)
- I Kodama
- Department of Circulation, Nagoya University, Japan
| | | | | | | | | |
Collapse
|
8
|
Abstract
The antiarrhythmic properties of amiodarone at the ventricular level were discovered in the early 1970s. The unanimously recognised efficacy of amiodarone includes a weak negative inotropic effect and compensatory vasodilatory properties, making amiodarone particularly suitable for treating the potentially malignant arrhythmias associated with organic disease. In a review of 611 hospitalised patients on amiodarone, and 353 patients in whom the drug had been prescribed, over a 52-month period in our 60-bed department, we noted that amiodarone was prescribed in 53% of patients for arrhythmias and in 47% of patients for coronary insufficiency. Ventricular arrhythmias represented 13% of the rhythmic indications. These indications differ from those in the USA. The efficacy (70 to 90%) of amiodarone in ventricular extrasystoles has been shown in open studies. In coronary patients, the antiarrhythmic activity of amiodarone is superior to that of propranolol. However, there has been no controlled study because the need for a loading dosage, and the electrocardiographic effects render such studies difficult. After myocardial infarction, ventricular arrhythmias constitute a significant risk factor independently of prognosis; amiodarone may be useful in this indication, and studies of the European Myocardial Infarction Amiodarone Trial (EMIAT) type will examine its value here. Since 1973, it has been recognised that amiodarone can prevent ventricular tachycardia in 55 to 89% of patients in the clinical situation. After a long-standing controversy, the positive predictive value of programmed stimulation has finally been agreed on. In hypertrophic cardiomyopathy, retrospective studies suggest a reduction in mortality in patients treated with amiodarone. By contrast, the value of amiodarone in dilated cardiomyopathy requires more intensive investigation. We consider amiodarone to be indicated in ventricular arrhythmic complexes, particularly if they are associated with an ejection fraction of less than 35% and/or atrial fibrillation. The value of amiodarone in arrhythmias associated with heart failure needs to be evaluated. In conclusion, amiodarone is a powerful antiarrhythmic agent but, because of the possibility of dose- and duration-dependent side effects, evaluation of the risk: benefit ratio in each indication is needed.
Collapse
Affiliation(s)
- S Levy
- Department of Cardiology, Hôpital Nord, University of Aix, Marseille, France
| |
Collapse
|
9
|
Naccarelli GV, Rinkenberger RL, Dougherty AH, Fitzgerald DM. Adverse effects of amiodarone. Pathogenesis, incidence and management. MEDICAL TOXICOLOGY AND ADVERSE DRUG EXPERIENCE 1989; 4:246-53. [PMID: 2671595 DOI: 10.1007/bf03259911] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Amiodarone is an extremely effective antiarrhythmic agent for the treatment of both life-threatening ventricular arrhythmias and refractory supraventricular tachyarrhythmias. Subjective minor side effects are common with amiodarone but rarely require discontinuation of therapy and are often handled by dose reduction. Serious end-organ toxicity, including pulmonary fibrosis and drug-induced hepatitis, have been the most common indications for discontinuing amiodarone therapy in these patients.
Collapse
Affiliation(s)
- G V Naccarelli
- Division of Cardiology, University of Texas Medical School, Houston
| | | | | | | |
Collapse
|
10
|
Affiliation(s)
- T A Mattioni
- Department of Medicine, Northwestern University School of Medicine, Chicago, IL 60611
| | | | | | | |
Collapse
|
11
|
Vrobel TR, Miller PE, Mostow ND, Rakita L. A general overview of amiodarone toxicity: its prevention, detection, and management. Prog Cardiovasc Dis 1989; 31:393-426. [PMID: 2652188 DOI: 10.1016/0033-0620(89)90016-9] [Citation(s) in RCA: 86] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Although amiodarone is a highly effective antiarrhythmic agent, it has a high incidence of side effects, some of which can be serious or even lethal. With close monitoring, side effects can be found in essentially all patients, but fortunately most of these are mild and well tolerated. Furthermore, many will respond to dosage reduction in a relatively short period of time, ie, days to weeks, which is remarkable considering the long period of time amiodarone has been shown to persist in tissues. There is reasonable evidence that toxicity, particularly the early toxic manifestations with large loading dosages, can be favorably modified by reducing the dosage. Similarly, reducing the maintenance dosage will, in most instances, reduce or eliminate most toxic manifestations. The mechanisms of toxic effects are uncertain, but suggestive evidence exists for and against both an immunologic reaction and an intracellular lysosomal lipoidosis. Principles of use of amiodarone should include individualizing administration of dosages for each patient due to the unusual pharmacokinetic properties of this drug and continuous long-term attempts at using the lowest effective dosage. There are no definite tests that predict amiodarone efficacy or toxicity, but the serum level can be used as a rough guide of absorption and distribution in the attempt to minimize the maintenance dosage. No guidelines regarding screening tests for toxicity can be made at this time since great variability in these tests has been reported, and no evidence exists for their benefit in preventing adverse effects to amiodarone. However, follow-up testing at the intervals noted in the package insert are reasonable and important. The possibility of interactions with drugs already reported and with others not yet reported should always be kept in mind, and appropriate monitoring for clinical evidence of toxicity due to the concomitantly used drugs should be undertaken. Amiodarone can have a tremendous beneficial effect in the proper circumstances, but it is a drug that should command utmost respect because of its side effects and requires constant vigilance from any physician wishing to use it.
Collapse
Affiliation(s)
- T R Vrobel
- Department of Medicine, Cleveland Metropolitan General Hospital, Ohio 44109
| | | | | | | |
Collapse
|
12
|
Skluth H, Grauer K, Gums J. Ventricular arrhythmias. An assessment of newer therapeutic agents. Postgrad Med 1989; 85:137-8, 141-8, 153. [PMID: 2496401 DOI: 10.1080/00325481.1989.11700694] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- H Skluth
- Department of Pharmacy Practice, College of Pharmacy, University of Florida, Gainesville
| | | | | |
Collapse
|
13
|
Greene HL. The efficacy of amiodarone in the treatment of ventricular tachycardia or ventricular fibrillation. Prog Cardiovasc Dis 1989; 31:319-54. [PMID: 2646655 DOI: 10.1016/0033-0620(89)90029-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- H L Greene
- Electrophysiology Laboratory, Harborview Medical Center, University of Washington, Seattle 98104
| |
Collapse
|
14
|
Singh BN, Venkatesh N, Nademanee K, Josephson MA, Kannan R. The historical development, cellular electrophysiology and pharmacology of amiodarone. Prog Cardiovasc Dis 1989; 31:249-80. [PMID: 2642623 DOI: 10.1016/0033-0620(89)90033-9] [Citation(s) in RCA: 87] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- B N Singh
- Department of Cardiology, Wadsworth VA Hospital, Los Angeles, CA 90073
| | | | | | | | | |
Collapse
|
15
|
Sheldon RS, Mitchell LB, Duff HJ, Wyse DG, Manyari DE. Right and left ventricular function during chronic amiodarone therapy. Am J Cardiol 1988; 62:736-40. [PMID: 3421174 DOI: 10.1016/0002-9149(88)91213-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Although chronic therapy with amiodarone is an effective means of suppressing ventricular tachycardia, its long-term effects on ventricular function have not been evaluated. Therefore, left ventricular (LV) and right ventricular (RV) ejection fraction (EF) as well as wall motion score were assessed in 21 patients with ventricular tachycardia before therapy and after 2, 6, 10 and 20 weeks of amiodarone therapy. Serum amiodarone levels after 2, 6, 10 and 20 weeks were 1.9 +/- 0.7, 1.7 +/- 0.6, 1.5 +/- 0.6 and 1.5 +/- 0.7 micrograms/ml, respectively. Drug therapy did not significantly affect the mean LVEF (0 weeks 38 +/- 17, 2 weeks 40 +/- 17, 6 weeks 40 +/- 17, 10 weeks 41 +/- 18 and 20 weeks 40 +/- 18%) or the mean RVEF. Neither LV wall motion score nor RV wall motion score were changed significantly during amiodarone therapy. Fourteen patients had a drug-free LVEF less than 40% (mean 28 +/- 7%). Ventricular function in this subgroup was not impaired after 20 weeks of amiodarone therapy (drug-free LVEF 28 +/- 7%, 20 weeks LVEF 29 +/- 9%; drug-free RVEF 42 +/- 13%, 20 weeks RVEF 41 +/- 12%). Ten patients who were evaluated 34 +/- 6 months after initiation of amiodarone therapy had no significant change in LVEF (drug-free 37 +/- 20%, 34 months 43 +/- 20%). Ventricular functional reserve was assessed after 20 weeks of therapy.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
Affiliation(s)
- R S Sheldon
- Department of Medicine, University of Calgary, Canada
| | | | | | | | | |
Collapse
|
16
|
|
17
|
Reasor MJ, Ogle CL, Walker ER, Kacew S. Amiodarone-induced phospholipidosis in rat alveolar macrophages. THE AMERICAN REVIEW OF RESPIRATORY DISEASE 1988; 137:510-8. [PMID: 2830811 DOI: 10.1164/ajrccm/137.3.510] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Humans treated with the antiarrhythmic drug amiodarone may develop pulmonary toxicity accompanied by the presence of alveolar macrophages (AM) containing lamellar inclusions. This cellular response is indicative of the development of a drug-induced phospholipidosis. To characterize this response of the AM, Fischer-344 rats were treated with amiodarone, and the macrophages were recovered by pulmonary lavage. The development of phospholipidosis was dose- and time-dependent and was reversible. Daily treatment for 1 wk (5 days/wk) at 150 mg/kg resulted in a 5-fold increase in total phospholipid in the cells. Phospholipid levels were increased only slightly more through 9 wk of treatment. Cells were filled with lamellar inclusions and contained areas of amorphous granular and membranous material. Individual classes of phospholipids were all increased during the development of phospholipidosis. When expressed as mumol/10(7) cells, phosphatidylcholine demonstrated the largest increase. Levels of amiodarone and its major metabolite, desethylamiodarone, increased in AM in parallel with the increase in phospholipid. From 3 days through 9 wk of treatment, the level of desethylamiodarone was always higher than that of amiodarone. Treatment with desethylamiodarone also induced phospholipidosis in AM. Administration of phenobarbital along with amiodarone for 1 wk caused a reduction in the levels of amiodarone, desethylamiodarone, and phospholipid in the cells. The molar ratio of amiodarone to phospholipid was decreased, whereas the molar ratio of desethylamiodarone to phospholipid remained unchanged. Taken together, the results indicate that, along with amiodarone, desethylamiodarone and/or its metabolites may play an important role in the phospholipidosis induced in AM when rats are treated with amiodarone.
Collapse
Affiliation(s)
- M J Reasor
- Department of Pharmacology and Toxicology, West Virginia University Medical Center, Morgantown 26506
| | | | | | | |
Collapse
|
18
|
Nattel S, Davies M, Quantz M. The antiarrhythmic efficacy of amiodarone and desethylamiodarone, alone and in combination, in dogs with acute myocardial infarction. Circulation 1988; 77:200-8. [PMID: 2446801 DOI: 10.1161/01.cir.77.1.200] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Antiarrhythmic activity of amiodarone's desethyl metabolite, which accumulates during oral amiodarone therapy, has been postulated to explain the delayed onset of antiarrhythmic effects during long-term amiodarone therapy. To determine their relative antiarrhythmic efficacy, amiodarone and its desethyl metabolite, desethylamiodarone, were administered to mongrel dogs with ventricular tachycardia 24 hr after ligation of the left anterior descending coronary artery. Cumulative doses of amiodarone, desethylamiodarone, a combination of amiodarone and desethylamiodarone, or the vehicle for drug administration were given at 1 hr intervals. Both amiodarone and desethylamiodarone suppressed ventricular arrhythmias in a dose-dependent fashion. The metabolite, however, was more potent with a 50% effective concentration for suppression of premature ventricular complexes of 1.4 mg/liter compared with 4.6 mg/liter for the parent compound. Plasma and myocardial drug concentrations were similar to those measured during long-term amiodarone therapy in man, with desethylamiodarone producing greater myocardial concentrations than amiodarone for a given plasma concentration. Coadministration of the metabolite along with the parent drug resulted in suppression of arrhythmias at lower doses of amiodarone than when the latter was administered alone, and concentration-response analysis indicated an additive antiarrhythmic effect. These experiments suggest that the accumulation of desethylamiodarone that occurs with long-term oral amiodarone therapy contributes importantly to the antiarrhythmic effects of the drug, and may account for the gradual increase in antiarrhythmic action during the course of amiodarone therapy.
Collapse
Affiliation(s)
- S Nattel
- Department of Pharmacology, McGill University, Montreal, Quebec, Canada
| | | | | |
Collapse
|
19
|
Fan K, Bell R, Eudy S, Fullenwider J. Amiodarone-associated pulmonary fibrosis. Evidence of an immunologically mediated mechanism. Chest 1987; 92:625-30. [PMID: 3308345 DOI: 10.1378/chest.92.4.625] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
A case of pulmonary fibrosis attributed to amiodarone was studied immunologically and morphologically. A specific antibody of the IgG class was identified in the serum of this patient which reacted with the patient's own lung tissue. The immunoglobulin did not react with normal lung tissue nor was there evidence of reaction with lung tissue from patients with pulmonary fibrosis but without a history of amiodarone therapy. The patient probably developed a humoral antibody response to a lung-amiodarone complex with the amiodarone acting as a hapten which bound in vivo to the lung tissue. The subsequent antibody-antigen reaction stimulated a proliferation of pulmonary fibroblasts and probably enhanced the fibro-collagen deposition in the lung.
Collapse
Affiliation(s)
- K Fan
- Department of Pathology, John L. McClellan Memorial Veterans Hospital, Little Rock
| | | | | | | |
Collapse
|
20
|
Duenas-Laita A, Barry MG, MacMathuna P, Feely J. Effects of chronic treatment with amiodarone on hepatic demethylation and cytochrome P450. J Pharm Pharmacol 1987; 39:757-9. [PMID: 2890749 DOI: 10.1111/j.2042-7158.1987.tb06988.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The effect of chronic treatment with amiodarone on hepatic oxidative metabolism using an in-vivo [14C]aminopyrine breath test and on hepatic cytochrome P450 was examined in Wistar rats. Aminopyrine demethylation was significantly impaired but returned to pretreatment values following amiodarone for 4 weeks. In contrast the levels of cytochrome P450 were significantly depressed during treatment and at 4 weeks following treatment. While an inhibitory effect on oxidative metabolism may explain the reported drug interactions with amiodarone, the discrepancy between its in-vivo effects and cytochrome P450 levels may suggest the development of 'compensatory' extra-hepatic site of drug metabolism.
Collapse
Affiliation(s)
- A Duenas-Laita
- Department of Pharmacology and Therapeutics, Trinity College, University of Dublin, Ireland
| | | | | | | |
Collapse
|
21
|
Fain ES, Lee JT, Winkle RA. Effects of acute intravenous and chronic oral amiodarone on defibrillation energy requirements. Am Heart J 1987; 114:8-17. [PMID: 3604876 DOI: 10.1016/0002-8703(87)90300-0] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Amiodarone is commonly used with the automatic implantable defibrillator to treat recurrent ventricular tachyarrhythmias. The effects of acute intravenous and chronic oral amiodarone on the energy requirements for successful defibrillation were evaluated in 12 dogs chronically instrumented with right atrial spring and left ventricular patch defibrillation electrodes. Multiple shocks of varying energy were applied in balanced random order to construct curves of percent successful defibrillation vs energy (DF curves) on each test day. Dogs were studied on days 1, 11, 18, 25, and 32. On day 11, DF curves were determined before and after infusing saline (n = 6) or amiodarone (n = 6), 10 mg/kg loading and 0.33 mg/kg/min maintenance doses. Dogs administered intravenous amiodarone were continued on oral drug (300 mg twice daily) for the remainder of the study. Data were analyzed by logistic regression and the energy required for 50% (E50) and 80% (E80) successful defibrillation were compared. Differences between controls and animals receiving chronic oral amiodarone were not significant on any day. After acute intravenous infusion, dogs given amiodarone had a 21.7 +/- 12.8% decrease in E50 (p less than 0.01) and a 19.7 +/- 17.8% decrease in E80 (p less than 0.05), while controls had an 11.4 +/- 30.5% increase (p = NS) in E50 and 6.30 +/- 30.5 increase in E80 (p = NS). It is concluded that the energy required for successful defibrillation is decreased by acute intravenous amiodarone, while chronic oral administration has no significant effect.
Collapse
|
22
|
Kay GN, Pryor DB, Lee KL, Harrell FE, Pressley JC, Gilbert MR, German LD. Comparison of survival of amiodarone-treated patients with coronary artery disease and malignant ventricular arrhythmias with that of a control group with coronary artery disease. J Am Coll Cardiol 1987; 9:877-81. [PMID: 3558986 DOI: 10.1016/s0735-1097(87)80245-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Although amiodarone is effective in the treatment of ventricular arrhythmias, it is associated with serious toxic effects. In addition, the prognosis of patients with malignant ventricular arrhythmias and coronary artery disease treated with amiodarone remains poor. The survival of 54 consecutive patients with angiographically documented coronary artery disease and symptomatic ventricular tachycardia or ventricular fibrillation treated with amiodarone was compared with that of 5,125 medically treated patients with coronary artery disease. The amiodarone group was older, with worse left ventricular function and more peripheral and cerebrovascular disease. The 1 year survival probability was 0.73 for the amiodarone group and 0.94 for the control coronary artery disease group. At 2 years of follow-up, the survival probabilities were 0.60 and 0.90 for the amiodarone and the control group, respectively. When the survival curves were adjusted for group differences in baseline prognostic characteristics (integrated as a previously published hazard score), there was no difference in the prognosis of the two groups. These findings suggest that treatment with amiodarone of malignant ventricular arrhythmias associated with coronary artery disease maintains patients on an underlying survival curve determined by the degree of myocardial dysfunction, clinical characteristics and coronary anatomy, and that amiodarone does not have a deleterious effect on survival.
Collapse
|
23
|
Abstract
Clinical and laboratory features of 99 patients receiving long-term amiodarone therapy were analyzed to determine which individuals may be at a high risk for developing amiodarone-induced thyroid dysfunction. The group of 68 men and 31 women was followed up for an average of 27 months (range 3 to 60). There were no differences in age, sex, dose of amiodarone, type or severity of underlying heart disease or baseline serum thyroxine levels in patients who developed hypothyroidism (n = 32) or hyperthyroidism (n = 5) or remained euthyroid (n = 62). Baseline serum thyrotropin levels were statistically higher in patients who became hypothyroid, but there was considerable overlap with the other patient groups. Serum reverse triiodothyronine (reverse T3), which has been suggested to be a marker of amiodarone efficacy, correlated directly with serum thyroxine levels, and was not an independent variable. There was no pattern to the time course for development of thyroid dysfunction, which occurred in 49% of those followed up and developed as early as 1 month or, in one individual, as late as after 3 years of amiodarone therapy. There are few guidelines for replacement therapy in patients with amiodarone-induced hypothyroidism. L-thyroxine dosage was adjusted cautiously in these high risk individuals to achieve serum thyroxine levels within the reference range of euthyroid individuals taking amiodarone: the mean dosage required was 136 micrograms/day. Normalization of serum thyrotropin (TSH) would have required doses of L-thyroxine that were judged to be excessively high.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
|
24
|
Venkatesh N, Somani P, Bersohn M, Phair R, Kato R, Singh BN. Electropharmacology of amiodarone: absence of relationship to serum, myocardial, and cardiac sarcolemmal membrane drug concentrations. Am Heart J 1986; 112:916-22. [PMID: 3776818 DOI: 10.1016/0002-8703(86)90300-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Plasma concentrations are often of major consideration in the evaluation of therapeutic efficacy of cardiovascular drugs. This approach is based on the assumptions that the concentration of the drug in the cardiac muscle is in equilibrium with the plasma drug level and that pharmacologic efficacy is proportional to the myocardial drug concentration. The more pronounced pharmacologic efficacy of amiodarone following chronic administration, despite low plasma drug concentrations, and the lesser effects of the drug after acute intravenous administration, when drug levels are maximum, has not been explained on the basis of the pharmacokinetic behavior of the drug. Data obtained from the transmembrane action potential recordings from rabbit ventricular myocardium were therefore correlated with drug concentrations in the serum, myocardium, and myocardial sarcolemma following acute intravenous administration and after 4 weeks of oral administration of 20 mg/kg/day of amiodarone. Following 15 minutes of acute drug administration, when amiodarone concentrations were maximal in the serum (4.72 +/- 1.23 micrograms/ml), cardiac muscle (34.5 +/- 7.6 micrograms/gm), and sarcolemma (1.94 mg/gm protein), the electrophysiologic changes were insignificant. However, following chronic treatment, when levels of amiodarone were low in the serum (0.05 +/- 0.01 micrograms/ml amiodarone, 0.25 +/- 0.08 micrograms/ml desethylamiodarone), cardiac muscle (1.91 +/- 0.9 micrograms/gm amiodarone, 1.35 +/- 1.33 micrograms/gm desethylamiodarone), and myocardial membranes (0.043 mg/gm protein [amiodarone], 0.097 mg/gm protein [desethylamiodarone], there was a 54.3% increase in action potential duration at 90% repolarization (p less than 0.01) and 65% increase in the effective refractory period (p less than 0.01) of rabbit ventricular myocardium.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
|
25
|
Naccarelli GV, Rinkenberger RL, Dougherty AH, Giebel RA. Amiodarone: pharmacology and antiarrhythmic and adverse effects. Pharmacotherapy 1985; 5:298-313. [PMID: 2934688 DOI: 10.1002/j.1875-9114.1985.tb03434.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Amiodarone is a benzofuran derivative that has been effective for the treatment of both supraventricular and ventricular tachyarrhythmias. It has a large volume of distribution, moderate bioavailability and a long half-life. Its pharmacokinetics are not well understood and its tissue distribution is not typical of a 2-compartment model. Due to ocular, dermatologic, gastrointestinal, neurologic, cardiovascular, thyroid and pulmonary toxicity, amiodarone should be reserved for use in patients with refractory and/or life-threatening arrhythmias.
Collapse
|