Amiodarone--benefits and risks in perspective

Bisaramil and antiarrhythmics as inhibitors of free radical generation

The aim of this study was to investigate the effect of bisaramil--an antiarrhythmic drug under clinical trials-on free radical generation of isolated polymorph neutrophil granulocytes (PMN) and furthermore to compare its activity to that of well-known antiarrhythmics which have different modes of action. PMNs were isolated from healthy beagle dogs, and superoxide radical generation was induced by phorbol-myristate-acetate. Stimulated free radical generation capacity of PMNs and the time lag necessary for the initiation of free radical production were measured. All compounds were used at the concentrations of 10, 25, 50, 75, 100 micrograms ml-1. None of the antiarrhythmics stimulated by itself the free radical generation. Bisaramil exerted concentration dependent inhibitory effect on PMA-stimulated free radical generation and prolonged the time lag concentration dependently. At the investigated concentration range of antiarrhythmics only propafenon, mexiletine and diltiazem showed similar activity to bisaramil, but clear concentration dependency could not be seen in any of the cases. According to the results of this study inhibition of the stimulated free radical production of isolated PMNs cannot be closely connected merely to either membrane stabilizing or Ca-antagonistic activity of drugs. In vitro and earlier measured in vivo inhibitory action of bisaramil on free radical generation indicate a possible cardioprotective effect existing independently from its antiarrhythmic one. This observation may be important in outlining of the clinical indication field of bisaramil, and may be useful in the treatment of reperfusional damage.

Effect of amiodarone on mortality after myocardial infarction: a double-blind, placebo-controlled, pilot study

OBJECTIVES

The goal of this study was to evaluate the effect of amiodarone on mortality, ventricular arrhythmias and clinical complications in high risk postinfarction patients.

BACKGROUND

No therapy has been shown to reduce sudden death in patients ineligible to receive beta-adrenergic blocking agents after myocardial infarction.

METHODS

Patients who were not eligible to receive beta-blockers were randomized to receive amiodarone (n = 305) or placebo (n = 308) for 1 year.

RESULTS

There were 21 deaths in the amiodarone group compared with 33 in the placebo group (odds ratio 0.62, 95% confidence interval [CI] 0.35 to 1.08, p = 0.095). There were two noncardiac deaths in the amiodarone group and none in the placebo group; thus, the difference in cardiac mortality (19 vs. 33, respectively) was statistically significant (odds ratio 0.55, 95% CI 0.32 to 0.99, p = 0.048). There was a significant decrease in Lown class 4 ventricular arrhythmias (7.5% vs. 19.7%, respectively, p < 0.001). Adverse effects developed in 30% of amiodarone-treated patients and 10% of placebo-treated patients. Pulmonary toxicity, which was mild and reversible, occurred in only one patient in the amiodarone group but in no patient in the placebo group.

CONCLUSIONS

This trial demonstrated a significant reduction in cardiac mortality and ventricular arrhythmias with amiodarone treatment. However, given the wide confidence intervals and borderline statistical significance of our trial, larger trials are needed to confirm or refute this view.

Rapid control of refractory atrial tachyarrhythmias with high-dose oral amiodarone

To shorten the delay in the onset of antiarrhythmic effect when using amiodarone for the conversion of refractory atrial tachyarrhythmias to sinus rhythm, 19 patients were given oral amiodarone according to a high-dose loading protocol. In 18 of 19 patients (95%), sinus rhythm was restored 36 hours (range, 0 to 96 hours) after starting amiodarone. The conversion occurred as a result of amiodarone therapy alone within 48 hours in 12 patients (63%), and by amiodarone therapy plus electrical cardioversion at 48 to 96 hours in six patients (32%). Minor side effects were noted in eight patients (42%). No major side effects were encountered. The length of hospital stay after initiating amiodarone therapy was 3.6 days (range, 2 to 5 days). High-dose oral amiodarone loading is a safe and effective method for the rapid conversion of atrial tachyarrhythmias to sinus rhythm.

Rapid effectiveness of prednisone and thionamides combined therapy in severe amiodarone iodine-induced thyrotoxicosis. Comparison of two groups of patients with apparently normal thyroid glands

Treatment of amiodarone iodine-induced thyrotoxicosis is often unsuccessful. Nevertheless, severe forms require a rapidly efficient therapy. Twelve patients with severe amiodarone iodine-induced thyrotoxicosis, as demonstrated on clinical and biological findings, were studied. After amiodarone withdrawal, 6 patients (group A) were treated with thionamides alone (carbimazole 60 mg daily and benzylthiouracile 1.5 g daily), and 6 patients (group B) received in addition to the same antithyroid drugs prednisone, 0.50 to 1.25 mg/kg/day for 40 days; in group A, T4 levels did not change over the study period of 40 days; T3 levels decreased only after 30 days; clinical status did not improve. In group B: T3 and T4 levels decreased dramatically at 10 days of treatment, to values significantly lower than in group A; clinical improvement occurred mainly in patients treated with high doses of prednisone; elevated thyroglobulin levels diminished rapidly. Improvement was maintained after cessation of prednisone. The rapid effect of prednisone suggests an impairement of proteolysis of thyroglobulin possibly due to a lysosomal action.

Amiodarone pulmonary toxicity: prospective evaluation of serial pulmonary function tests

Pulmonary toxicity developed in 15 (17%) of 89 patients treated with amiodarone during a follow-up period of 2 weeks to 54 (mean 20 +/- 15) months. Prospective evaluation of serial pulmonary function tests in 67 patients demonstrated both a significant decrease from baseline in three of six variables in patients with toxicity at the time of diagnosis and a significant difference compared with the same variables in patients without toxicity. The most significant of these was the diffusing capacity for carbon monoxide (DLCO). An individual decrease in DLCO greater than or equal to 15% gave an optimal sensitivity of 100% and a specificity of 89% for the diagnosis of pulmonary toxicity. However, a decrease in DLCO greater than or equal to 15% did not alone warrant a change in therapy in asymptomatic patients. Although higher maintenance doses of amiodarone appeared to be related to the development of this complication, an abnormal baseline DLCO (less than 60% of predicted) with or without an initial abnormal chest roentgenogram did not predispose to pulmonary toxicity.

Amiodarone in the management of cardiac arrhythmias: current concepts

This article reviews current information on the clinical pharmacology, therapeutic utility, and adverse reactions of amiodarone, with emphasis on guidelines for its rational use.

Combination therapy for cardiac arrhythmias

Combinations of antiarrhythmic agents are often used when single agents are ineffective, only partly effective or poorly tolerated. The theoretical and experimental basis for combination therapy for arrhythmias is the dissimilar electrophysiologic properties of antiarrhythmic agents. Until more is known about the mechanism of drug synergism and drug interactions, the experience gained clinically remains essential to our understanding. Published reports contain numerous data on the effectiveness of various combinations of antiarrhythmic agents, including combinations of class I agents, the combination of a class I agent and a beta-blocking agent or amiodarone, and combinations including a calcium-antagonist agent. Adverse drug interactions, however, can occur, and combinations of certain agents must be avoided or used with caution.

Pharmacokinetics and pharmacodynamics of antiarrhythmic agents in patients with congestive heart failure

Changes in the pharmacokinetics of antiarrhythmic agents may be anticipated in patients with congestive heart failure (CHF), although the magnitude or direction of change is not always predictable. Factors complicating antiarrhythmic therapy in patients with CHF include both physiologic changes resulting from the disease state and unwanted effects of drug therapy for CHF. The volume of distribution is often significantly decreased (by as much as 50%) and loading doses should be reduced proportionately. Decreased blood flow to the liver and kidneys and decreased hepatic drug-metabolizing activity serve to diminish drug clearance. In some cases, simultaneous decreases in volume of distribution and clearance may result in little, if any, change in elimination half-life, despite higher plasma concentrations. Conversely, the elimination half-life of antiarrhythmic agents may be doubled in patients with CHF, necessitating a reduction in dosage. In the latter case, the time needed to reach steady state is lengthened, so that premature escalation of dosage may lead to excessive drug accumulation. In terms of their pharmacodynamics, most antiarrhythmic agents have a degree of negative inotropic effect at some concentration, and patients with reduced myocardial reserve are especially vulnerable to these effects. Some of the newer agents (such as tocainide, mexiletine, and encainide) appear to cause only minimal myocardial depression. Potential complications during therapy with all antiarrhythmic agents that are of special concern in patients with CHF include diuretic-induced hypokalemia, proarrhythmia, and possible interactions with cardiac glycosides and other drugs. Therapy for patients with CHF should be initiated with low doses of the agent selected, and the dosage carefully titrated while the patient is monitored, to confirm both efficacy and the absence of adverse effects. During subsequent outpatient therapy the patient should be carefully observed for sign of unexpected reactions, toxicity, or electrolyte imbalance.

Effects of amiodarone and thyroid dysfunction on myocardial calcium, serum calcium and thyroid hormones in the rat

1 Myocardial calcium content was found to be elevated and serum calcium reduced in hypothyroid rats. 2 Treatment of rats with amiodarone at either 30 mg kg-1 or 150 mg kg-1 daily did not result in any significant changes in myocardial or serum calcium. 3 The administration of amiodarone to hypothyroid rats attenuated the changes in serum but not myocardial calcium, suggesting that amiodarone may exert a thyroid hormone-like effect in the hypothyroid state. 4 The administration of amiodarone to thyroid hormone-treated rats resulted in attenuation of the effects on serum calcium and calculated intracellular calcium; this was consistent with an antagonistic interaction between amiodarone and thyroid hormones. 5 Administration of amiodarone resulted in significant changes in circulating thyroid hormone levels in the rat; triiodothyronine was reduced and basal thyrotrophin elevated compared to euthyroid controls. Serum thyroxine was not changed; this is in contrast to the effects in man. 6 Amiodarone does not exert its anti-arrhythmic action via changes in total myocardial calcium content in the euthyroid rat; nonetheless the described interactions between the drug and thyroid hormones may be involved in its mechanism of action.

Development of congestive heart failure and alterations in left ventricular function in patients with sustained ventricular tachyarrhythmias treated with amiodarone

The interaction between the efficacy and tolerance of amiodarone and the degree of left ventricular (LV) dysfunction was assessed in 126 patients with sustained ventricular tachyarrhythmias. In all patients radionuclide angiographic LV ejection fraction (EF) was measured before and after 8 to 12 months of amiodarone therapy. At baseline mean EF was 25 +/- 13% and 86 patients had an EF of 30% or less. In patients receiving amiodarone at steady state, there was a small but significant increase in EF (23 to 26%, p less than 0.05). Congestive heart failure (CHF) was present in 43 patients before amiodarone therapy. In 16 patients new (9 patients) or worsened (7 patients) CHF developed during the first year of amiodarone therapy. Development of CHF was not consistently related to a change in EF or heart rate. The clinical efficacy and tolerance of amiodarone were affected by the baseline EF and development of CHF. Efficacy and tolerance was 80% in patients with an EF of more than 30% and 60% in those with an EF of 30% or less. Among the 16 patients in whom new or worsened CHF developed, 6 (38%) died and 9 (56%) had recurrent ventricular tachyarrhythmias. Both baseline EF and development of CHF during amiodarone treatment significantly affect the prognosis in patients with ventricular tachyarrhythmias.

Long-term tolerance of amiodarone treatment for cardiac arrhythmias

For the 5-year period 1979 to 1983, 242 patients were followed up who had received amiodarone treatment, 156 for supraventricular tachycardia (SVT) and 86 for ventricular arrhythmias. Five patients were lost to follow-up overseas; the rest were followed to cessation of therapy, death or recent review for a mean of 24 +/- 15 months. Male/female incidence was 1.8:1 and mean age was 58 years (range 4 to 88). Half the group had impaired left ventricular function. Adverse effects were recorded in 59% of the patients and led to drug withdrawal in 26% of the total group. In contrast, unsuccessful treatment was the cause of drug withdrawal in only 5% of the patients, although an additional 25% stopped taking the drug for various reasons. Actuarial survival for the whole group, and subgroups with SVT and ventricular tachycardia/fibrillation were 66%, 74% and 52%, respectively, at 50 months. For the whole group, the actuarial probability of being alive and continuing with amiodarone therapy was only 19% at 50 months. Thus, although amiodarone was effective, few patients tolerated the drug on a long-term basis. Although amiodarone remains a valuable treatment for patients with ventricular tachycardia, its long-term effectiveness for patients with SVT is less certain.

Rapid suppression of complex ventricular arrhythmias with high-dose oral amiodarone

Although amiodarone is effective for the suppression of complex ventricular arrhythmias, a major problem with its use is the long delay between the initiation of therapy and the onset of effective suppression of arrhythmia. To test the hypothesis that rapid loading with oral amiodarone to a target serum concentration can overcome much of this delay, eight patients with refractory, sustained, hemodynamically compromising ventricular arrhythmias and 10 patients with potentially life-threatening ventricular arrhythmias were treated with a flexible, very high dose, oral loading protocol (800 to 2000 mg two to three times a day). Dosage was adjusted on the basis of amiodarone serum concentrations to maintain the trough serum concentrations between 2.0 and 3.0 micrograms/ml. Comparison of 24 hr Holter electrocardiograms obtained before and during therapy revealed statistically significant reductions in premature ventricular complexes (PVCs) and paired PVCs beginning the first day of therapy and a reduction in ventricular tachycardia (VT) beginning the second day. By day 2, four of eight patients with sustained VT and six of 10 patients with nonsustained VT showed no VT. Pulmonary arterial catheterization during the first 24 hr (mean amiodarone dose 3933 mg) revealed no significant hemodynamic alterations. Minor side effects were common (10 patients) but major side effects were rare (one patient). High-dose oral loading with amiodarone utilizing serum concentration guidelines is a safe and effective method of rapidly controlling life-threatening arrhythmias in selected patients.

Effects of congestive heart failure on the pharmacokinetics and pharmacodynamics of antiarrhythmic agents

Changes in the pharmacokinetics of antiarrhythmic agents should be expected in patients with congestive heart failure (CHF). The direction of the changes, however, is not always predictable. The volume of distribution is often decreased by as much as 40%, and loading doses should, therefore, be appropriately reduced. Drug clearance may also be diminished due to decreased blood flow to the liver and kidneys, as well as decreased hepatic drug-metabolizing activity. Infusion rates should similarly be lowered to avoid toxicity. However, decreases in both volume of distribution and clearance may result in little, if any, change in elimination half-life, despite higher plasma concentrations. On the other hand, the elimination half-life of antiarrhythmic agents that have a large volume of distribution and are highly cleared by the liver may be twice as long in patients with CHF compared with normal subjects. Thus, the total daily dose of drug should also be lower in these patients. In addition, the time necessary to reach steady state is longer, so that premature dose escalation may lead to excessive drug accumulation. In terms of their pharmacodynamic effects, all antiarrhythmic agents have the potential to manifest a degree of negative inotropy, which must be anticipated as a possible side effect in patients with CHF. Some of the newer agents, such as tocainide and encainide, appear to cause only minimal myocardial depression. Other potential complications of all antiarrhythmic therapy include proarrhythmia and possible drug interactions with digitalis and diuretics.

Amiodarone pulmonary toxicity. Chest radiography and CT in asymptomatic patients

Two asymptomatic patients from a group of 30 being treated with the antiarrhythmic drug amiodarone developed roentgenographic pulmonary and pleural reactions. Computed tomography in one patient with an uncommon radiographic pattern of fuzzy nodules showed the spatial distribution of the parenchymal changes, as well as unrecognized pleural thickening. The disease in these asymptomatic patients was presumably detected on the periodic chest roentgenogram at an early stage because the changes disappeared after withdrawal of the drug. Periodic chest radiographs are recommended during amiodarone therapy and CT may be useful in evaluation of patients with unusual chest radiographic findings.

Pneumonitis with pleural and pericardial effusion and neuropathy during amiodarone therapy

A patient with sinuatrial disease and implanted pacemaker was treated with amiodarone (maximum dose 1000 mg, maintenance dose 800 mg daily) for 10 months, for control of supraventricular tachyarrhythmias. He developed pneumonitis, pleural and pericardial effusions, and a predominantly proximal motor neuropathy. Immediate but gradual improvement followed withdrawal of amiodarone and treatment with prednisolone. Review of this and previously reported cases indicates the need for early diagnosis of amiodarone pneumonitis, immediate withdrawal of amiodarone, and prompt but continued steroid therapy to ensure full recovery.

Amiodarone: correlation of serum concentration with suppression of complex ventricular ectopic activity

Although amiodarone has been used for the suppression of complex ventricular arrhythmias since the early 1970s, there is a paucity of information regarding the relation of serum concentration to arrhythmia suppression. To investigate this relation, 25 patients receiving chronic amiodarone therapy for complex ventricular arrhythmias were retrospectively studied. At each visit a blood sample for determination of trough serum amiodarone concentration and a 24-hour 2-channel ambulatory electrocardiogram (ECG) were obtained. Dosage was adjusted, based on the ambulatory ECG, to maintain arrhythmia suppression at the lowest possible amiodarone dose and, hence, because of the extremely long half-life of amiodarone, patients were rarely in a true steady state. Over 17 months, 218 ambulatory ECGs with corresponding serum samples were analyzed. Negative correlations between serum amiodarone concentration and the frequencies of premature ventricular complexes (PVCs), paired PVCs and ventricular tachycardia were found (p less than 0.005, p less than 0.005 and p less than 0.05, respectively). No correlations existed between amiodarone dose and these arrhythmias. Trough serum amiodarone concentrations greater than 2.0 micrograms/ml were associated with significant reductions in the frequencies of PVCs (p less than 0.01) and paired PVCs (p less than 0.02) when compared with serum concentrations below this level. A reduction in ventricular tachycardia was seen with serum concentrations greater than 1.5 micrograms/ml (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Amiodarone: intravenous loading for rapid suppression of complex ventricular arrhythmias

A major disadvantage of conventional amiodarone therapy is the long delay between initiation of therapy and arrhythmia suppression. In this study, the hypothesis was tested that complex ventricular arrhythmias would be suppressed rapidly by an intravenous amiodarone infusion designed to achieve and maintain a therapeutic serum concentration. Eleven patients were studied. Each underwent a single intravenous dose kinetic study, followed by a two stage infusion of amiodarone that achieved and maintained a serum concentration of 2 to 3 micrograms/ml. In seven patients, arrhythmias during hours 24 to 48 after the infusion were compared with arrhythmias without therapy. Amiodarone therapy reduced episodes of ventricular tachycardia by 85% (p less than 0.01), paired premature ventricular complexes by 74% (p less than 0.01) and premature ventricular complexes by 60% (p less than 0.05). Four patients could not tolerate a control period without therapy because of symptomatic arrhythmias. In three patients, symptomatic arrhythmias were abolished during the 24 hour evaluation period. Two of 11 patients, both with severe left ventricular dysfunction, developed significant hypotension during the loading phase of the infusion. It is concluded that the achievement and maintenance of a therapeutic serum concentration of intravenous amiodarone are effective in the rapid suppression of life-threatening ventricular arrhythmias. Caution should be employed when using large intravenous doses in patients with severely impaired left ventricular function.

Effect of amiodarone on serum quinidine and procainamide levels

Serum levels of quinidine or procainamide were measured in patients who had amiodarone added to their antiarrhythmic regimen. Dosages of quinidine or procainamide were held constant. Eleven of 11 patients had an increase in the serum quinidine level, and 11 of 12 other patients had an increase in the serum procainamide level. The dose requirement to maintain a stable plasma level of quinidine or procainamide decreased by 37% and 20%, respectively. Clinical toxicity occasionally occurred with the increase in serum levels of quinidine and procainamide, and the dose of these drugs should be decreased when amiodarone is administered concurrently.

Amiodarone: electrophysiologic actions, pharmacokinetics and clinical effects

Interest in amiodarone has increased because of its remarkable efficacy as an antiarrhythmic agent. The purpose of this report is to review what is known about the electrophysiologic actions, hemodynamic effects, pharmacokinetics, alterations of thyroid function, response to treatment of supraventricular and ventricular tachyarrhythmias and adverse effects of amiodarone. Understanding the actions of amiodarone and its metabolism will provide more intelligent use of the drug and minimize the development of side effects. The mechanism by which amiodarone suppresses cardiac arrhythmias is not known and may relate to prolongation of refractoriness in all cardiac tissues, suppression of automaticity in some fibers, minimal slowing of conduction in fast channel-dependent tissue, or to interactions with the autonomic nervous system, alterations in thyroid metabolism or other factors. Amiodarone exerts definite but fairly minor negative inotropic effects that may be offset by its vasodilator actions. Amiodarone has a reduced clearance rate, large volume of distribution, low bioavailability and a long half-life that may last 2 months in patients receiving short-term therapy. Therapeutic serum concentrations range between 1.0 and 3.5 micrograms/ml. The drug suppresses recurrences of cardiac tachyarrhythmias in a high percent of patients, in the range of 80% or more for most supraventricular tachycardias and in about 66% of patients with ventricular tachyarrhythmias, sometimes requiring addition of a second antiarrhythmic agent. Side effects, particularly when high doses are used, may limit amiodarone's usefulness and include skin, corneal, thyroid, pulmonary, neurologic, gastrointestinal and hepatic dysfunction. Aggravation of cardiac arrhythmias occurs but serious arrhythmias are caused in less than 5% of patients. Amiodarone affects the metabolism of many other drugs and care must be used to reduce doses of agents combined with amiodarone.

Toxic and therapeutic effects of amiodarone in the treatment of cardiac arrhythmias

Amiodarone was used to treat cardiac arrhythmias that had been refractory to conventional medical therapy. The first 70 consecutive patients treated with amiodarone in this study had at least 6 months of follow-up (range 6 to 24, mean 11) and form the basis for this report. Sixty-six patients were treated for ventricular arrhythmias and four for supraventricular tachycardias. Amiodarone therapy consisted of a loading dose of 600 mg orally twice a day for 7 days, and 600 mg daily thereafter. Doses were reduced only if side effects occurred. Because of frequent side effects, the dose was reduced from 572 +/- 283 mg per day (mean +/- standard deviation) at 45 days to 372 +/- 174 mg per day at 6 months. With a mean follow-up of 11 months in the 54 patients who continued to take amiodarone, only 4 patients had ventricular fibrillation. Three additional patients experienced recurrent sustained ventricular tachycardia in long-term follow-up. All 70 patients had extensive clinical and laboratory evaluation in follow-up. Side effects were common, occurring in 93% of patients. Thirteen patients (19%) had to discontinue the medication because of severe side effects. Fifty-six patients had gastrointestinal side effects, most commonly constipation. All patients but 1 eventually developed corneal microdeposits, and 43 patients were symptomatic. Cardiovascular side effects were uncommon. Symptomatic pulmonary side effects occurred in seven patients, with unequivocal pulmonary toxicity occurring in five. Neurologic side effects, most commonly tremor and ataxia, occurred in 52 patients. Thyroid dysfunction occurred in 3 patients, and 32 patients had cutaneous abnormalities. Miscellaneous other side effects occurred in 32 patients. Amiodarone appears to be useful in the management of refractory arrhythmias. Because virtually all patients develop side effects when given a maintenance daily dose of 600 mg, lower maintenance doses should be used. It is unknown if the more severe side effects are dose-related. Amiodarone is difficult to administer because of its narrow toxic-therapeutic range and prolonged loading phase. More importantly, the first sign of antiarrhythmic failure may be manifest as sudden cardiac death.

Hemodynamic effects of intravenous administration of amiodarone in congestive heart failure from chronic Chagas' disease

Fourteen patients with congestive heart failure due to chronic Chagas' disease had hemodynamic studies before and 20, 40 and 60 minutes and 24 hours after intravenous amiodarone. Amiodarone was given initially as a bolus (5 mg/kg); after 1 hour a continuous infusion was maintained for 24 hours (total dose 900 to 1,050 mg). During the first hour of observation, heart rate and cardiac index decreased and mean right atrial, left ventricular end-diastolic pressures and pulmonary and systemic vascular resistances increased. Except for heart rate and mean right atrial pressure, all hemodynamic variables returned to control values at 24 hours. Thus, myocardial depression occurred with a dose of 5 mg/kg within the first hour of intravenous administration. Amiodarone must be cautiously administered by bolus, especially in patients with cardiac failure.

Amiodarone: individualizing dosage with serum concentrations

The purpose of the present report is to review the available pharmacokinetic information on amiodarone with an emphasis on our own experience in monitoring serum amiodarone concentrations. We have found that 400 mg should be the maximal maintenance dose; if that treatment fails, careful addition of other antiarrhythmic agents is preferable over an increase in amiodarone dosage. Serum concentrations below 2.5 mg/L will significantly improve amiodarone's benefit-to-risk ratio.

Amiodarone pulmonary toxicity

Of the side effects that complicate amiodarone therapy, pulmonary fibrosis is potentially the most serious. Therefore, the development of techniques to predict the onset of this troublesome reaction would be of great practical value. Reports of 39 patients who developed pulmonary toxicity with amiodarone were evaluated for clues to precipitating factors and information on the response to corticosteroid treatment. The majority of patients were being given maintenance doses greater than 400 mg/day. Patients appeared to improve after withdrawal of amiodarone, both with and without corticosteroid treatment. In addition, a case report is presented of a patient who developed pulmonary changes that disappeared when amiodarone was withdrawn and did not recur when amiodarone was reinstituted. Data from sequential pulmonary function tests and cumulative amiodarone dosage in 35 patients were also examined to determine their value in predicting pulmonary complications. Pulmonary function tests did not appear to be useful in predicting the likelihood of an individual patient's developing pulmonary complications. Although none of the available information identifies the mechanism mediating amiodarone pulmonary toxicity, the frequency of the complication probably can be reduced by timely reductions in maintenance dosage.

Evaluation of amiodarone therapy in the treatment of drug-resistant cardiac arrhythmias: long-term follow-up

The clinical efficacy of amiodarone in the management of complex cardiac arrhythmias refractory to therapy with two or more conventional or other investigational antiarrhythmic agents was determined by long-term follow-up in patients who had received the drug for at least 3 months. A total of 181 patients, classified into four groups (group 1, supraventricular arrhythmias, n = 42; group 2, frequent ventricular premature complexes, n = 46; group 3, nonsustained ventricular tachycardia, n = 16; and group 4, sustained ventricular tachycardia, n = 77) received a daily maintenance dose of 200 to 800 mg amiodarone for up to 30 months. There was a total of 26 deaths (14%). Ten of these were probably attributable to arrhythmia, although all patients had either good or excellent response to therapy over a mean follow-up of 14.9 months prior to death. The drug had to be permanently discontinued because of side effects in only three patients, and in the majority of patients with side effects, symptoms could be alleviated with adjustment of dosage, thyroid replacement therapy, or temporary cessation of therapy. We conclude that amiodarone is highly effective in high-risk patients with complex refractory cardiac arrhythmias, and that close monitoring and prompt recognition of side effects and appropriate adjustment of dosage or institution of supplemental or replacement therapy (in less than 5% of patients) will allow continuation of amiodarone. The benefit of suppression of symptomatic arrhythmias and the potential of prevention of sudden death clearly outweigh the modest incidence of severe side effects.

Amiodarone therapy for life threatening or refractory cardiac arrhythmias

Amiodarone was used in 40 patients with life-threatening or refractory tachyarrhythmias. Eighteen patients had recurrent ventricular tachycardia of whom 13 had suffered a cardiac arrest. Control has been excellent or good in 17 of these 18 patients during an average follow-up period of 10 months. A further 22 patients had supraventricular arrhythmias, including three with Wolff-Parkinson-White syndrome and paroxysmal atrial fibrillation. In 20 of these control has been excellent or good. The mean daily maintenance dose of amiodarone was 300 mg for patients with ventricular tachyarrhythmias and 200 mg for those with supraventricular tachyarrhythmias. Side-effects were common and included corneal microdeposits, skin rash and discolouration, alteration in thyroid function, and symptomatic bradycardia. Serious adverse effects were uncommon however and necessitated discontinuation of the drug in only two patients. Amiodarone did not appear to precipitate or exacerbate cardiac failure in any patient although many had severe left ventricular dysfunction. We conclude that amiodarone is effective in the therapy of life-threatening or refractory cardiac arrhythmias.

Acute overdosage of amiodarone in a suicide attempt

Clinical and biochemical variables and blood levels of amiodarone and its metabolite are reported after acute self-intoxication in a young woman. Despite the huge amount of drug ingested no clinical side effects were documented over the monitored period of 3 months.