Amiodarone pneumonitis: no safe dose

Amiodarone lung: under recognised but not forgotten

Amiodarone is a common medication used widely in clinical practice. It is a triiodinated antiarrhythmic associated with a variety of adverse effects both pulmonary and extrapulmonary, the most serious being amiodarone-induced pulmonary toxicity (AIPT) or amiodarone lung. This can present with a variety of clinical syndromes ranging from subacute symptoms to an indolent and a progressive course thus mimicking an alternative diagnosis. We report a case of amiodarone lung in a female who presented with an acute fulminant progressive pneumonitis despite being on very low dose (100 mg once daily) that proved fatal. Diagnosis was made on postmortem examination due to a diagnostic conundrum. Despite the steady decrease of AIPT with reduced dose, it is vital for the treating clinicians to monitor regularly for adverse effects and review the need for long-term use to prevent complications.

A nontrivial differential diagnosis in COVID-19 pandemic: a case report and literary review of amiodarone-induced interstitial pneumonia

Amiodarone is a drug commonly used to treat and prevent cardiac arrhythmias, but it is often associated with several adverse effects, the most serious of which is pulmonary toxicity. A 79-year-old man presented with respiratory failure due to interstitial pneumonia during the COVID-19 pandemic. The viral etiology was nevertheless excluded by repeated nasopharyngeal swabs and serological tests and the final diagnosis was amiodarone-induced organizing pneumonia. The clinical and computed tomography findings improved after amiodarone interruption and steroid therapy. Even during a pandemic, differential diagnosis should always be considered and pulmonary toxicity has to be taken into account in any patient taking amiodarone and who has new respiratory symptoms.

Amiodarone-induced pulmonary toxicity--a fatal case report and literature review

Amiodarone is a widely used and very potent antiarrhythmic substance. Among its adverse effects, pulmonary toxicity is the most dangerous without a causal treatment option. Due to a very long half-life, accumulation can only be prevented by strict adherence to certain dosage patterns. In this review, we outline different safe and proven dosing schemes of amiodarone and compare the incidence and description of pulmonary toxicity. Reason for this is a case of fatal pulmonary toxicity due to a subacute iatrogenic overdosing of amiodarone in a 74-year-old male patient with known severe coronary artery disease, congestive heart failure and ectopic atrial tachycardia with reduced function of kidneys and liver but without preexisting lung disease. Within 30 days, the patient received 32.2 g of amiodarone instead of 15.6 g as planned. Despite early corticosteroid treatment after fast exclusion of all other differential diagnoses, the patient died another month later in our intensive care unit from respiratory failure due to bipulmonal pneumonitis.

Lymphoid hyperplasia and eosinophilic pneumonia as histologic manifestations of amiodarone-induced lung toxicity

Amiodarone use is often limited by pulmonary toxicity. Amiodarone lung disease (ALD) classically manifests as organizing pneumonia with intra-alveolar foamy macrophages, but other patterns may also occur. Here we report 2 previously unreported patterns of ALD: lymphoid hyperplasia (LH) and eosinophilic pneumonia (EP). We identified patients with LH or EP as a prominent feature among 75 cases of probable ALD from the authors' teaching files collected from 1997 to 2010. Clinical history and lung wedge biopsies were reviewed. Twelve patients (7 men) met inclusion criteria (median age, 71 y). The exact amiodarone dose was known in all cases (median, 200 mg/d). Treatment duration was known in 10 cases and ranged from 1 to 12 years. Thoracic imaging showed diffuse infiltrates causing concern for a diagnosis of ALD. Histologic review revealed intra-alveolar foamy macrophages in all cases. Eight cases prominently displayed patterns of LH, including diffuse LH (7), follicular bronchiolitis (5), lymphoid interstitial pneumonia (2), and lymphocytic perivascular cuffing (2). Two showed features of acute EP, including diffuse alveolar damage with abundant eosinophils. Two showed features of chronic EP, including interstitial pneumonia with abundant eosinophils, patchy organization, and fibrinous exudates with macrophages and eosinophils. One chronic EP case also showed focal LH. Additional features included intra-alveolar giant cells (6), pleuritis (3), small poorly formed granulomas (3), and thrombi (2). LH and EP are previously unrecognized histopathologic manifestations of ALD, and amiodarone exposure should be included in their differential diagnosis.

Examining the safety of amiodarone

INTRODUCTION

Amiodarone is the most widely used antiarrhythmic agent, with demonstrated effectiveness against all the spectrum of cardiac tachyarrhythmias. The risk of adverse effects acts as a limiting factor to its utilization especially in the long term. This article systematically reviews the published evidence on amiodarone versus placebo to examine its safety as an antiarrhythmic drug.

AREAS COVERED

Authors collected data on adverse effects reported in 49 randomized placebo-controlled trials with amiodarone. Adverse effects were classified according to the organ/system involved. Pooled estimates of the number needed to treat (NNT) and to harm (NNH) versus placebo were calculated.

EXPERT OPINION

Amiodarone is effective for both the acute conversion of atrial fibrillation (AF) (11 trials, NNT = 4 at 24 h; p = 0.003) and the prevention of postoperative AF (18 trials, NNT = 8; p < 0.001), although with an increased risk of bradycardia, hypotension, nausea or phlebitis (pooled NNH = 4; p < 0.001). Amiodarone administration for the maintenance of sinus rhythm has a favorable net clinical benefit (pooled NNT = 3; p < 0.001 versus pooled NNH for either thyroid toxicity, gastrointestinal discomfort, skin toxicity or eye toxicity = 11; p < 0.001). Treatment with amiodarone for the prophylaxis of sudden cardiac death has less favorable net clinical benefit (15 trials, NNT = 38; p < 0.001 versus NNH for either thyroid toxicity, hepatic toxicity, pulmonary toxicity or bradycardia = 14; p < 0.001). Amiodarone treatment in this setting should be used in only selected cases.

Managing atrial fibrillation in the elderly: critical appraisal of dronedarone

Atrial fibrillation is the most commonly seen arrhythmia in the geriatric population and is associated with increased cardiovascular morbidity and mortality. Treatment of the elderly with atrial fibrillation remains challenging for physicians, because this unique subpopulation is characterized by multiple comorbidities requiring chronic use of numerous medications, which can potentially lead to severe drug interactions. Furthermore, age-related changes in the cardiovascular system as well as other physiological changes result in altered drug pharmacokinetics. Dronedarone is a new drug recently approved for the treatment of arrhythmias, such as atrial fibrillation and/or atrial flutter. Dronedarone is a benzofuran amiodarone analog which lacks the iodine moiety and contains a methane sulfonyl group that decreases its lipophilicity. These differences in chemical structure are responsible for making dronedarone less toxic than amiodarone which, in turn, results in fewer side effects. Adverse events for dronedarone include gastrointestinal side effects and rash. No dosage adjustments are required for patients with renal impairment. However, the use of dronedarone is contraindicated in the presence of severe hepatic dysfunction.

Amiodarone pulmonary toxicity

Amiodarone is an antiarrhythmic agent commonly used to treat supraventricular and ventricular arrhythmias. This drug is an iodinecontaining compound that tends to accumulate in several organs, including the lungs. It has been associated with a variety of adverse events. Of these events, the most serious is amiodarone pulmonary toxicity. Although the incidence of this complication has decreased with the use of lower doses of amiodarone, it can occur with any dose. Because amiodarone is widely used, all clinicians should be vigilant of this possibility. Pulmonary toxicity usually manifests as an acute or subacute pneumonitis, typically with diffuse infiltrates on chest x-ray and high-resolution computed tomography. Other, more localized, forms of pulmonary toxicity may occur, including pleural disease, migratory infiltrates, and single or multiple nodules. With early detection, the prognosis is good. Most patients diagnosed promptly respond well to the withdrawal of amiodarone and the administration of corticosteroids, which are usually given for four to 12 months. It is important that physicians be familiar with amiodarone treatment guidelines and follow published recommendations for the monitoring of pulmonary as well as extrapulmonary adverse effects.

Amiodarone-induced pulmonary toxicity

AIMS

A number of factors have been hypothesized to increase the risk of amiodarone-induced pulmonary toxicity (AIPT). This study aimed to confirm these risk factors and determine whether a cohort of tertiary hospital patients diagnosed with AIPT demonstrated comparable characteristics.

METHODS

Phase I of this study involved compilation of a database of adverse reactions to amiodarone reported to the Australian and US drug agencies, and identification of risk factors for AIPT using logistic regression analysis. In Phase II, AIPT cases were identified via a retrospective review of medical records of patients discharged from Fremantle Hospital and Health Service, Western Australia (FHHS) between 2000 and 2005 with diagnosed interstitial lung disease. Data were collected regarding these patients' risk factors for AIPT and compared with those previously identified in Phase I.

RESULTS

A total of 237 cases of AIPT were identified from agency data. Patients aged > 60 years and those on amiodarone for 6-12 months (odds ratio 18.28, 95% confidence interval 6.42, 52.04) were determined to be at the highest risk of AIPT. Australian data also suggested increased risk in patients who had received cumulative doses of 101-150 g. The seven AIPT cases identified among the FHHS patients were all at high risk of AIPT based on their age and duration of amiodarone therapy.

CONCLUSION

Contrary to previous findings, only patient age and the duration of amiodarone therapy were confirmed as significant risk factors for AIPT. Targeted monitoring of these patients may facilitate early identification and management of AIPT.

Pulmonary toxicity in patients receiving low-dose amiodarone

RATIONALE

Although there have been reports of pulmonary toxicity with low-dose amiodarone, it is generally believed that low-dose therapy is safe.

METHODS

The clinical data for eight patients identified from a retrospective chart review are presented.

RESULTS

All of the patients were receiving amiodarone, 200 mg/d, for an average of 2 years. The average age was 77 years (range, 65 to 89 years). Seven of the eight patients were male. Seven of the eight patients presented with dyspnea on exertion, and three of the eight patients presented with cough. All of the patients had a clinical diagnosis of amiodarone-induced pulmonary toxicity. Open-lung biopsies were obtained on two patients that were consistent with amiodarone-induced pulmonary toxicity. None of the patients were in congestive heart failure. Treatment involved cessation of amiodarone. In addition, three patients received corticosteroids. Five of the patients improved symptomatically with this conservative approach, and four patients improved radiographically. One patient died with progressive respiratory insufficiency (presumably from amiodarone pulmonary toxicity). One patient was unavailable for follow-up.

CONCLUSION

Amiodarone-induced pulmonary toxicity can occur at a daily dose of 200 mg. Clinicians must remain alert to this possibility even with this low-dose therapy.

Diagnostic accuracy of KL-6 as a marker of amiodarone-induced pulmonary toxicity

The diagnostic accuracy of KL-6 as an indicator of amiodarone-induced pulmonary toxicity was studied in 14 men (mean age = 62 +/- 12, range 33-76 years) treated with amiodarone. The indications for amiodarone were sustained ventricular tachycardia in 13 patients and atrial fibrillation in 1 patient with refractory heart failure. The KL-6 cut-off level was set at 520 U/mL. Group A consisted of two patients with amiodarone-induced pulmonary toxicity, group B of five patients with other pulmonary disorders, and group C of seven patients without pulmonary disease. KL-6 levels, percent diffusing capacity for carbon monoxide (%DLCO), and other laboratory markers were compared among these three groups. KL-6 levels were significantly higher in group A than in group B and C (2550 +/- 36, 252 +/- 99, 198 +/- 82 U/mL, respectively; P < 0.0001). KL-6 levels in group B were below the cutoff value. %DLCO, C-reactive protein (CRP), and lactic dehydrogenase (LDH) were abnormal in group A. The abnormal rates of CRP and LDH in group B were 80% and 40%, respectively. Of the seven patients with pulmonary disease, three patients (43%) could not undergo %DLCO testing because of poor physical condition. In one patient with amiodarone-induced pulmonary toxicity, the KL-6 level increased from 695 to 2,100 U/mL at a time of progression of interstitial changes. KL-6 may be a useful marker of amiodarone-induced pulmonary toxicity.

Clinical organ toxicity of antiarrhythmic compounds: ocular and pulmonary manifestations

The history of antiarrhythmic therapy reveals these agents to be associated with a high incidence of toxicity. Although several agents have ocular effects, amiodarone is the most widely recognized for producing adverse effects in the eyes. Corneal microdeposits are almost ubiquitous in patients being treated with amiodarone. However, they are, for the most part, benign and produce no changes in visual acuity. Lack of microdeposits should prompt the physician to investigate whether there is a problem with drug absorption or adherence to therapy. Other effects on the eye have been reported including optic neuropathy, but no causal link has been proved with amiodarone. The population of patients treated with amiodarone often have ischemic disease and/or diabetes, which affect retinal and optic nerve health. Many antiarrhythmic agents also affect lung function. The frequent association of procainamide with a lupus-like syndrome, where half the cases develop pleural-pericardial involvement, may require discontinuation of that drug. Although beta blockers and to a lesser degree, calcium antagonists, may cause bronchospasm in some patients, this is not usually a major clinical problem. Again, it is amiodarone that has the most widespread reputation for causing pulmonary toxicity. Although infrequent (< 1% incidence), it generates the most fear as it is sometimes fatal. Because of the lack of a diagnostic "gold standard," it is often overdiagnosed, placing patients at risk from overlooked congestive heart failure and infections and from recurrent arrhythmias after drug withdrawal. Patients with pre-existing pulmonary disease appear to be more at risk. Common features include indolent onset of cough, malaise and fever associated with patchy peripheral infiltrates, and severely decreased diffusion capacity. Several cases of pulmonary toxicity have had inordinately high serum desethylamiodarone to amiodarone ratios. Most cases recover with cessation of amiodarone therapy. Steroids are commonly used, but are of unproved efficacy. In terms of its toxicity, amiodarone remains the most feared of the antiarrhythmic agents. In the future, a better understanding of its pharmacokinetics, mechanisms of toxicity, and optimal dosing regimens should provide a possibility of better strategies for avoidance, early diagnosis, and more directed therapy of toxicities associated with amiodarone.

Adverse effects of amiodarone

Amiodarone was introduced 30 years ago as an antianginal agent and subsequently has been used as an antiarrhythmic agent. This drug was initially used for patients with malignant ventricular arrhythmias; however, currently it is being used broadly for rate and rhythm control in patients with atrial fibrillation. At first, amiodarone was primarily used by cardiologists and today it is used throughout the medical profession. Amiodarone therapy can potentially result in a wide range of adverse effects. The majority of these adverse effects are dose related and reversible. The following is a review of the adverse effects and drug interactions of amiodarone along with recommendations for identification and management of these adverse effects.