Amiodarone and pulmonary fibrosis

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 pulmonary toxicity

The amount of literature on amiodarone pulmonary toxicity (APT) peaked in 1983-1984 with several hundred cases reported cumulatively, and declined thereafter. Since the mid-1990s, publications have increased, which suggests that APT remains a current problem in clinical practice. Amiodarone remains difficult to diagnose noninvasively, and although the outcome is good in the majority of patients, not all cases of APT can be controlled satisfactorily.

Amiodarone induced phospholipidosis. Biochemical, morphological and functional changes in the lungs of rats chronically treated with amiodarone

Amiodarone, an antiarrhythmic drug, causes pulmonary fibrosis in some patients during chronic treatment but the mechanism is unknown. We studied the effects of amiodarone on pulmonary biochemistry, morphology and function at doses of 25 and 50 mg/kg/12 hr given to rats by gavage for four weeks. Plasma and pulmonary phospholipids were significantly augmented, 13% and 88% respectively, in the group given amiodarone 50 mg/kg/12 hr compared to pair-fed controls. Typical phospholipidosis-like light and electron microscopic alterations were seen in the lung, their severity related to the extent of biochemical changes induced by amiodarone. Pulmonary function tests revealed mild but not significant changes in O2 and CO2 alveolar exchange efficiency and lung compliance (P-V curve) of treated animals in comparison to pair fed controls. Plasma average concentrations of amiodarone and its main metabolite, desethylamiodarone, after four weeks were 2.46 +/- 0.18 and 0.73 +/- 0.13 micrograms/ml, respectively, in the 50 mg/kg/12 hr group. In the same group amiodarone and desethylamiodarone concentrations in lung were 163 +/- 26 and 569 +/- 153 times higher than those in plasma. A highly significant correlation was found between amiodarone concentrations in plasma and lung and phospholipid content in the lung. A subgroup of animals received amiodarone 50 mg/kg/12 hr for 8 weeks. The pulmonary phospholipidosis-like lesions were similar to those observed after one month of treatment, no fibrosis was evident on light microscopic examination.

Amiodarone-induced ultrastructural changes in canine myocardial fibers

Chronic clinical toxicity with amiodarone, a unique antiarrhythmic drug, is associated with intracellular myelinoid inclusion bodies in skin, cornea, lung, liver and lymph nodes. The present study was designed to develop a canine animal model to study amiodarone concentration and onset of formation of myelinoid inclusion bodies in the cardiac tissue. Amiodarone was given intravenously in a single dose (40 mg/kg body weight) or multiple doses (40 mg/kg IV + 10 mg/kg IV X 7 days). Amiodarone concentration in the heart was high after a single dose but electron microscopic examination showed a normal ultrastructure. Numerous myelinoid inclusion bodies were found in the myofibrils of the left atria and right and left ventricles after only 7 days of amiodarone treatment. Myelinoid inclusion bodies were identified in several subcellular locations including intercalated disc but most were in close proximity of the mitochondria, sometimes touching and indenting the mitochondrial membrane. The antiarrhythmic effect of the schedule of intravenous amiodarone for 7 days used in this study was minimal, and this correlated with unexpectedly low myocardial levels of the drug and its metabolite. The results are consistent with our previous data of an antiarrhythmic effect with a single intravenous dose of 40 mg/kg body weight associated with high myocardial levels of amiodarone. We conclude that a single large dose of amiodarone with high tissue level may not cause myelinoid inclusion bodies, but they can be readily identified in all heart chambers after only 1 week of amiodarone treatment. This model would be useful to study amiodarone-induced ultrastructural changes in the heart.

Systematically applied chemicals that damage lung tissue

A large, and increasing number of drugs and chemicals have been found which are toxic to lung following systemic administration. These agents damage lung tissue specifically, or in addition to damage to other tissues. Mechanisms explaining the pulmonary damage produced by some lung toxins have been uncovered. These include concentration of the agent within lung, the absence of adequate pulmonary detoxication systems, and bioactivation to a toxic species within specific lung cells or at distant sites followed by transport to the lung. The basic biochemical lesions underlying lung damage, responses of individual lung cells and pulmonary repair processes to the toxic agent, and species and age differences in susceptibility to lung damage have not, however, been well defined for most lung toxins. This review describes the information available on pulmonary biochemical and pathological changes associated with some of these lung-toxic agents. In addition, mechanisms proposed to explain the lung damage are discussed. The agents covered include: paraquat, the thioureas, butylated hydroxytoluene, the trialkylphosphorothioates, various lung-toxic furans and antineoplastic agents, the pyrrolizidine alkaloids, metals and organometallic compounds, amphiphilic agents, hydrocarbons, oleic acid, 3-methylindole, and diabetogenic agents. Detailed reviews on the overall toxicity of many of these agents have been published elsewhere. This review concentrates on their pulmonary toxicity. Information is presented as an overview to illustrate both the extensive literature that is available and the important questions that remain to be answered about systemic chemicals that damage lung tissue.

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 pneumonitis: three further cases with a review of published reports

Three further patients are presented who developed evidence of a parenchymal pulmonary disturbance in the course of treatment with amiodarone. In one case the progress of the condition was rapid and ended fatally. Histological examination of the lungs showed evidence of diffuse alveolar damage. The concentration of amiodarone was from four to seven times higher in the lungs than in other organs studied. The concentration of the metabolite desethylamiodarone in the lungs was even higher in relation to other organs studied. The remaining two patients showed a more insidious onset and improvement after withdrawal of amiodarone and treatment with corticosteroids. Gallium 67 scintigraphy appeared to be a sensitive indicator of this adverse effect. Review of published reports revealed 35 cases of amiodarone pneumonitis, including the cases reported in this study. In 11 instances the dose of amiodarone was 400 mg or less. The onset was either insidious or rapidly progressive. Exertional dyspnoea was always present and a nonproductive cough, hypoxaemia, a raised erythrocyte sedimentation rate and diminished carbon monoxide diffusing capacity (transfer factor) were usually noted. Chest radiographs showed either a reticular pattern or diffuse patchy alveolar infiltrates. Discontinuation of amiodarone and an institution of corticosteroid treatment was usually followed by improvement or resolution.