What are the effects of Amiodarone (antiarrhythmic medication) induced pneumonitis?

From the Guidelines

Amiodarone-induced pneumonitis is a serious potential adverse effect of amiodarone therapy, and if suspected, the drug should be discontinued immediately and supportive care provided, with corticosteroids considered in some cases. The most common clinical presentation is subacute cough and progressive dyspnea, with associated patchy interstitial infiltrates on chest radiographs 1. The frequency of pulmonary toxicity in amiodarone therapy has been reported to be 2 to 17 percent in early studies, but more recent studies have shown a lower incidence in patients receiving dosages of 300 mg per day or less 1.

Some key points to consider in the management of amiodarone-induced pneumonitis include:

• Routine screening for adult respiratory distress syndrome is of limited value, because pulmonary toxicity can develop rapidly with no antecedent abnormalities on chest radiographs or pulmonary function tests 1
• Any report from the patient of worsening dyspnea or cough should elicit a prompt assessment for pulmonary toxicity, and congestive heart failure should be ruled out early in the evaluation 1
• High-resolution computed tomographic scanning can be helpful in making a diagnosis 1
• The primary treatment for pulmonary toxicity is withdrawal of amiodarone and provision of supportive care and, in some cases, corticosteroids 1

It is essential to note that the toxicity is reversible in most instances, but recovery may take months even after drug discontinuation due to amiodarone's prolonged tissue retention 1. Alternative antiarrhythmic medications should be considered for ongoing rhythm control. Patients require close monitoring with baseline and periodic pulmonary function tests, chest X-rays, and oxygen saturation measurements.

From the FDA Drug Label

Pulmonary Disorders Early-onset Pulmonary Toxicity There have been postmarketing reports of acute-onset (days to weeks) pulmonary injury in patients treated with intravenous amiodarone. Findings have included pulmonary infiltrates and/or mass on X-ray, bronchospasm, wheezing, fever, dyspnea, cough, hemoptysis, and hypoxia. Some cases have progressed to respiratory failure and/or death ARDS Two percent (2%) of patients were reported to have adult respiratory distress syndrome (ARDS) during clinical studies involving 48 hours of therapy. ARDS is a disorder characterized by bilateral, diffuse pulmonary infiltrates with pulmonary edema and varying degrees of respiratory insufficiency The clinical and radiographic picture can arise after a variety of lung injuries, such as those resulting from trauma, shock, prolonged cardiopulmonary resuscitation, and aspiration pneumonia, conditions present in many of the patients enrolled in the clinical studies. There have been postmarketing reports of ARDS in intravenous amiodarone patients Intravenous amiodarone may play a role in causing or exacerbating pulmonary disorders in those patients. Postoperatively, occurrences of ARDS have been reported in patients receiving oral amiodarone therapy who have undergone either cardiac or noncardiac surgery. Although patients usually respond well to vigorous respiratory therapy, in rare instances the outcome has been fatal Until further studies have been performed, it is recommended that FiO 2 and the determinants of oxygen delivery to the tissues (e.g., SaO 2, PaO 2) be closely monitored in patients on amiodarone. Pulmonary Fibrosis Only 1 of more than 1000 patients treated with amiodarone HCl injection in clinical studies developed pulmonary fibrosis. In that patient, the condition was diagnosed 3 months after treatment with amiodarone HCl injection, during which time she received oral amiodarone Pulmonary toxicity is a well-recognized complication of long-term amiodarone use

Amiodarone-induced pneumonitis is a potential complication of amiodarone therapy. The drug label reports postmarketing cases of acute-onset pulmonary injury, including pulmonary infiltrates, bronchospasm, and respiratory failure.

• Key findings include pulmonary infiltrates and/or mass on X-ray, bronchospasm, wheezing, fever, dyspnea, cough, hemoptysis, and hypoxia.
• ARDS has been reported in 2% of patients during clinical studies, and intravenous amiodarone may play a role in causing or exacerbating pulmonary disorders.
• Pulmonary fibrosis is a rare complication, with only 1 case reported in over 1000 patients treated with amiodarone HCl injection. The FDA drug label recommends close monitoring of FiO2 and oxygen delivery to the tissues in patients on amiodarone 2.

From the Research

Amiodarone-Induced Pneumonitis

• Amiodarone-induced pneumonitis is a rare but serious complication of amiodarone therapy, with an estimated incidence of 1% to 5% 3, 4.
• The condition can present as progressive respiratory failure, with nonspecific respiratory symptoms such as dyspnea, cough, and occasionally fever 3, 5.
• Risk factors for amiodarone-induced pneumonitis include old age, high daily doses, and long-lasting therapy 3, 5.
• Diagnosis requires a combination of clinical, radiological, and histological data, with computed tomography (CT) often revealing ground-glass opacities and interstitial thickening 3.

Clinical Presentation and Diagnosis

• Patients with amiodarone-induced pneumonitis typically present with dyspnea, cough, and occasionally fever 3, 5.
• Chest radiographs and computed tomography (CT) scans can show diffuse interstitial pneumonitis patterns and ground-glass opacities 3, 5.
• Pulmonary function tests, including diffusion capacity for carbon monoxide, can be useful in diagnosing and monitoring amiodarone-induced pneumonitis 4.

Treatment and Management

• Management of amiodarone-induced pneumonitis focuses on discontinuing amiodarone and initiating corticosteroid therapy 3, 4, 6.
• Early withdrawal of amiodarone is crucial for symptom resolution and preventing progression to severe lung injury or irreversible fibrosis 3.
• Corticosteroid therapy can be life-saving for severe cases and can lead to complete resolution of symptoms and full recovery of lung function 6.

Prevention and Monitoring

• Patients who should benefit from amiodarone should be carefully selected and the lowest effective dosage of amiodarone should be taken 4.
• Pulmonary evaluation with chest X-ray and pulmonary function testing is recommended when amiodarone is started, and regular monitoring can help detect amiodarone-induced pneumonitis early 4.
• A documented decline in the diffusing capacity of greater than 20% is useful in suggesting the need for closer monitoring or for further diagnostic testing 4.