Amiodarone: Review of Pulmonary Effects and Toxicity

Authors, Journal, Affiliations, Type, DOI

• Authors: Spyros A. Papiris, Christina Triantafillidou, Likurgos Kolilekas, Despoina Markoulaki, Effrosyni D. Manali
• Journal: Drug Safety
• Year / Volume: 2010, Vol. 33, No. 7, pp. 539–558
• Affiliations: 2nd Pulmonary Department, 'Attikon' University Hospital, National and Kapodistrian University of Athens, Athens Medical School
• Type: Comprehensive narrative review (no conflicts of interest declared; no funding)
• DOI: 10.2165/11532320-000000000-00000

Overview

This 2010 Drug Safety review updates the amiodarone pulmonary toxicity (APT) framework with three key refinements beyond earlier literature. It introduces a clinically important two-tier distinction — "amiodarone effect" (asymptomatic lipoid pneumonia) vs "amiodarone toxicity" (distinct inflammatory patterns) — and a three-mechanism pathophysiology (cytotoxic, immune-mediated, angiotensin enzyme system). New quantitative epidemiological benchmarks are provided: cumulative incidence 4.2%/7.8%/10.6% at 1/3/5 years; 3-fold APT risk per 10-year age increment over 60; CT density >70 HU suggestive but absent in 27–55% of cases; KL-6 sensitivity only 25%; pre-existing lung disease does not increase pulmonary mortality (AFFIRM data); and ACE inhibitors/ARBs may be protective.

Keywords

Amiodarone, amiodarone pulmonary toxicity, lipoid pneumonia, drug-induced lung disease, organizing pneumonia, ARDS, diffuse alveolar haemorrhage

Key Takeaways

Introduction and Historical Perspective

• Amiodarone-related adverse pulmonary effects may develop as early as day 2 of treatment to several years after initiation
• Pulmonary complications are one of the leading reasons for drug discontinuation
• Fatal complications include ARDS, pulmonary fibrosis, cirrhosis, and bradycardia leading to cardiac arrest
• No drugs that prevent APT development have been described

Epidemiology and Risk Factors

• APT occurs in approximately 5% of treated patients overall (range 4.2–17% depending on definition used)
• Cumulative incidence by duration: 4.2% at 1 year → 7.8% at 3 years → 10.6% at 5 years
• Age: Most important risk factor; 3-fold increase per 10 years of age over 60; DLCO decline accelerated in elderly
• Dose relationship:
  • Maintenance doses >500 mg/day more toxic than <300 mg/day; APT occurs at 200 mg/day
  • Cumulative dose >10 g is an independent risk factor; risk persists up to 150 g cumulative
  • High DEAm plasma levels during maintenance — independent risk factor
• Risk factors for acute APT: cardiothoracic surgery, high FiO₂, pulmonary angiography, iodinated contrast media, sudden corticosteroid withdrawal
• Pre-existing lung disease (AFFIRM study data):
  • Pre-existing pulmonary disease associated with higher rate of diagnosed APT
  • Does NOT increase pulmonary death or all-cause mortality
  • Cautious amiodarone use acceptable even in elderly AF patients with pre-existing lung disease
  • Pretreatment DLCO is NOT an independent risk factor for APT if DLCO >45%
• ACE inhibitors / ARBs potentially protective: Two retrospective studies concluded angiotensin II (increased in chronic HF) enhances amiodarone-induced apoptosis of alveolar epithelial cells; patients on ACE inhibitors or ARBs had lower rates of APT. Not yet standard of care.
• Mortality: 9–10% for those who develop pneumonitis; 20–30% for those hospitalised; up to 50% for ARDS

Pharmacokinetics and Pathophysiology of Lung Damage

• Am and DEAm are amphiphilic — lipophilic moiety concentrates in high-lipid-content organs; cationic N-diethyl amino chain confers amphiphilic properties
• DEAm penetrates tissues ~5× more than parent molecule; acts as sustained-release reservoir; may unpredictably increase serum concentrations
• Lung parenchymal concentrations may exceed myocardial concentrations, especially with IV administration
• Three distinct mechanisms of toxicity:
  1. Direct cytotoxic effect: Amiodarone disrupts lysosomal membranes via protein C activation → release of toxic oxygen radicals → caspase pathway activation → apoptosis of lung epithelial cells; lysosomal phospholipase inhibition → phospholipid accumulation → lamellar inclusions in macrophage lysosomes
  2. Immune-mediated: Th1/Th2 lymphocyte imbalance; alveolar macrophages release TNF-α and TGF-β; genetically predisposed patients
  3. Angiotensin enzyme system activation: Amiodarone upregulates angiotensinogen mRNA/protein in AECs; angiotensin II (elevated in chronic HF) enhances amiodarone-induced AEC apoptosis; synergistic effect is a significant pathway for lung damage; mechanistically explains why ACE inhibitors/ARBs are potentially protective
• No dose or duration threshold has been established to avoid toxicity

Amiodarone Effect vs Amiodarone Toxicity — Key Distinction

• "Amiodarone effect" (lipoid pneumonia):
  • Ubiquitous — present in virtually all patients exposed chronically to amiodarone
  • Foamy macrophages occupy intra-alveolar and interstitial space → reduce effective gas exchange surface
  • Usually asymptomatic in patients with normal lung reserve
  • Detectable only by moderate and progressive reduction of DLCO
  • NOT a reason to stop amiodarone; represents drug effect, not toxicity
• "Amiodarone toxicity":
  • Distinct inflammatory lung reaction patterns — clinically significant
  • Includes: CEP, COP, AFOP, nodules/masses, NSIP-like, IPF-like, DIP, ALI/ARDS, DAH
  • Pleural/pericardial involvement in a minority

Clinical Picture — Acute Lung and Airway Disease

• May occur as early as day 2 of treatment; acute disease with cumulative doses as low as 1000–1500 mg IV
• Risk factors: pulmonary angiography, cardiothoracic surgery, high FiO₂, sudden corticosteroid withdrawal
• Patterns of acute toxicity:
  • ALI/ARDS: abrupt onset, rapid progression, high mortality; diffuse bilateral infiltrates; overlapping COP + DAD histology (AFOP type)
  • Diffuse alveolar haemorrhage (DAH): rare; haemoptysis; may relate to lymphocytic vasculitis of small capillaries; antiglomerular membrane antibodies reported once
  • Bronchospasm/asthma exacerbation/angioedema: anaphylactic-type reactions; fully reversible with treatment
• In ICU/post-surgical patients: alveolar or ground-glass opacities on CT + rapid respiratory deterioration may be the only clue
• Mechanism in cardiac surgery ARDS: high-FiO₂, ventilation lung damage, chest surgical damage, cardiopulmonary bypass systemic inflammatory response ('post-pump' syndrome), and iodine contrast → superoxide radicals + active iodide species

Clinical Picture — Subacute/Chronic Lung Disease

• Most common presentation: subacute illness — nonproductive cough, progressive exertional dyspnoea, low-grade fever, malaise, weight loss in a patient with heart disease on amiodarone
• Multiple distinct patterns:
  • Chronic eosinophilic pneumonia (CEP): rare; peripheral blood eosinophilia and/or BAL eosinophilia >25%; may present asymptomatically or with transient infiltrates
  • Chronic organising pneumonia (COP): indistinguishable from idiopathic; bilateral consolidation + ground-glass opacities, often peripheral; infiltrates may be migratory; clinical: SOB, cough, malaise, fever, pleuritic pain
  • Acute fibrinous and organising pneumonia (AFOP): variant that doesn't meet DAD/COP/CEP criteria; fulminant presentation with poor prognosis; intra-alveolar fibrin + organising pneumonia + type II cell hyperplasia
  • Nodules/masses ("amiodaronoma"): mass-like or nodular lesion; PET-positive — initial misdiagnosis as malignancy common; right upper lobe predominant; may have a halo or cavitate
  • NSIP-like: interstitial reticular opacities, traction bronchiectasis; more reversible than UIP
  • IPF-like: severe interstitial fibrosis, honeycombing at lung bases; difficult to distinguish from true IPF; amiodarone-related fibrosis appears milder and more slowly progressive
  • DIP (desquamative interstitial pneumonia): acute onset; diffuse AIP with respiratory failure may require mechanical ventilation

Clinical Picture — Pleural Disease

• Pleural effusion: rare, unilateral or bilateral, small-to-moderate volume; exudate (paucicellular, lymphocytic or neutrophilic predominance); isolated effusion without parenchymal disease is extremely rare
• Pleural thickening: common adjacent to peripheral parenchymal lesions
• Pericarditis associated with pleural effusion + pneumonitis described
• Drug-induced lupus: rare; pleuropericarditis + ANA + antihistone antibodies (serum marker); resolves after drug withdrawal

Laboratory Tests and Imaging

• Non-specific: elevated ESR, elevated LDH (may precede APT onset), leukocytosis, rarely eosinophilia
• BNP: elevated in LV failure; elevated BNP does NOT exclude APT (may co-exist)
• ANA + antihistone antibodies: drug-induced lupus subset
• KL-6 (MUC1 mucin, expressed on type II pneumocytes):
  • Sensitivity 25%, specificity 91%, PPV 22%, NPV 92% (at cut-off >500 U/mL)
  • High NPV useful to rule out APT; insufficient alone to stop amiodarone
  • Also elevated in other ILDs and sarcoidosis
• CT density:

  • 70 HU is suggestive of amiodarone-related lesions

  • However, absent in 27–55% of patients with APT — not a reliable ruling-out criterion
  • High attenuation in liver and spleen is indicative of amiodarone deposition (not necessarily toxicity)
  • Other conditions with high attenuation: metastatic pulmonary calcification, talcosis, iodinated oil embolism, silicoproteinosis, amyloidosis — interpret in clinical context
  • Gallium-67 scan: useful only to distinguish APT from pulmonary oedema and monitor progress; minimal modern utility
• CXR: annual unless symptomatic; CT more sensitive than plain film for bilateral disease

Pulmonary Function Testing

• DLCO ≥15% decrease: sensitivity 68–100%, specificity 69–95% for APT diagnosis
• Restrictive pattern and decreased DLCO in most patterns
• Decline significantly greater in patients with pre-existing COPD
• Stable DLCO in serial measurements excludes clinically significant APT
• Discontinuation should never rely solely on DLCO reduction

BAL and Lung Biopsy

• BAL indicates amiodarone exposure but has no specificity for toxicity
• BAL cellular pattern in APT (variable): lymphocytic 21%, neutrophilic 26%, mixed 33%, normal 20%; eosinophilia in almost half regardless of cellular profile
• CD4/CD8 ratio usually <1; increases after drug discontinuation
• No cellular BAL pattern predicts detrimental outcome or irreversible fibrosis
• Foamy macrophages = exposure marker; their absence makes APT less probable but does not exclude it
• Surgical lung biopsy: should generally be AVOIDED — high risk of ARDS post-procedure with rapid progression and high mortality; diagnosis is clinical exclusion
• Transbronchial biopsy when diagnosis urgently needed

Treatment Principles

• Stop amiodarone immediately when APT suspected; substitution with another AAD or ICD insertion in collaboration with cardiologist
• Corticosteroids: prednisolone 0.5–1 mg/kg; gradual taper; duration often 1 year (drug persists in lung tissue for up to 1 year after stopping)
• Corticosteroid taper caution: aggressive disease relapse described after reducing prednisolone by more than 5 mg/day or even 8 months after complete cessation — taper must be slow
• When amiodarone is absolutely essential: lowest possible dose + corticosteroids combination has been successfully used
• Regular follow-up: PFTs (disease progression), thyroid hormones (dysfunction), ECG (rhythm after amiodarone interruption)
• Screen for multi-system toxicity at time of APT diagnosis (thyroid, liver, eye)
• Vitamin E: attenuates Am-induced pulmonary fibrosis experimentally — not standard of care

Prognosis and Outcome

• Diagnosis typically made ~2 months after first symptom appearance
• Mortality stratified by presentation:
  • Pneumonitis: ~10%
  • Hospitalised: 20–30%
  • ARDS: ~50%
  • All rates increase further in elderly patients
• Response to treatment typically within 1–6 months
• Imaging: >85% of infiltrates resolve; residual or progression to fibrosis in remainder
• Patient education about APT risk is essential; early diagnosis clearly improves outcome

Limitations of the Document

• 2010 narrative review — no meta-analysis, no RCT evidence for any treatment recommendation
• ACE inhibitor/ARB protection data from only two retrospective studies — not practice-changing
• KL-6 data from single study using low-dose amiodarone cohort — not generalizable to high-dose
• CT density threshold (>70 HU) from limited studies; absent in majority — unreliable as screening criterion
• Corticosteroid taper threshold (≤5 mg/day) based on case reports, not systematic data
• Significant overlap with 2004 Camus review in pathophysiology and clinical patterns

Key Concepts Mentioned

• concepts/Amiodarone-Pulmonary-Toxicity — primary topic; updated with 3-mechanism framework, amiodarone effect vs toxicity distinction, full taxonomy, quantitative epidemiology

Key Entities Mentioned

• entities/Amiodarone — causative drug

Wiki Pages Updated

• wiki/sources/amiodarone-pulmonary-drugsafety-2010.md — created (this file)
• wiki/concepts/Amiodarone-Pulmonary-Toxicity.md — updated with new mechanisms, taxonomy, epidemiology, KL-6, CT density, ACE/ARB data, corticosteroid taper caution
• wiki/entities/Amiodarone.md — source_count updated; source link added
• wiki/wikiindex.md — concept description updated
• wiki/sourceindex.md — new source entry added