Cardiovascular system (see Adverse Reactions): ECG alterations, imposing as QT prolongation (in dependence of prolonged repolarisation) possibly in connection with the development of a U-wave as well as prolongation and deformation of the T-wave, demonstrate the pharmacological activity of amiodarone.
There is an increased risk of "torsades de pointes" in case of an excessive QT prolongation.
As a consequence of the pharmacological action of amiodarone sinus bradycardia, which may be more pronounced in elderly patients or in case of an impaired sinus node function may occur. In exceptional cases sinus node arrest may develop.
If pronounced bradycardia or sinus node arrest occurs, the treatment must be discontinued.
Proarrhythmic effects in the form of new or enhanced cardiac arrhythmia that can be life-threatening have been described.
It is important, but difficult, to differentiate a lack of efficacy of the medicinal product from a proarrhythmic effect. Proarrhythmic effects during treatment with amiodarone mainly occur in connection with QT-prolonging factors, such as medicinal product interactions and/or electrolyte imbalance (see Interactions and Adverse Reactions). Despite QT prolongation amiodarone shows a low torsadogenic activity.
Severe bradycardia (see Interactions): Cases of severe, potentially life-threatening bradycardia and heart block have been observed when amiodarone is used in combination with sofosbuvir in combination with another hepatitis C virus direct acting antiviral (DAA), such as daclatasvir, simeprevir, or ledipasvir. Therefore, co-administration of these agents with amiodarone is not recommended.
If concomitant use with amiodarone cannot be avoided, it is recommended that patients are closely monitored when initiating sofosbuvir in combination with other DAAs. Patients who are identified as being at high risk of bradyarrhythmia should be continuously monitored for at least 48 hours in an appropriate clinical setting after initiation of the concomitant treatment with sofosbuvir.
Due to the long half-life of amiodarone, appropriate monitoring should also be carried out for patients who have discontinued amiodarone within the past few months and are to be initiated on sofobusvir in combination with other DAAs.
Patients receiving these hepatitis C medicines with amiodarone, with or without other medicines that lower heart rate, should be warned of the symptoms of bradycardia and heart block and should be advised to seek urgent medical advice if they experience them.
Hyperthyroidism (see Precautions and Adverse Reactions): Hyperthyroidism may occur during therapy or up to several months after discontinuation of amiodarone therapy. The following, usually mild symptoms, should be considered by the physician: Weight loss, tachycardia, tremor, nervousness, increased sweating and heat intolerance, recurrence of arrhythmia or angina pectoris, heart failure.
The clinical diagnosis of hyperthyroidism is confirmed by proof of evidently decreased ultrasensitive TSH as well as increased T3 and T4 values. In the case of hyperthyroidism, therapy should be withdrawn.
Improvement occurs within several months after discontinuation of treatment and is accompanied by a normalisation of the thyroid function test.
In severe cases (sometimes fatal) an individual emergency treatment with antithyroid medicinal products, beta-blockers and/or corticosteroids has to be started.
Lung (see Adverse Reactions): There is the risk of developing severe inflammatory pneumopathy (hypersensitivity, pneumonitis, alveolar or interstitial pneumonitis) during therapy with amiodarone. Non-productive cough and dyspnoea are common symptoms of the previously mentioned pulmonary changes. Furthermore, weight loss, fever, weakness may occur.
Therefore, thoracic roentgenography and pulmonary function test should be performed prior to the onset of treatment. These examinations should be repeated at intervals of approximately 3-6 months in the further therapeutic course.
These examinations should also be carried out if dyspnoea (symptom of a possible pulmotoxic effect) occurs.
In patients with severe lung disease, pulmonary function is to be monitored more frequently, as these patients have a worsened prognosis if pulmotoxic effects occur.
By proof of hypersensitivity pneumonitis, amiodarone is to be withdrawn immediately and therapy with corticosteroids initiated.
By proof of alveolar/interstitial pneumonia, treatment should be carried out with corticosteroids and the dose reduced or - if possible - amiodarone should be discontinued.
If amiodarone is withdrawn early, interstitial pneumonia usually recedes.
Very rare cases of severe, in some cases fatal, respiratory complications (acute respiratory distress syndrome), usually right after surgical interventions have been reported (see also Interactions).
Liver (see Adverse Reactions): Monitoring of liver enzymes (transaminases) based on liver function tests is recommended once amiodarone therapy is started. Regular checks of liver function should be performed during therapy.
Acute liver disease (including severe hepatocellular insufficiency or liver failure, in some cases with fatal outcome) and chronic liver disease can occur with the oral and intravenous dose form of amiodarone (with intravenous application already during the first 24 hours).
Therefore, the dose should be reduced or amiodarone discontinued if transaminase levels increase to values exceeding 3 times the norm.
Clinical and laboratory signs of chronic liver disease due to oral amiodarone therapy may be minimal (cholestatic jaundice, hepatomegaly, transaminases increased to up to 5 times the norm). Liver dysfunction is reversible after discontinuation of amiodarone, but cases with fatal outcome have been reported.
Severe bullous skin reactions (see Adverse Reactions): Life-threatening or even fatal skin reactions: Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). If symptoms or signs of SJS, TEN are present (such as progressive skin rash, often with blisters or mucosal lesions), amiodarone must be discontinued immediately.
Neuromuscular disorders (see Adverse Reactions): Amiodarone can cause peripheral neuropathy and/or myopathy. These usually disappear a few months after discontinuation of amiodarone therapy, but may not be completely reversible in some cases.
Eyes (see Adverse Reactions): Regular ophthalmological investigations, including fundoscopy and slit-lamp examinations have to be performed during treatment with amiodarone.
If blurred or decreased vision occurs, complete ophthalmologic examination including fundoscopy should be promptly performed.
Appearance of optic neuropathy and/or optic neuritis requires amiodarone withdrawal due to the potential progression to blindness.
Medicinal product interactions (see Interactions): The concomitant use of amiodarone with the following medicinal products is not recommended: Beta-blockers, calcium channel blockers with antiarrhythmic effect (verapamil, diltiazem), laxatives which can cause hypokalaemia.
Amiodarone is an inhibitor of cytochrome P450 (CYP) 3A4. Therefore statins that are metabolised by CYP3A4 (e.g. simvastatin, atorvastatin, lovastatin) should not be used concomitantly with amiodarone.