Amiodarone induced:
- Due to its iodine content, amiod. affects the thyroid
| Thyroid Status | Description |
|---|---|
| Hypo | More common than hyper |
| Hyper | |
| Euthyroid | Abnormal TFTs but patient clinically normal (most cases) |
(patients on amiod -⇒ check TFTs every 6 months)
XAI Amiodarone is a medication primarily used to treat and prevent a variety of serious heart rhythm disorders, such as ventricular tachycardia and ventricular fibrillation. It is also used for atrial fibrillation and other supraventricular arrhythmias. Amiodarone works by affecting the electrical signals in the heart to restore a normal heart rhythm.
Key Information:
- Class: Antiarrhythmic (Class III)
- Mechanism of Action: Amiodarone prolongs the phase 3 of the cardiac action potential, which is the repolarization phase. It blocks potassium channels, leading to a prolonged refractory period and decreased excitability of the heart muscle. It also has effects on sodium and calcium channels and has some beta-blocking properties.
- Administration: Can be given orally or intravenously.
- Half-life: Extremely long, ranging from 20 to 100 days, which means it can take a long time to reach steady-state levels and also a long time to be cleared from the body after discontinuation.
Indications:
- Ventricular tachycardia (VT)
- Ventricular fibrillation (VF)
- Atrial fibrillation (AF) (especially in cases where other treatments are ineffective or contraindicated)
- Supraventricular tachycardia (SVT)
Side Effects:
Amiodarone has a wide range of potential side effects, some of which can be serious. These include:
- Pulmonary toxicity: Can cause interstitial lung disease, including pulmonary fibrosis.
- Thyroid dysfunction: Both hypothyroidism and hyperthyroidism can occur due to the high iodine content of the drug.
- Liver toxicity: Elevated liver enzymes and, in rare cases, severe liver damage.
- Ocular effects: Corneal deposits, optic neuropathy, and visual disturbances.
- Skin reactions: Photosensitivity and blue-gray skin discoloration.
- Cardiac effects: Bradycardia, heart block, and worsening of arrhythmias.
- Neurological effects: Tremors, peripheral neuropathy, and ataxia.
Monitoring:
Due to its potential for serious side effects, patients on amiodarone require regular monitoring, including:
- Liver function tests
- Thyroid function tests
- Chest X-ray and pulmonary function tests
- Ophthalmologic exams
- ECG monitoring
Drug Interactions:
Amiodarone has numerous drug interactions, including with:
- Warfarin: Increases the risk of bleeding.
- Digoxin: Increases digoxin levels, leading to toxicity.
- Other antiarrhythmics: Can increase the risk of arrhythmias.
- Statins: Increases the risk of myopathy.
Special Considerations:
- Long Half-Life: Due to its long half-life, amiodarone can remain in the body for weeks to months after discontinuation, which can prolong both therapeutic effects and side effects.
- Use in Pregnancy: Amiodarone is generally avoided in pregnancy due to potential risks to the fetus, including thyroid dysfunction and developmental issues.
Summary:
Amiodarone is a potent antiarrhythmic medication with a broad spectrum of activity but also a significant risk of side effects. It is typically reserved for use in patients with life-threatening arrhythmias or those who have not responded to other treatments. Regular monitoring is essential to manage the risks associated with its use.