What is the loading dose of Amiodarone (antiarrhythmic medication) administered orally (PO)?

From the Guidelines

The oral loading dose of amiodarone is typically 400-600 mg daily, divided into 2-3 doses, for 2-4 weeks, followed by a maintenance dose of 100-200 mg daily. For a standard approach, start with 400 mg twice daily for 1-2 weeks, then 200 mg twice daily for 1-2 weeks, before transitioning to a maintenance dose of 200 mg once daily 1. Take amiodarone with food to reduce gastrointestinal side effects. Monitor for adverse effects including thyroid dysfunction, pulmonary toxicity, liver abnormalities, and corneal deposits. Baseline and periodic testing should include thyroid function tests, liver function tests, pulmonary function tests, chest X-ray, and ophthalmologic examination. Amiodarone has a very long half-life (approximately 58 days) due to its lipophilic nature and tissue accumulation, which explains why loading is necessary to achieve therapeutic levels quickly. The drug works by blocking multiple ion channels, including potassium, sodium, and calcium channels, as well as alpha and beta-adrenergic receptors, making it effective for both ventricular and atrial arrhythmias.

Key Considerations

• The dosage guidelines for amiodarone vary depending on the indication, with ventricular arrhythmia typically requiring 800-1600 mg per day in divided doses until a total of 10 g has been given, followed by 200-400 mg per day 1.
• Atrial fibrillation may be treated with 600-800 mg per day in divided doses until a total of 10 g has been given, followed by 200 mg per day 1.
• It is essential to monitor for potential adverse effects, including bradycardia, QT prolongation, torsades de pointes, gastrointestinal upset, constipation, hypothyroidism, hyperthyroidism, pulmonary fibrosis, hepatic toxicity, corneal deposits, optic neuritis, peripheral neuropathy, photosensitivity, and adult respiratory distress syndrome after cardiac or noncardiac surgery 1.
• Amiodarone is a substrate of and inhibits P-glycoprotein and CYP2C9, CYP2D6, and CYP3A4, and is a substrate for CYP3A4 and CYP2C8, which may lead to interactions with other medications 1.

Monitoring and Maintenance

• Regular monitoring of thyroid function, liver function, pulmonary function, and ophthalmologic examination is necessary to minimize the risk of adverse effects.
• The maintenance dose of amiodarone should be adjusted based on the patient's response and tolerance to the medication.
• Patients should be educated on the potential adverse effects of amiodarone and the importance of regular monitoring and follow-up appointments.

From the Research

Amiodarone Loading PO

• The oral loading protocol for amiodarone can vary, with one study using 50 mg/kg per day for 3 days, then 30 mg/kg per day for 2 days, followed by maintenance therapy of 300 to 400 mg twice daily 2.
• High dose oral amiodarone loading (greater than 1,800 mg/day) has been used for unstable patients with incessant ventricular tachyarrhythmias, but its use in more stable patients has also been studied 2.
• A comparative study found that combined intravenous and oral loading with amiodarone can shorten its onset of action, with a shorter time to optimal ventricular arrhythmia control and a lower cumulative dose required 3.
• The safety and tolerance of high dose oral amiodarone loading have been evaluated, with one study finding that it was well tolerated in 15 of 16 patients, with no significant side effects during the loading period 2.

Monitoring and Safety

• Monitoring of amiodarone use is crucial due to its potential for serious adverse effects, including thyroid abnormalities, pulmonary fibrosis, and transaminitis 4, 5, 6.
• Laboratory monitoring rates for ALT, TSH, and T4 were significantly higher in a pharmacist-managed group than in usual care, with improved monitoring of recommended laboratory tests and PFTs 4.
• A retrospective audit found that monitoring of thyroid, liver, and pulmonary function tests in patients on amiodarone was less than ideal, likely due to lack of awareness of current guidelines 6.
• Routine monitoring is recommended for patients taking amiodarone, including laboratory tests and pulmonary function tests, to ensure safe and effective use of the medication 5.