From the FDA Drug Label
The FDA drug label does not answer the question.
From the Research
For new-onset atrial fibrillation (AF) due to hyperthyroidism, the recommended dose of diltiazem is typically 0.25 mg/kg IV over 2 minutes initially (approximately 15-20 mg for most adults), followed by a second bolus of 0.35 mg/kg (approximately 20-25 mg) if needed after 15 minutes. If rate control is achieved, this can be followed by a continuous infusion of 5-15 mg/hour, titrated to heart rate. For oral maintenance therapy, start with 30 mg three to four times daily, which can be titrated up to 360 mg total daily dose based on heart rate response. When administering diltiazem, monitor blood pressure closely as hypotension is a common side effect. Also monitor heart rate and ECG for excessive bradycardia or AV block. It's essential to note that while diltiazem helps control the rapid ventricular rate in AF, treating the underlying hyperthyroidism with anti-thyroid medications (such as methimazole or propylthiouracil) is crucial for long-term management, as the AF may resolve once euthyroid status is restored 1. Beta-blockers may be preferred in some hyperthyroid patients, but diltiazem is a good alternative when beta-blockers are contraindicated. Some studies suggest that new-onset AF can be a predictor of subsequent hyperthyroidism 2, and the risk of ischemic stroke is increased in patients with hyperthyroidism-induced AF 3. However, the provided evidence does not directly address the dose of diltiazem for new-onset AF due to hyperthyroidism, but based on general guidelines and the most recent study available 1, the recommended dose can be applied. Key considerations in managing AF due to hyperthyroidism include:
- Controlling the heart rate with medications like diltiazem
- Treating the underlying hyperthyroidism
- Monitoring for potential complications like ischemic stroke
- Individualizing treatment based on patient-specific factors, as suggested by recent reviews 4.