From the Research
For new-onset atrial fibrillation (AF) due to hyperthyroidism, the recommended dose of diltiazem is typically 0.13 mg/kg IV over 2 minutes initially, as this dose has been associated with significantly improved times to achieve heart rate control compared to lower doses. This recommendation is based on the most recent and highest quality study available, which found that diltiazem bolus dosing ≥ 0.13 mg/kg was associated with improved heart rate control without increasing the risk of hypotension or bradycardia 1.
Key Considerations
- The dose of 0.13 mg/kg IV is recommended as an initial bolus dose, with the option to repeat if needed after 15 minutes.
- After rate control is achieved, a continuous infusion of 5-15 mg/hour can be started, or transition to oral diltiazem at 30-60 mg every 6-8 hours, adjusted based on heart rate response.
- When switching to maintenance therapy, extended-release formulations can be used at 120-360 mg daily in divided doses.
- It's essential to monitor blood pressure closely during administration as hypotension is a potential side effect.
- Concurrent treatment of the underlying hyperthyroidism with anti-thyroid medications is crucial, as resolving the hyperthyroid state will often lead to spontaneous conversion to normal sinus rhythm.
Rationale
The study by 1 provides the most recent and highest quality evidence for the recommended dose of diltiazem in new-onset AF due to hyperthyroidism. The study found that a dose of 0.13 mg/kg IV was associated with improved heart rate control and did not increase the risk of hypotension or bradycardia. This dose is lower than the traditional recommended dose of 0.25 mg/kg IV, but has been shown to be effective and safer in terms of reducing the risk of hypotension.
Additional Considerations
- Other studies, such as 2, 3, 4, and 5, provide additional information on the use of diltiazem in AF, but are not as relevant to the specific question of the recommended dose in new-onset AF due to hyperthyroidism.
- The study by 2 found that low-dose diltiazem (≤ 0.2 mg/kg) was as effective as the standard dose in controlling rapid AF and reduced the risk of hypotension.
- The study by 3 discussed the management of AF in hyperthyroidism, but did not provide specific guidance on the recommended dose of diltiazem.
- The studies by 4 and 5 discussed the use of diltiazem in AF, but did not provide specific guidance on the recommended dose in new-onset AF due to hyperthyroidism.