What is the appropriate dose of Diltiazem (diltiazem) for a 208-pound female patient with atrial fibrillation (afib) and tachycardia, with a heart rate of 145 beats per minute?

From the Guidelines

For a 208-pound (approximately 94 kg) female with atrial fibrillation and a heart rate of 145 beats per minute, I recommend starting with intravenous diltiazem at a dose of 0.25 mg/kg (about 23-24 mg) administered over 2 minutes, as supported by the 2011 ACCF/AHA/HRS focused updates incorporated into the ACC/AHA/ESC 2006 guidelines for the management of patients with atrial fibrillation 1. If the heart rate remains above 100 beats per minute after 15 minutes, a second bolus of 0.35 mg/kg (about 33 mg) can be given. Once the heart rate is controlled, transition to oral diltiazem, typically starting at 30 mg three to four times daily, with titration based on heart rate response. Continuous cardiac monitoring is essential during IV administration to watch for hypotension or bradycardia. Assess blood pressure before each dose, as diltiazem can cause significant hypotension, especially in patients who are volume depleted or on other antihypertensive medications. Diltiazem works by blocking calcium channels in the heart, which slows conduction through the AV node, thereby reducing ventricular rate in atrial fibrillation. This medication should be used cautiously in patients with heart failure, hypotension, or sick sinus syndrome, and dose adjustments may be needed in patients with liver or kidney dysfunction, as noted in the ACC/AHA/ESC 2006 guidelines for the management of patients with atrial fibrillation 1. It's also important to consider the patient's overall clinical context and adjust the treatment plan accordingly, taking into account the potential risks and benefits of different treatment strategies, as discussed in the 2005 ACC/AHA guideline update for the diagnosis and management of chronic heart failure in the adult 1. The use of diltiazem for rate control in atrial fibrillation is supported by multiple guidelines and studies, including the 2001 ACC/AHA/ESC guidelines for the management of patients with atrial fibrillation 1 and the 2003 management of newly detected atrial fibrillation: a clinical practice guideline from the American Academy of Family Physicians and the American College of Physicians 1. However, the most recent and highest-quality study, the 2011 ACCF/AHA/HRS focused updates incorporated into the ACC/AHA/ESC 2006 guidelines for the management of patients with atrial fibrillation 1, provides the most up-to-date guidance on this topic. Key points to consider when using diltiazem for rate control in atrial fibrillation include:

• Initial dose: 0.25 mg/kg IV over 2 minutes
• Second dose: 0.35 mg/kg IV after 15 minutes if heart rate remains above 100 beats per minute
• Oral dosing: 30 mg three to four times daily, with titration based on heart rate response
• Monitoring: continuous cardiac monitoring during IV administration, with assessment of blood pressure before each dose
• Cautions: use with caution in patients with heart failure, hypotension, or sick sinus syndrome, and adjust dose as needed in patients with liver or kidney dysfunction.

From the FDA Drug Label

The initial dose of diltiazem hydrochloride injection should be 0.25 mg/kg actual body weight as a bolus administered over 2 minutes (20 mg is a reasonable dose for the average patient). Patients with low body weights should be dosed on a mg/kg basis. The second bolus dose of diltiazem hydrochloride injection should be 0.35 mg/kg actual body weight administered over 2 minutes (25 mg is a reasonable dose for the average patient).

For a 208-pound female, the dose would be calculated as follows:

• Initial dose: 0.25 mg/kg x 94 kg (208 pounds) = 23.5 mg, which is close to the recommended 20-25 mg for the average patient.
• Second dose (if needed): 0.35 mg/kg x 94 kg = 32.9 mg, which is higher than the recommended 25 mg for the average patient.

The recommended initial dose for this patient would be approximately 20-25 mg. If a second dose is needed, it would be approximately 25 mg. However, the exact dose may vary depending on the patient's response to the initial dose and other clinical factors. 2

From the Research

Diltiazem Dosing for Atrial Fibrillation

• The dosing of diltiazem for atrial fibrillation (AF) is not explicitly stated in the provided studies, but its effectiveness compared to metoprolol is discussed 3, 4, 5, 6, 7.

Comparison of Diltiazem and Metoprolol

• Studies have shown that diltiazem is more effective in achieving rate control in patients with AF compared to metoprolol 3, 5, 6.
• Diltiazem has been found to have a more rapid onset of action and greater reduction in heart rate compared to metoprolol 3, 6.
• However, some studies have found no significant difference in the effectiveness of diltiazem and metoprolol for rate control in certain patient populations, such as those with heart failure with reduced ejection fraction 4.

Safety and Efficacy

• The safety profiles of diltiazem and metoprolol have been found to be similar, with no significant difference in the incidence of hypotension, bradycardia, or other adverse events 3, 4, 5, 6, 7.
• Diltiazem has been found to have a higher efficacy and shorter average onset time compared to metoprolol, with less impact on blood pressure 6.

Patient-Specific Factors

• The choice of rate control agent, including diltiazem, should be individualized based on patient-specific factors, such as underlying medical conditions, concomitant medications, and clinical presentation 7.
• For a 208-pound female patient with a heart rate of 145, the dosing of diltiazem would depend on various factors, including her medical history, kidney function, and other medications she may be taking, but this information is not provided in the studies 3, 4, 5, 6, 7.