What is the recommended dose of Cardizem (diltiazem) for this patient with atrial fibrillation?

Recommended Diltiazem Dosing for Atrial Fibrillation

For a patient with atrial fibrillation, the recommended dose of diltiazem is 0.25 mg/kg IV over 2 minutes for initial control, followed by a continuous infusion of 5-15 mg/hour, with an oral maintenance dose of 120-360 mg daily in divided doses. 1

Intravenous Diltiazem Administration

Initial Bolus Dose:

• 0.25 mg/kg (actual body weight) IV over 2 minutes 1
• May repeat 0.35 mg/kg over 2 minutes if first dose is inadequate 1
• Low-dose option (≤0.2 mg/kg) may be considered for patients at risk of hypotension while maintaining similar efficacy 2

Continuous Infusion:

• Start at 5-15 mg/hour 1
• Titrate based on heart rate response 1
• Maximum recommended infusion rate: 15 mg/hour 3

Oral Maintenance Therapy

Standard Dosing:

• 120-360 mg daily in divided doses 1
• Extended-release formulations available 1

Transition from IV to Oral:

• Begin oral therapy while IV infusion continues
• Continue IV infusion for approximately 4 hours after first oral dose 4
• Median effective oral dose is 300 mg/day when transitioning from IV 4

Monitoring Parameters

Target Heart Rate:

• 60-80 beats per minute at rest 1, 5
• <110 beats per minute with moderate activity 1, 5

Safety Monitoring:

• Blood pressure (watch for hypotension)
• Heart rhythm (watch for bradycardia)
• Signs of heart failure (especially in patients with reduced ejection fraction)

Special Considerations

Efficacy:

• Response rate of approximately 93-94% for acute rate control 6
• Medium-dose diltiazem (240 mg/day) is comparable to digoxin at rest but superior during exercise 7

Contraindications:

• Heart failure with reduced ejection fraction (HFrEF) 1
• Severe hypotension
• High-grade AV block without pacemaker

Combination Therapy:

• If diltiazem alone is insufficient, consider adding digoxin 7
• Combined therapy provides better rate control both at rest and during exercise than either agent alone 7

Common Pitfalls to Avoid

1. Using diltiazem in patients with heart failure with reduced ejection fraction (HFrEF) - contraindicated due to negative inotropic effects 1

2. Inadequate monitoring for hypotension - occurs in 18-42% of patients depending on dose 2

3. Failure to adjust dosing in renal impairment - may require lower doses or extended intervals

4. Overlooking drug interactions, particularly with other negative chronotropic agents

5. Not considering the transition from IV to oral therapy - requires overlap period for successful transition 4

By following these dosing recommendations and monitoring parameters, diltiazem can effectively control ventricular rate in atrial fibrillation while minimizing adverse effects.