Diltiazem Dosing for Atrial Fibrillation
For atrial fibrillation, the recommended intravenous diltiazem dose is 0.25 mg/kg over 2 minutes (may repeat with 0.35 mg/kg after 15 minutes if needed), followed by a continuous infusion of 5-15 mg/hour; the oral maintenance dose ranges from 120-360 mg daily of extended-release formulation. 1
Intravenous Diltiazem Dosing
Initial Management
- For acute rate control in atrial fibrillation with rapid ventricular response, administer diltiazem 0.25 mg/kg (actual body weight) IV over 2 minutes 1
- If inadequate response, may repeat with 0.35 mg/kg IV over 2 minutes 1
- Follow with continuous infusion at 5-15 mg/hour for ongoing rate control 1
- Higher weight-based dosing (≥0.13 mg/kg) achieves faster heart rate control compared to lower doses 2
Efficacy Considerations
- Diltiazem typically achieves heart rate control (<100 bpm) within 2-7 minutes of administration 1
- IV diltiazem is superior to amiodarone or digoxin for achieving rapid ventricular rate control in acute atrial fibrillation 3
- Patients receiving diltiazem experience shorter time to rate control (median 3 hours) compared to digoxin (6 hours) or amiodarone (7 hours) 3
Oral Diltiazem Dosing
Maintenance Therapy
- Oral maintenance dose: 120-360 mg daily of extended-release (ER) formulation 1
- Immediate-release formulation has a half-life of 3-4.5 hours 1
- Extended-release formulation has a half-life of 4-9.5 hours 1
Combination Therapy
- Medium-dose diltiazem (240 mg/day) combined with digoxin provides effective rate control both at rest and during exercise 4
- High-dose diltiazem (360 mg/day) provides better rate control but has more side effects (75% of patients) 4
Important Considerations and Precautions
Contraindications
- Avoid diltiazem in patients with heart failure with reduced ejection fraction (HFrEF) 1
- Use caution in patients with renal or hepatic impairment 1
- Monitor for hypotension, which occurs more frequently with standard (>0.2 to ≤0.3 mg/kg) and high doses (>0.3 mg/kg) compared to low doses (≤0.2 mg/kg) 5
Monitoring
- Assess heart rate response both at rest and during exercise 1
- Monitor blood pressure during administration to detect hypotension 5
- Therapeutic plasma concentrations of 79-294 ng/mL are required to produce 20-40% reduction in heart rate 6
Pharmacokinetics
- IV diltiazem has a half-life of 3-5 hours 1
- Clearance appears to be dose-dependent, decreasing with increasing infusion rates 6
- Strong relationship exists between plasma concentration and heart rate reduction 6
Alternative Rate Control Options
- Beta blockers (metoprolol, atenolol, esmolol) are alternative first-line agents 1
- Verapamil (another non-dihydropyridine calcium channel blocker) can be used at 5-10 mg IV over ≥2 minutes, with oral maintenance of 180-480 mg daily (ER) 1
- Digoxin may be considered in patients with heart failure, with loading dose of 0.25-0.5 mg IV followed by 0.0625-0.25 mg daily maintenance 1
Remember that diltiazem is primarily used for rate control in atrial fibrillation and does not convert patients back to sinus rhythm 1.