What is the diltiazem dose for coronary vasospasm by intravenous (IV) infusion?

Diltiazem Dosing for Coronary Vasospasm

For coronary vasospasm, intravenous diltiazem should be administered as a 0.25 mg/kg bolus over 2 minutes followed by a continuous infusion starting at 5-10 mg/hour, titrated up to 15 mg/hour as needed. 1

Initial Bolus Dosing

• Administer 0.25 mg/kg (approximately 15-20 mg for an average adult) as an IV bolus over 2 minutes 1
• If response is inadequate after 15 minutes, a second bolus of 0.35 mg/kg (approximately 25 mg) may be administered 1
• Some patients with low body weight may respond to an initial lower dose of 0.15 mg/kg, though duration of action may be shorter 1

Continuous Infusion Protocol

• Immediately following bolus administration, begin continuous IV infusion 1
• Start with 5-10 mg/hour (5 mg/hour may be appropriate for some patients) 1
• Titrate in 5 mg/hour increments up to a maximum of 15 mg/hour based on clinical response 1
• Infusion may be maintained for up to 24 hours (longer durations have not been well studied) 1

Dilution Guidelines

For proper administration, dilute diltiazem appropriately:

• 125 mg in 100 mL diluent = 1 mg/mL concentration (administer at 10-15 mL/hour for 10-15 mg/hour dose) 1
• 250 mg in 250 mL diluent = 0.83 mg/mL concentration (administer at 12-18 mL/hour for 10-15 mg/hour dose) 1
• 250 mg in 500 mL diluent = 0.45 mg/mL concentration (administer at 22-33 mL/hour for 10-15 mg/hour dose) 1

Efficacy in Coronary Vasospasm

• Diltiazem is highly effective for coronary artery spasm, with studies showing 30-70% reduction in angina frequency 2
• Long-term studies demonstrate up to 90% reduction in cardiovascular events in patients with coronary vasospasm treated with diltiazem 2
• Diltiazem works by causing marked vascular smooth muscle relaxation with minimal effects on myocardial contractility 3

Monitoring and Precautions

• Monitor for hypotension, which is the most common adverse effect 4
• Watch for bradycardia and potential worsening of heart failure in predisposed patients 4
• Avoid in patients with AV block greater than first degree or significant SA node dysfunction 4
• Contraindicated in patients with pre-excited atrial fibrillation or flutter (WPW syndrome) 4
• Have resuscitation equipment available during administration 4

Alternative Treatment Considerations

• For coronary vasospasm, the American College of Cardiology/American Heart Association recommends calcium channel blockers as first-line therapy 5
• Nitrates can be used in combination with calcium channel blockers for patients with very active disease 5
• Alpha-receptor blockers may benefit patients not responding completely to calcium channel blockers and nitrates 5

Clinical Pearls

• Diltiazem is usually very responsive for coronary spasm treatment, with moderate to high doses (180-360 mg per day orally for maintenance therapy) recommended 5
• Diltiazem effectively reverses preexisting vasospasm in coronary artery conduits 6
• For patients with unstable angina due to coronary vasospasm, continuous IV diltiazem has shown a 94% cumulative effective ratio 7