What is the recommended dosage of nitroglycerin infusion per hour?

Nitroglycerin Infusion Dosage Recommendations

Intravenous nitroglycerin should be initiated at 5-10 mcg/min and titrated by 5-10 mcg/min every 3-5 minutes based on clinical response, with a typical maximum dose of 200 mcg/min. 1

Initial Dosing and Titration Protocol

• Starting dose: 5-10 mcg/min via continuous infusion through non-absorbing tubing 1
• Titration increments:
  • Increase by 5-10 mcg/min every 3-5 minutes initially 1
  • If no response at 20 mcg/min, can use increments of 10 and later 20 mcg/min 1
  • Once partial blood pressure response is observed, reduce the increment size and increase interval between adjustments 1

Titration End Points

1. Relief of symptoms (chest pain/ischemia) - primary endpoint
2. Blood pressure response:
   • Decrease in mean arterial pressure of 10% in normotensive patients
   • Decrease of 30% in hypertensive patients
   • Never titrate systolic BP below 90 mmHg or more than 25% below baseline 1
3. Heart rate: Avoid increases >10 beats/min or rates >110 beats/min 1
4. Pulmonary artery end-diastolic pressure: Decrease of 10-30% when monitored 1

Maximum Dosage Considerations

While there is no absolute upper limit, doses exceeding 200 mcg/min are associated with:

• Increased risk of hypotension
• Diminishing returns in efficacy
• Need to consider alternative therapy 1

Even prolonged infusion (2-4 weeks) at 300-400 mcg/min does not increase methemoglobin levels significantly 1.

Duration of Therapy and Tolerance Management

• Tolerance development: Typically occurs after 24 hours of continuous therapy 1, 2
• Management of tolerance:
  • Periodic increases in infusion rate may be required to maintain efficacy beyond 24 hours
  • Use non-tolerance-producing regimens (lower doses and intermittent dosing) when possible
  • Consider a nitrate-free interval of 10-14 hours to prevent complete tolerance 3

Discontinuation Protocol

• When patients are free of ischemic discomfort and other manifestations of ischemia for 12-24 hours, attempt to reduce the dose
• Transition to oral or topical nitrates when appropriate
• Discontinue IV nitroglycerin in patients who remain free of signs and symptoms of ischemia 1

Special Considerations and Contraindications

• Avoid in patients with:

  • Systolic BP <90 mmHg or 30 mmHg below baseline
  • Recent use of phosphodiesterase-5 inhibitors (sildenafil/vardenafil within 24h, tadalafil within 48h)
  • Marked bradycardia or tachycardia
  • Right ventricular infarction 1, 3

• Monitoring: Regular assessment of blood pressure, heart rate, and clinical symptoms is essential to prevent excessive hypotension, which can cause reflex tachycardia and worsen myocardial ischemia 3

Common Side Effects

• Headache
• Hypotension
• Reflex tachycardia

The combination of IV nitroglycerin with a beta-adrenergic blocker in appropriate patients may reduce the risk of undesired tachycardia 1.

Human Factors Note: When administering IV nitroglycerin, use non-absorbing tubing as significant adsorption of nitroglycerin can occur with polyvinylchloride tubing, resulting in lower than calculated delivered doses 4.