How to start Nitroglycerin (NTG) injection?

How to Start Nitroglycerin (NTG) Injection

Intravenous NTG should be initiated at a rate of 10 mcg per minute through continuous infusion via nonabsorbing tubing and increased by 10 mcg per minute every 3 to 5 minutes until symptom relief or blood pressure response is noted. 1

Initial Setup and Dosing

• Begin IV NTG at 10 mcg/min via continuous infusion using nonabsorbing tubing 1
• Titrate upward by 10 mcg/min increments every 3-5 minutes until one of the following occurs:
  • Relief of ischemic symptoms 1
  • Desired blood pressure response 1
  • Development of side effects (headache, hypotension) 1

Titration Algorithm

• If no response is seen at 20 mcg/min, continue with 10 mcg/min increments 1
• At higher doses, increments of 20 mcg/min may be used 1
• Once symptoms are relieved, no further dose increases are needed even if blood pressure hasn't changed significantly 1
• If symptoms persist, continue increasing until blood pressure response is observed 1
• When partial blood pressure response is observed, reduce the increment size and lengthen interval between increases 1

Maximum Dosing and Duration

• Although no official maximum dose is established, a ceiling of 200 mcg/min is commonly used 1
• Even prolonged infusion (2-4 weeks) at 300-400 mcg/min does not increase methemoglobin levels 1, 2
• Tolerance typically develops after 24 hours of continuous therapy 1
• For patients requiring NTG beyond 24 hours, periodic dose increases may be needed to maintain efficacy 1

Blood Pressure Parameters

• Do not titrate systolic BP below 110 mmHg in previously normotensive patients 1
• Do not reduce BP more than 25% below baseline mean arterial pressure in hypertensive patients 1
• Avoid NTG in patients with:
  • Initial systolic BP less than 90 mmHg 1
  • BP drop of 30 mmHg or more below baseline 1
  • Marked bradycardia or tachycardia 1

Contraindications and Precautions

• NTG is contraindicated after use of:
  • Sildenafil within previous 24 hours 1
  • Tadalafil within previous 48 hours 1
  • Vardenafil (wait until BP returns to baseline, typically 24 hours) 1
• Phosphodiesterase inhibitors can cause profound hypotension, MI, and even death when combined with nitrates 1

Transitioning from IV to Oral/Topical NTG

• When patients are free of ischemic symptoms for 12-24 hours, attempt to reduce IV NTG dose 1
• Convert to oral or topical nitrates within 24 hours in stabilized patients 1
• Use non-tolerance producing regimens (lower doses and intermittent dosing) 1
• Discontinue IV NTG in patients who remain free of signs and symptoms of ischemia 1
• If ischemia recurs during continuous therapy, increase dose and consider adding nitrate-free intervals 1

Managing Nitrate Tolerance

• Tolerance to hemodynamic effects is dose and duration dependent 1
• To minimize tolerance, use intermittent dosing schedules that provide nitrate-free intervals during each 24-hour period 3
• For recurrent ischemia during continuous therapy, responsiveness can often be restored by increasing the dose 1

Common Side Effects

• Headache 1
• Hypotension 1
• Abrupt cessation of IV NTG may cause exacerbation of ischemic changes on ECG, so use graded reduction 1