How should I dilute a 25 mg (5 mL) nitroglycerin ampule for IV infusion to obtain a 100 µg/mL concentration and what infusion rate provides the standard starting dose?

Nitroglycerin IV Dilution and Infusion Protocol

To achieve a 100 µg/mL concentration from your 25 mg (5 mL) ampule, add the entire ampule to 245 mL of either D5W or 0.9% NaCl to create a total volume of 250 mL, then start the infusion at 5 µg/min (3 mL/hr) using non-absorbing tubing. 1

Dilution Preparation

• Add the complete 25 mg nitroglycerin ampule (5 mL) to 245 mL of diluent to achieve a final volume of 250 mL with a concentration of 100 µg/mL 1
• Acceptable diluents: Either Dextrose 5% Injection or Sodium Chloride 0.9% Injection 1
• Critical safety warning: Never administer nitroglycerin as a direct IV injection—it must be diluted prior to infusion 1
• Do not mix nitroglycerin with other drugs in the same solution 1
• Invert the container several times after adding the nitroglycerin to ensure uniform dilution 1

Starting Infusion Rate

• Initial dose: 5 µg/min when using non-absorbing (non-PVC) tubing 1
• At 100 µg/mL concentration, this equals 3 mL/hr on a volumetric infusion pump 1
• Important context: Historical studies used PVC tubing and started at 25 µg/min or higher, but PVC absorbs significant amounts of nitroglycerin, requiring higher doses 1
• Modern non-absorbing tubing delivers drug more efficiently, necessitating lower starting doses to avoid hypotension 1

Titration Algorithm

• Increase by 5 µg/min increments every 3-5 minutes until you observe a partial blood pressure response 1
• Once reaching 20 µg/min without response, you may increase increments to 10 µg/min, then 20 µg/min 1
• After observing partial response: Reduce the increment size and lengthen the interval between increases 1
• Maximum concentration: Do not exceed 400 µg/mL if you need to concentrate the solution for fluid restriction 1
• Critical equipment note: If you change the concentration, you must flush or replace the entire infusion set before using the new concentration to avoid delayed delivery 1

Special Patient Considerations

• Angina patients without heart failure may be hypersensitive and respond fully to doses as low as 5 µg/min, requiring especially careful titration 1
• Recent evidence suggests high-dose strategies (≥100 µg/min) achieve blood pressure targets faster in acute pulmonary edema (57% reaching target within 1 hour vs 22% with low-dose), though this requires careful monitoring 2
• The European Society of Cardiology recommends nitroglycerin as a vasodilator option in acute heart failure with adequate blood pressure (SBP >85 mmHg) 3

Mandatory Monitoring Requirements

• Continuous blood pressure and heart rate monitoring in all patients 1
• Pulmonary capillary wedge pressure monitoring when appropriate 1
• Stop nitroglycerin immediately if systolic blood pressure drops below 85 mmHg 3
• Maintain adequate systemic blood pressure and coronary perfusion pressure throughout infusion 1

Common Pitfalls to Avoid

• Using PVC tubing without dose adjustment: PVC absorbs 40-80% of nitroglycerin, leading to underdosing if you use non-PVC starting doses 1
• Failing to flush tubing after concentration changes: The old concentration can remain in the dead space for minutes to hours depending on flow rate, causing unpredictable dosing 1
• Inadequate monitoring: Nitroglycerin has no fixed optimal dose—each patient requires individual titration based on hemodynamic response 1
• Mixing with other medications: This can cause incompatibilities and unpredictable drug delivery 1