How do I prepare a Nitroglycerin (NTG) infusion in a 50 ml syringe?

Preparing Nitroglycerin Infusion in a 50 mL Syringe

To prepare a nitroglycerin infusion in a 50 mL syringe, dilute the concentrated nitroglycerin solution to achieve a final concentration between 50-400 mcg/mL using either 5% dextrose or 0.9% sodium chloride, ensuring the concentration allows for precise titration at your intended starting dose of 5-10 mcg/min. 1

Standard Concentration Preparation

Common Dilution Options

• 50 mcg/mL concentration: Mix 2.5 mg nitroglycerin in 50 mL of diluent (allows finer dose titration at lower rates) 1
• 100 mcg/mL concentration: Mix 5 mg nitroglycerin in 50 mL of diluent (standard concentration for most clinical scenarios) 1
• Maximum concentration: Do not exceed 400 mcg/mL 1

Diluent Selection

• Use either 5% Dextrose Injection or 0.9% Sodium Chloride Injection 1
• Do not mix nitroglycerin with other drugs in the same syringe 1
• Invert the syringe several times after mixing to ensure uniform dilution 1

Critical Equipment Considerations

Syringe and Tubing Material

• Use non-absorbing (non-PVC) tubing and syringes whenever possible 2, 1
• PVC materials absorb significant amounts of nitroglycerin, reducing delivered dose by up to 85% at slow infusion rates 3, 4, 5
• If PVC tubing must be used, expect to need substantially higher infusion rates to achieve clinical effect 3, 4
• Flush or replace the infusion set completely before changing to a new concentration to avoid delayed delivery of the new dose 1

Infusion Pump Requirements

• Must use an infusion pump capable of exact and constant delivery 1
• Volumetric infusion pumps are preferred for precise control 1
• At lower flow rates with non-PVC tubing, more solution than calculated may be delivered—monitor closely 3

Dosing Strategy with 50 mL Syringe

Initial Dosing

• Start at 5-10 mcg/min when using non-absorbing equipment 2, 1
• If using PVC tubing (not recommended), start at 10-20 mcg/min due to absorption losses 6

Titration Protocol

• Increase by 5-10 mcg/min every 3-5 minutes until symptom relief or blood pressure response 6, 2, 1
• At 20 mcg/min without response, use larger increments of 10 mcg/min, then 20 mcg/min 6, 2, 1
• Once partial response occurs, reduce increment size and lengthen intervals between increases 6, 2, 1
• Stop titrating if symptoms resolve—no need to continue for blood pressure effect alone 2

Maximum Dose

• Commonly used ceiling is 200 mcg/min 6, 2, 7
• Doses up to 300-400 mcg/min have been safely used for prolonged periods without increasing methemoglobin levels 6, 7

Safety Parameters (Absolute Requirements)

Blood Pressure Thresholds

• **Do not use if systolic BP <90 mmHg** or >30 mmHg below baseline 6, 2, 7
• Target systolic BP: not less than 110 mmHg in normotensive patients 6, 2, 7
• In hypertensive patients: do not reduce mean arterial pressure by >25% 2, 7

Contraindications

• Marked bradycardia or tachycardia 6, 2, 7
• Right ventricular infarction (patients critically dependent on preload) 2, 7
• Sildenafil use within 24 hours or tadalafil within 48 hours (risk of profound hypotension and death) 2, 7

Practical Calculation Example

For a 50 mL syringe with 100 mcg/mL concentration (5 mg total):

• At 10 mcg/min: infusion rate = 0.1 mL/hr × 60 = 6 mL/hr
• At 50 mcg/min: infusion rate = 30 mL/hr
• At 100 mcg/min: infusion rate = 60 mL/hr
• A 50 mL syringe at 100 mcg/mL will last 30 minutes at 100 mcg/min 1

Common Pitfalls to Avoid

• Never give nitroglycerin as a direct IV bolus—it must be diluted and infused 1
• Do not assume dose equivalence between PVC and non-PVC systems—actual delivered dose varies dramatically 3, 4, 5
• Tolerance develops after 24 hours of continuous infusion—may require dose increases or conversion to intermittent dosing 6, 2, 7
• Flush the line completely when changing concentrations, as it can take minutes to hours for new concentration to reach the patient depending on flow rate and dead space 1
• Some patients (especially those with normal left ventricular filling pressures) may be hypersensitive and respond fully to doses as low as 5 mcg/min—titrate cautiously 1