What infusion rate (mL/hr) should be set for a 50 kg female receiving 10 mg isosorbide dinitrate (Isoket) diluted in 90 mL of 5% dextrose in water (D5W) via a Soluset?

Isosorbide Dinitrate (Isoket) Infusion Rate Calculation

For a 50 kg female patient receiving 10 mg isosorbide dinitrate in 90 mL D5W, the infusion rate should be set between 5.4-27 mL/hour (equivalent to 0.6-3.0 mcg/kg/min), starting at the lower end and titrating upward based on blood pressure response.

Dosing Framework for Intravenous Isosorbide Dinitrate

Standard Dosing Range

• Intravenous isosorbide dinitrate is typically administered at 1.5-6.0 mcg/kg/min for acute cardiovascular conditions, with bolus doses ranging from 3.0-40.0 mcg/kg 1
• For a 50 kg patient, this translates to 75-300 mcg/min (or 4.5-18 mg/hour) 1

Concentration Calculation for Your Preparation

• Your preparation contains 10 mg in 90 mL, which equals approximately 111 mcg/mL
• To deliver the therapeutic range of 75-300 mcg/min:
  • Minimum rate: 75 mcg/min ÷ 111 mcg/mL = 0.68 mL/min (approximately 40 mL/hour)
  • Maximum rate: 300 mcg/min ÷ 111 mcg/mL = 2.7 mL/min (approximately 162 mL/hour)

Critical Dosing Considerations

Starting Dose Recommendation

• Begin at 0.125-0.332 mg/min (1.5-6.0 mcg/kg/min) for controlled infusion, which produces modest blood pressure reduction with predictable titration 1
• For your 50 kg patient at the lower end (1.5 mcg/kg/min = 75 mcg/min), this equals approximately 40 mL/hour
• At the higher end (6.0 mcg/kg/min = 300 mcg/min), this equals approximately 162 mL/hour 1

Titration Strategy

• Continuous controlled infusion causes a 17% reduction in systolic blood pressure and 11% drop in diastolic blood pressure, which is more modest and controllable than bolus administration 1
• The desired blood pressure level can be readily titrated and maintained in a stable, predictable manner with continuous infusion 1
• Monitor blood pressure every 5-15 minutes during initial titration to avoid excessive hypotension 1

Pharmacokinetic Considerations

Rapid Onset and Short Half-Life

• Isosorbide dinitrate has an elimination half-life of only 9-10 minutes after intravenous administration, requiring continuous infusion for sustained effect 2
• Hemodynamic effects are usually apparent at 15 minutes, peak between 30-120 minutes, and persist for up to 240 minutes 3

D5W as Vehicle

• D5W is an appropriate diluent for isosorbide dinitrate infusions 4
• When D5W serves as a medication vehicle, monitor blood glucose levels regardless of infusion rate, especially in diabetic patients 4
• The relatively low volume (90 mL) and slow infusion rate minimize concerns about glucose load 4, 5

Safety Monitoring

Hemodynamic Monitoring

• Moderate venodilation (decreased central venous pressure) accompanies the blood pressure response 1
• Heart rate is not appreciably altered with appropriate dosing 1
• Avoid reducing systolic blood pressure below 105/60 mm Hg to prevent excessive hypotension 1

Common Pitfalls to Avoid

• Do not use bolus administration for initial dosing, as it causes more dramatic blood pressure drops (23% systolic, 25% diastolic) that are harder to control 1
• Avoid rapid infusion rates without adequate blood pressure monitoring 1
• Be aware that orthostatic effects are more pronounced when patients are standing versus supine 3

Practical Starting Recommendation

For a 50 kg female patient, start the infusion at 40-50 mL/hour (delivering approximately 1.5-2.0 mcg/kg/min), then titrate upward by 10-20 mL/hour increments every 15-30 minutes based on blood pressure response, up to a maximum of 162 mL/hour if needed 1. This approach provides safe, predictable blood pressure control while minimizing the risk of excessive hypotension 1.