ISDN Concentration Calculation
The concentration is approximately 111 mcg/mL (or 0.111 mg/mL).
Mathematical Calculation
To determine the concentration when 10 mg of ISDN is diluted in 90 mL of D5W:
- Total drug amount: 10 mg = 10,000 mcg
- Total volume: 90 mL
- Concentration: 10,000 mcg ÷ 90 mL = 111.1 mcg/mL
- Alternative expression: 10 mg ÷ 90 mL = 0.111 mg/mL
Critical Clinical Context
Important Limitation of ISDN for IV Use
Nitroglycerin, not ISDN, is the standard nitrate for intravenous administration. The American College of Cardiology explicitly states that nitroglycerin is the only nitrate formulation available for intravenous use in the United States and recommends using nitroglycerin instead of ISDN for intravenous nitrate therapy 1.
Standard Nitroglycerin IV Preparation (Preferred Alternative)
If intravenous nitrate therapy is needed, the proper approach is 2, 1:
- Standard preparation: 1 mg nitroglycerin in 250 mL D5W = 4 mcg/mL concentration 2
- Starting dose: 5-10 mcg/min, titrated by 5-10 mcg/min every 3-5 minutes 1
- Maximum dose: Typically 200 mcg/min 1
- Use non-PVC tubing for administration 1
Critical Safety Parameters for IV Nitrate Administration
When administering any intravenous nitrate, strict monitoring is essential 1:
- **Avoid systolic BP <90 mmHg** or >30 mmHg below baseline 1
- In normotensive patients: Do not reduce systolic BP below 110 mmHg 1
- In hypertensive patients: Do not reduce mean arterial pressure by >25% 1
- Contraindications include: Sildenafil use within 24 hours, tadalafil within 48 hours, initial systolic BP <90 mmHg 1
Oral ISDN Dosing (Standard Route)
ISDN is typically administered orally, not intravenously 2:
- Starting dose: 20 mg three times daily 2, 1
- Target dose: 40 mg three times daily after 2-4 weeks if tolerated 2, 1
- Essential: Provide a nitrate-free interval of at least 10-14 hours daily to prevent tolerance 1
Common Pitfall
The primary pitfall here is attempting to use ISDN intravenously when nitroglycerin is the appropriate IV nitrate formulation 1. While the mathematical concentration of your preparation is 111 mcg/mL, this is not a standard or recommended clinical preparation for intravenous use in contemporary practice.