ISDN Drip Administration
Isosorbide dinitrate (ISDN) is administered as a continuous intravenous infusion, but nitroglycerin is strongly preferred for IV nitrate therapy in the United States, as ISDN is not the standard formulation for intravenous use. 1
Preferred Alternative: Nitroglycerin IV
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
Nitroglycerin IV Protocol
- Starting dose: 5-10 mcg/min (some guidelines suggest 10-20 mcg/min) 2, 1
- Titration: Increase by 5-10 mcg/min every 3-5 minutes based on blood pressure and symptom response 2, 1
- Maximum dose: Typically 200 mcg/min 1
- Preparation: Dilute in D5W or normal saline using non-PVC tubing 1
- Half-life: Only several minutes, making it ideal for acute titration 1
ISDN IV Administration (When Used)
When ISDN is used intravenously (primarily outside the United States or in research settings):
Dosing Regimens
- Bolus administration: 0.25 to 2.5 mg (3.0 to 40.0 mcg/kg) for acute situations 3
- Continuous infusion: 0.125 to 0.332 mg/min (1.5 to 6.0 mcg/kg/min) 3
- Alternative regimen: Rapid bolus of 2 to 6 mg followed by infusion of 2 to 5 mg/hr 4
Administration Technique
- Slow titration with frequent blood pressure monitoring is mandatory to avoid large drops in systolic blood pressure 2
- An arterial line is not routinely required but facilitates titration in patients with borderline pressures 2
- Continuous infusion provides more modest and stable blood pressure reduction compared to bolus dosing 3
Critical Blood Pressure Parameters
Indications Based on Systolic BP
- SBP >110 mmHg: Recommended for use 2
- SBP 90-110 mmHg: May be used with extreme caution 2
- SBP <90 mmHg: Absolute contraindication 2, 5
Blood Pressure Targets During Titration
- Do not reduce systolic BP below 90 mmHg or >30 mmHg below baseline 1
- In previously normotensive patients, do not titrate systolic BP below 110 mmHg 1
- In hypertensive patients, do not reduce mean arterial pressure by >25% 1
Absolute Contraindications
- Sildenafil use within 24 hours 1, 5
- Tadalafil use within 48 hours 1, 5
- Initial systolic BP <90 mmHg 1, 5
- Marked bradycardia (<50 bpm) or tachycardia 1
- Right ventricular infarction or inferior wall MI with RV involvement (extreme caution required due to risk of profound hypotension) 1, 5
Critical Monitoring Requirements
Hemodynamic Monitoring
- Frequent blood pressure measurements are essential to avoid inadvertent systemic hypotension, which can cause reflex tachycardia and worsen myocardial ischemia 1
- Monitor for paradoxical bradycardia and increased angina pectoris 5
- Assess for signs of volume depletion before initiation 5
Special Populations Requiring Extreme Caution
- Patients with inferior wall MI: Frequently associated with right ventricular infarction—these patients depend on adequate RV preload and can experience profound hypotension 2, 1
- Volume-depleted patients: Already hypotensive patients are at high risk 5
- Hypertrophic cardiomyopathy: Nitrate therapy may aggravate angina 5
Tolerance Development
- Tachyphylaxis is common after 24-48 hours of continuous therapy, necessitating incremental dosing 2
- Significant coronary vasodilating effects persist after 2-day infusion, but tolerance develops within 5 days 6
- A nitrate-free interval of at least 10-14 hours daily is essential to prevent tolerance development 1
Adverse Effects Management
Common Side Effects
- Headache: Most frequent side effect; can be managed with aspirin or acetaminophen without compromising efficacy 5
- Hypotension: May be accompanied by lightheadedness, especially when standing 5
- Dizziness: Related to blood pressure changes 5
Management of Hypotension
- Leg elevation 1
- Rapid fluid administration 1
- Atropine if severe 1
- Dose adjustment or temporary discontinuation 5
Clinical Context for Use
Primary Indications
- Acute heart failure with SBP >110 mmHg: Decreases left and right heart filling pressures, systemic vascular resistance, and improves dyspnea 2
- Unstable angina refractory to conventional therapy: Effective for recurrent chest pain at rest 4
- Acute hypertension following cardiopulmonary bypass 3