Isosorbide Dinitrate 💊

ℹ️ About

Always check the BNF link here 📖 for the latest guidance.

⚙️ Mode of Action

• Nitric oxide (NO) donor → increases intracellular cGMP in vascular smooth muscle → vasodilation (mainly venous, but also arterial at higher doses) → reduced preload, afterload, and myocardial oxygen demand.

💊 Indications & Dose

• Acute angina / left ventricular failure: IV infusion (Isoket®) initially 2–10 mg/hour, increased as needed up to 20 mg/hour with close haemodynamic monitoring.
• Chronic stable angina (PO): 20–40 mg orally TDS in divided doses (max 240 mg/day). Ensure a nitrate-free interval to avoid tolerance.

⚠️ Interactions

• Concurrent use with PDE-5 inhibitors (sildenafil, tadalafil, vardenafil) may cause severe, potentially fatal hypotension 💥.
• Potentiates effects of other antihypertensives and alcohol.

🔎 Cautions

• Low blood pressure or hypovolaemia.
• Severe aortic stenosis, hypertrophic obstructive cardiomyopathy (HOCM), pericardial tamponade 🫀.
• Close monitoring required if given IV or sublingually.

🚫 Contraindications

• Marked hypotension, shock, or hypovolaemia.
• Severe aortic stenosis or other obstructive cardiomyopathies.
• Concurrent PDE-5 inhibitor use.

❗ Side Effects

• Headache (very common) 🤕
• Reflex tachycardia 💓
• Hypotension, dizziness, flushing 📉
• Tolerance with continuous therapy >24h (hence nitrate-free period needed).

📚 References

• BNF - Isosorbide Dinitrate