Isosorbide dinitrate is a prodrug that is metabolized in the body to release nitric oxide (NO). Nitric oxide activates guanylyl cyclase, leading to increased levels of cyclic guanosine monophosphate (cGMP). This results in:

1. Vasodilation:
   • Relaxation of vascular smooth muscle, particularly in veins, reducing preload and myocardial oxygen demand.
   • Dilation of coronary arteries, improving blood flow to ischemic areas of the heart (Lippincott, Lange).
2. Reduction in Cardiac Workload:
   • By decreasing preload and afterload, ISDN reduces the workload on the heart, alleviating angina symptoms (BNF).

1. Angina Pectoris:
   • Used for the prevention and treatment of chronic stable angina and vasospastic angina (BNF).
2. Heart Failure:
   • Provides symptomatic relief in acute and chronic heart failure by reducing preload and pulmonary congestion (Lippincott).
3. Acute Coronary Syndromes:
   • Used in the management of unstable angina and myocardial infarction to improve coronary blood flow (Lange).

• Angina Prophylaxis:
  • Initial dose: 5–20 mg two to three times daily, titrated to response (max 120 mg/day) (BNF).
• Acute Angina Relief:
  • Sublingual tablets: 2.5–5 mg as needed, repeated every 5–10 minutes (max 3 doses in 15 minutes) (Lippincott).
• Heart Failure:
  • Initial dose: 10–20 mg three to four times daily, titrated to response (Lange).

Administration:

• Oral tablets should be taken with or without food.
• Sublingual tablets should be placed under the tongue and allowed to dissolve.
• A nitrate-free interval of 10–12 hours is recommended to prevent tolerance (BNF).

• Common: Headache (due to vasodilation), dizziness, flushing, and hypotension (Lippincott).
• Serious: Reflex tachycardia, methemoglobinemia (rare), and severe hypotension (Lange).

• Hypotension: Use with caution in patients with low blood pressure or volume depletion (BNF).
• Severe Aortic Stenosis: Avoid in patients with severe aortic stenosis due to risk of cardiovascular collapse (Lippincott).
• Pregnancy: Use only if benefits outweigh risks; limited data available (Lange).
• Tolerance: Prolonged use can lead to tolerance; ensure a nitrate-free interval of 10–12 hours (BNF).

• Phosphodiesterase-5 Inhibitors (e.g., sildenafil): Concomitant use can cause severe hypotension; contraindicated (Lippincott).
• Antihypertensives: Enhanced hypotensive effects when combined with other vasodilators or antihypertensive medications (Lange).
• Alcohol: May exacerbate hypotension and dizziness (BNF).

Isosorbide dinitrate is the generic name for this medication. It is marketed under various brand names, including Isordil® and Dilatrate-SR®. Generic versions are widely available and cost-effective.