Isosorbide Mononitrate Accord-Uk (Isosorbide Mononitrate)

Isosorbide Mononitrate is indicated for conditions involving myocardial oxygen demand where vasodilation improves blood flow.

• Chronic stable angina pectoris: reduces frequency of angina attacks and improves exercise tolerance.
• Angina prophylaxis: provides sustained nitrate therapy to prevent ischemic episodes during daily activities.

• After oral absorption, isosorbide mononitrate is metabolized to nitric oxide, which activates guanylate cyclase in vascular smooth muscle. The resulting increase in cyclic GMP leads to relaxation of arterial and venous smooth muscle, decreasing preload and afterload, and thereby improving myocardial oxygen balance and relieving ischemia.

Isosorbide Mononitrate may cause a range of adverse reactions, most of which are dose‑related and reversible upon discontinuation.

Common Side Effects

• Headache: mild to moderate, often transient.
• Dizziness or light‑headedness.
• Flushing of the skin.
• Hypotension: especially when standing.
• Nausea or gastrointestinal discomfort.
• Palpitations or tachycardia.

Serious or Rare Side Effects

• Severe hypotension leading to syncope.
• Acute myocardial infarction in susceptible patients.
• Life‑threatening allergic reactions (anaphylaxis, angioedema).
• Life‑threatening arrhythmias.
• Methemoglobinemia (very rare).
• Persistent severe headache unresponsive to therapy.

When prescribing or dispensing isosorbide mononitrate, consider the following safety measures.

• Dose titration: start with a low dose and adjust gradually based on tolerance.
• Concomitant phosphodiesterase‑5 inhibitors: avoid due to risk of profound hypotension.
• Renal impairment: monitor renal function and adjust dose if needed.
• Hepatic impairment: use with caution and monitor liver enzymes.
• Avoid abrupt discontinuation: may precipitate rebound angina.
• Store at ambient temperature: keep below 25°C in the original container, protect from moisture.

Isosorbide mononitrate can interact with several drug classes, requiring attention to avoid adverse outcomes.

Major Interactions (Avoid)

• Sildenafil and other PDE‑5 inhibitors: may cause severe hypotension.
• Other organic nitrates or nitroglycerin: additive vasodilatory effect leading to dangerous blood pressure drops.
• Potent antihypertensive agents (e.g., ACE inhibitors, beta‑blockers): may enhance blood‑pressure‑lowering effects.

Moderate Interactions (Monitor Closely)

• Diuretics: increase risk of orthostatic hypotension.
• Alcohol: can potentiate vasodilatory effects and dizziness.
• Azole antifungals (e.g., ketoconazole): may affect metabolic clearance of the nitrate.