Isomonit Retard (Isosorbide Mononitrate)

Isosorbide Mononitrate belongs to the organic nitrate class and is used to manage ischemic heart disease.

• Chronic stable angina: reduces the frequency and severity of angina attacks during daily activities.
• Angina pectoris: improves exercise tolerance by decreasing myocardial oxygen demand.
• Prophylaxis of angina: provides long‑term prevention of anginal episodes when taken regularly.

• 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 walls, producing vasodilation, lowering preload and afterload, and thereby decreasing myocardial oxygen consumption.

Isosorbide mononitrate may cause a range of adverse reactions, from mild to serious.

Common Side Effects

• Headache: throbbing pain often occurring shortly after dosing.
• Dizziness or light‑headedness: related to blood pressure reduction.
• Flushing: warm sensation and reddening of the skin.
• Nausea: mild gastrointestinal upset.
• Palpitations: awareness of heartbeat acceleration.
• Hypotension: measurable drop in blood pressure.

Serious or Rare Side Effects

• Severe hypotension: marked blood pressure fall requiring medical attention.
• Syncope: sudden loss of consciousness.
• Tachycardia: rapid heart rate that may be symptomatic.
• Allergic reaction: rash, itching, or swelling of the face and throat.
• Methemoglobinemia: rare disorder causing reduced oxygen delivery.

Patients should be counseled on safety measures before starting therapy.

• Blood pressure monitoring: check regularly to detect excessive hypotension.
• Orthostatic precautions: rise slowly from sitting or lying positions to avoid dizziness.
• Hepatic impairment: adjust therapy if liver function is compromised.
• Renal impairment: use with caution in patients with reduced kidney function.
• Concomitant antihypertensives: assess for additive blood‑pressure lowering effects.
• Store at ambient temperature: keep below 25 °C, retain in original packaging, protect from moisture and direct sunlight.

Isosorbide mononitrate can interact with several drug classes, altering its safety profile.

Major Interactions (Avoid)

• Other nitrates (e.g., nitroglycerin): risk of profound hypotension.
• Phosphodiesterase‑5 inhibitors (e.g., sildenafil): may cause severe blood‑pressure drops.
• Strong vasodilators: additive hypotensive effect.

Moderate Interactions (Monitor Closely)

• Antihypertensive agents (beta‑blockers, ACE inhibitors): monitor blood pressure.
• Alcohol: may enhance vasodilatory response.
• Diuretics: potential for volume depletion and hypotension.
• Certain antihistamines: may increase headache incidence.
• CYP3A4 inhibitors (e.g., ketoconazole): possible increase in plasma levels.