Ismn (Isosorbide Mononitrate)

Isosorbide mononitrate acts within the nitrate class to prevent myocardial ischemia and to support cardiac function in chronic disease.

• Angina pectoris: reduces frequency and severity of chest pain episodes by improving myocardial oxygen supply.
• Chronic heart failure: alleviates dyspnea and fatigue by decreasing cardiac preload and afterload.
• Prophylaxis of angina attacks: maintains stable coronary blood flow to prevent episodic ischemia.

• Isosorbide mononitrate is enzymatically converted to nitric oxide, which activates soluble guanylate cyclase in vascular smooth muscle cells. This raises cyclic GMP levels, leading to relaxation of arterial and venous vessels, reduced systemic vascular resistance, and decreased cardiac preload and afterload, thereby enhancing myocardial oxygen delivery.

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

Common Side Effects

• Headache: throbbing pain often occurring shortly after dosing.
• Dizziness or light‑headedness: related to vasodilation and blood pressure fall.
• Flushing: warm sensation with reddening of skin.
• Nausea or abdominal discomfort.
• Hypotension: especially when standing.
• Palpitations: awareness of heartbeat.

Serious or Rare Side Effects

• Severe hypotension leading to syncope.
• Myocardial infarction in susceptible patients.
• Life‑threatening arrhythmias.
• Allergic reactions such as rash, itching, or angioedema.
• Methemoglobinemia: bluish discoloration of skin and mucous membranes.
• Persistent severe headache unresponsive to analgesics.

Before initiating therapy, clinicians should evaluate patient‑specific factors and monitor for potential complications.

• Blood pressure monitoring: check baseline and periodic readings to avoid excessive hypotension.
• Concomitant nitrate use: avoid combined therapy to prevent profound vasodilation.
• Hepatic impairment: use with caution as metabolism may be reduced.
• Renal impairment: adjust dosing if severe renal dysfunction is present.
• Orthostatic precautions: advise patients to rise slowly from sitting or lying positions.
• Store at room temperature: keep in the original container, protect from moisture and direct sunlight.

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

Major Interactions (Avoid)

• Other nitrates (e.g., nitroglycerin): risk of severe hypotension.
• Phosphodiesterase‑5 inhibitors (e.g., sildenafil, tadalafil): additive vasodilatory effect leading to dangerous blood pressure drops.
• Guanylate cyclase stimulators: synergistic vasodilation.

Moderate Interactions (Monitor Closely)

• Antihypertensive agents (beta‑blockers, ACE inhibitors): may enhance blood pressure‑lowering effect.
• Diuretics: can increase orthostatic hypotension.
• Alcohol: potentiates vasodilatory response.
• CYP3A4 inhibitors (e.g., erythromycin, ketoconazole): may raise plasma levels.
• Smoking: induces metabolic clearance, reducing drug exposure.