Monorem (Isosorbide Mononitrate)

Isosorbide mononitrate is used in the nitrate vasodilator class to treat conditions related to myocardial oxygen demand.

• Angina pectoris: reduces frequency of chest pain episodes by decreasing myocardial oxygen demand.
• Chronic stable angina: improves exercise tolerance and delays onset of symptoms.
• Chronic heart failure (off‑label in some regions): may alleviate symptoms of congestion and improve functional capacity.

• Isosorbide mononitrate is a prodrug that is enzymatically converted to nitric oxide after oral absorption. The released nitric oxide activates guanylate cyclase in vascular smooth‑muscle cells, increasing cyclic GMP levels. Elevated cGMP leads to relaxation of arterial and venous smooth muscle, producing vasodilation, lowering preload and afterload, and consequently reducing myocardial oxygen consumption. The effect is sustained over 24 hours, allowing once‑daily dosing in many regimens.

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

Common Side Effects

• Headache
• Dizziness
• Flushing
• Nausea

Serious or Rare Side Effects

• Severe hypotension
• Syncope
• Severe allergic reaction (e.g., rash, angioedema)

When prescribing isosorbide mononitrate, clinicians should observe several safety considerations.

• Blood pressure assessment: measure baseline systolic and diastolic values before initiation.
• Concomitant nitrates: avoid using with other nitrate preparations to prevent additive hypotension.
• PDE‑5 inhibitors: do not combine with sildenafil, tadalafil or similar agents.
• Renal impairment: adjust therapy in patients with severe renal dysfunction.
• Patient counseling: advise on rising slowly from sitting to reduce orthostatic dizziness.
• Store at below 25°C: keep in the original pack, protect from moisture.

Isosorbide mononitrate interacts with several drug classes; awareness of these interactions helps prevent adverse events.

Major Interactions (Avoid)

• Other nitrates (e.g., nitroglycerin): additive vasodilatory effect leading to profound hypotension.
• Phosphodiesterase‑5 inhibitors (sildenafil, tadalafil): risk of severe blood pressure drop.
• Potent antihypertensives (e.g., hydralazine) used together: may cause excessive hypotension.

Moderate Interactions (Monitor Closely)

• Alcohol: can enhance vasodilatory response and dizziness.
• Diuretics: may increase risk of volume depletion and low blood pressure.
• Other antihypertensive agents (beta‑blockers, ACE inhibitors): require blood pressure monitoring.