Monomil (Isosorbide Mononitrate, Diluted Ph. Eur.)

Isosorbide Mononitrate is used in the management of cardiovascular conditions that involve reduced blood flow to the heart.

• Angina pectoris: reduces frequency of chest pain episodes by improving coronary blood flow.
• Chronic heart failure: alleviates symptoms such as dyspnea and fatigue by decreasing cardiac workload.
• Stable angina: helps prevent angina attacks during physical exertion through sustained vasodilation.

• Isosorbide Mononitrate is a prodrug that is metabolized to release nitric oxide in vascular smooth muscle. The nitric oxide activates guanylate cyclase, increasing cyclic GMP levels, which leads to relaxation of smooth muscle cells, vasodilation of veins and arteries, and a consequent reduction in preload and afterload, lowering myocardial oxygen demand. This hemodynamic effect improves coronary perfusion without significantly increasing heart rate.

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

Common Side Effects

• Headache: throbbing pain often occurring shortly after dosing.
• Dizziness: sensation of light‑headedness or imbalance.
• Flushing: warmth and redness of the face or neck.
• Hypotension: mild drop in blood pressure causing faintness.
• Nausea: upset stomach or feeling of needing to vomit.
• Tachycardia: faster than normal heart rate.

Serious or Rare Side Effects

• Severe hypotension: marked blood pressure fall leading to syncope.
• Syncope: sudden loss of consciousness.
• Myocardial infarction: rare occurrence of heart attack.
• Allergic reaction: rash, itching, swelling, or difficulty breathing.
• Methemoglobinemia: abnormal hemoglobin causing cyanosis.

When prescribing Isosorbide Mononitrate, clinicians should consider several safety measures to minimize risk.

• Monitor blood pressure: check for excessive drops, especially after dose initiation.
• Avoid abrupt discontinuation: tapering reduces risk of rebound angina.
• Use cautiously in hepatic impairment: reduced metabolism may increase exposure.
• Assess concomitant use of PDE5 inhibitors: combined effect can cause profound hypotension.
• Pregnancy and lactation: prescribe only if benefits outweigh potential risks and after specialist consultation.
• Store at room temperature: keep in the original packaging, protect from moisture and direct sunlight.

Isosorbide Mononitrate interacts with several medicines; awareness of these interactions helps prevent adverse events.

Major Interactions (Avoid)

• Sildenafil, tadalafil or other PDE5 inhibitors: additive vasodilatory effect may cause severe hypotension.
• Other nitrates (e.g., nitroglycerin, isosorbide dinitrate): combined use can lead to dangerous blood pressure fall.
• Strong antihypertensives (e.g., intravenous nitroprusside): may produce uncontrolled hypotension.

Moderate Interactions (Monitor Closely)

• Beta‑blockers: may mask tachycardia signs of hypotension.
• Calcium channel blockers: can enhance vasodilatory response.
• Diuretics: may increase risk of volume depletion and low blood pressure.
• Alcohol: can potentiate hypotensive effect.