Monomil (Isosorbide Mononitrate, Diluted Ph. Eur.)

Monomil, a nitrate vasodilator, is used in cardiovascular conditions that benefit from reduced myocardial oxygen demand.

• Angina pectoris: decreases the frequency and severity of chest pain episodes.
• Chronic heart failure: improves exercise tolerance and reduces symptoms of fluid overload.
• Stable ischemic heart disease: helps prevent angina attacks during physical exertion.

• 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, producing vasodilation that lowers preload and afterload and enhances myocardial oxygen supply.

Isosorbide mononitrate may cause a range of adverse reactions.

Common Side Effects

• Headache: mild to moderate throbbing pain.
• Dizziness or light‑headedness, especially on standing.
• Flushing: warm sensation with reddening of the skin.
• Nausea or upset stomach.
• Hypotension: transient drop in blood pressure.
• Palpitations or tachycardia.

Serious or Rare Side Effects

• Severe hypotension leading to syncope.
• Myocardial infarction in patients with unstable coronary disease.
• Allergic reactions such as rash, pruritus or angioedema.
• Methemoglobinemia: rare discoloration of blood.
• Life‑threatening arrhythmias in susceptible individuals.

Before initiating therapy, clinicians should evaluate cardiovascular status and consider potential risks.

• Assess blood pressure: monitor for excessive drops.
• Avoid abrupt discontinuation: taper to prevent rebound angina.
• Monitor hepatic function: dose adjustment may be needed in severe impairment.
• Caution with concomitant phosphodiesterase‑5 inhibitors: risk of profound hypotension.
• Review all concurrent antihypertensive agents: adjust as needed.
• Store at room temperature: keep in the original pack, protect from moisture.

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

Major Interactions (Avoid)

• Other nitrates (e.g., nitroglycerin): additive vasodilation causing severe hypotension.
• Phosphodiesterase‑5 inhibitors (e.g., sildenafil): risk of profound blood pressure fall.
• Sodium nitrite: increased risk of methemoglobinemia.

Moderate Interactions (Monitor Closely)

• Antihypertensive agents (ACE inhibitors, beta‑blockers): may enhance blood pressure lowering.
• Azole antifungals (e.g., ketoconazole): can raise plasma levels of isosorbide mononitrate.
• Rifampin or other enzyme inducers: may reduce drug efficacy.