Isosorbide Mononitrate Milpharm (Isosorbide Mononitrate, Diluted Ph. Eur.)

Isosorbide Mononitrate belongs to the organic nitrate class and is used to manage coronary artery disease‑related angina.

• Chronic stable angina pectoris: improves myocardial oxygen supply by reducing cardiac preload and afterload, thereby decreasing the frequency of angina attacks.
• Variant (Prinzmetal) angina: provides prophylactic relief through sustained vasodilation of coronary vessels.
• Post‑myocardial infarction angina prophylaxis: helps prevent recurrent chest pain during the recovery phase.

• Isosorbide mononitrate is metabolized to release 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, lowering preload and afterload, and enhancing coronary blood flow to improve myocardial oxygen delivery.

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

Common Side Effects

• Headache: throbbing or pressure‑type pain, often transient.
• Dizziness or light‑headedness: related to blood pressure reduction.
• Flushing: warm sensation with reddening of the skin.
• Nausea or abdominal discomfort.
• Hypotension: mild drop in blood pressure, especially after the first dose.

Serious or Rare Side Effects

• Severe hypotension: marked blood pressure fall requiring medical attention.
• Syncope: fainting episodes due to sudden circulatory changes.
• Tachycardia: rapid heart rate as a compensatory response.
• Allergic reactions: rash, pruritus, or angioedema.
• Worsening angina or myocardial ischemia despite therapy.

Before initiating therapy, clinicians should evaluate cardiovascular status and consider patient‑specific factors.

• Assess blood pressure: ensure baseline values are adequate to tolerate vasodilation.
• Monitor for hypotension: especially after dose escalation or when combined with other vasodilators.
• Avoid abrupt discontinuation: taper to prevent rebound angina.
• Caution in hepatic impairment: dose adjustment may be required.
• Use with care in elderly patients: increased sensitivity to blood pressure changes.
• Store at ambient temperature: keep in the original container, 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, isosorbide dinitrate): additive vasodilatory effect leading to severe hypotension.
• Phosphodiesterase‑5 inhibitors (e.g., sildenafil, tadalafil): risk of profound blood pressure fall.
• Alcohol: potentiates hypotensive response.

Moderate Interactions (Monitor Closely)

• Antihypertensive agents (ACE inhibitors, beta‑blockers): may enhance blood pressure lowering.
• Diuretics: can increase risk of dehydration and hypotension.
• CYP3A4 inhibitors (e.g., erythromycin, ketoconazole): may raise plasma levels of isosorbide mononitrate.
• Antiplatelet drugs: monitor for increased bleeding tendency.