Ismo (Isosorbide Mononitrate)

• Isosorbide mononitrate is used in the management of coronary artery disease‑related angina, where it helps prevent ischemic chest pain.
• Angina pectoris: reduces the frequency and severity of chest pain episodes.
• Chronic stable angina: improves exercise tolerance and delays onset of pain.
• Prevention of angina attacks: provides long‑acting prophylaxis for patients with known coronary artery disease.

• Isosorbide mononitrate is metabolized to nitric oxide, which activates soluble guanylate cyclase in vascular smooth muscle. The resulting increase in cyclic GMP causes relaxation of veins and arteries, lowering preload and afterload, and thereby reducing myocardial oxygen consumption and relieving angina.

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

Common Side Effects

• Headache: often transient and mild.
• Dizziness or light‑headedness.
• Flushing of the face or neck.
• Low blood pressure (hypotension).
• Nausea or upset stomach.
• Palpitations or rapid heartbeat.

Serious or Rare Side Effects

• Severe hypotension leading to fainting.
• Syncope (sudden loss of consciousness).
• Myocardial infarction in susceptible patients.
• Life‑threatening arrhythmias.
• Allergic reactions such as rash or angioedema.
• Methemoglobinemia (very rare).

• Before prescribing Isosorbide mononitrate, clinicians should consider several safety factors.
• Assess cardiovascular status: monitor blood pressure and heart rate prior to initiation.
• Avoid abrupt discontinuation: taper the dose to prevent rebound angina.
• Use with caution in hepatic impairment: dose adjustment may be required.
• Avoid concomitant use of phosphodiesterase‑5 inhibitors: risk of profound hypotension.
• Pregnancy and lactation: safety not established; use only if clearly needed.
• Store at ambient temperature: keep in the original container, protect from moisture and light.

Isosorbide mononitrate can interact with several drug classes, requiring attention to avoid adverse outcomes.

Major Interactions (Avoid)

• Sildenafil, tadalafil, or other PDE‑5 inhibitors: may cause severe hypotension.
• Other nitrates (e.g., nitroglycerin, isosorbide dinitrate): additive vasodilatory effect leading to dangerous blood pressure drops.
• Alcohol: can potentiate hypotensive effects.

Moderate Interactions (Monitor Closely)

• Antihypertensive agents (ACE inhibitors, beta‑blockers): may enhance blood‑pressure‑lowering effect.
• Diuretics: combined effect may cause excessive hypotension.
• Azole antifungals (e.g., ketoconazole): may increase plasma concentrations of isosorbide mononitrate.