Ismo (Isosorbide Mononitrate)

Isosorbide Mononitrate is used within the anti‑anginal drug class to manage coronary artery disease and related chest pain.

• Stable angina pectoris: decreases the frequency and severity of chest pain episodes.
• Chronic angina: improves exercise capacity and reduces reliance on short‑acting nitrates.
• Angina prophylaxis: provides long‑term prevention of angina attacks in patients with known coronary disease.

• 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 walls, producing vasodilation that lowers preload and afterload, thereby decreasing myocardial oxygen consumption and alleviating angina symptoms.

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

Common Side Effects

• Headache: throbbing pain often occurring shortly after dosing.
• Dizziness or light‑headedness: related to blood pressure reduction.
• Flushing: warm sensation and reddening of the skin.
• Nausea: mild gastrointestinal upset.
• Palpitations: awareness of heartbeats.

Serious or Rare Side Effects

• Severe hypotension: marked drop in blood pressure requiring medical attention.
• Syncope: sudden loss of consciousness.
• Myocardial infarction: rare but possible in susceptible patients.
• Life‑threatening arrhythmias: irregular heart rhythms.
• Allergic reactions: rash, itching, or swelling.
• Stevens‑Johnson syndrome: severe skin reaction, extremely rare.

Before initiating therapy with Ismo, clinicians should consider several safety measures.

• Cardiovascular assessment: evaluate baseline blood pressure and heart rate.
• Discontinuation warning: avoid abrupt cessation to prevent rebound angina.
• Blood pressure monitoring: check regularly, especially after dose changes.
• Hepatic impairment: use with caution in patients with liver dysfunction.
• Concomitant PDE‑5 inhibitors: contraindicated due to risk of profound hypotension.
• Store at room temperature: keep in the original container, protect from moisture and direct sunlight.

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

Major Interactions (Avoid)

• Phosphodiesterase‑5 inhibitors (e.g., sildenafil): may cause severe hypotension.
• Other nitrates (e.g., nitroglycerin): additive vasodilatory effect leading to dangerous blood pressure drops.
• Nitroglycerin patches or sprays: same risk of excessive vasodilation.

Moderate Interactions (Monitor Closely)

• Antihypertensive agents (e.g., ACE inhibitors, beta‑blockers): may enhance blood pressure lowering.
• Diuretics: can increase the risk of orthostatic hypotension.
• Alcohol: potentiates vasodilatory effects and dizziness.