Ismo Retard (Isosorbide Mononitrate)

Isosorbide mononitrate is used in the management of coronary artery disease‑related conditions, primarily to alleviate angina.

• Angina pectoris (prevention): reduces the frequency and severity of chest pain episodes.
• Chronic stable angina (symptom control): improves exercise tolerance and daily activity capacity.
• Ischemic heart disease (adjunct therapy): complements other anti‑anginal agents to optimise myocardial oxygen balance.

• Isosorbide mononitrate is a prodrug that is metabolised to release nitric oxide. The nitric oxide activates guanylate cyclase, increasing cyclic GMP levels in vascular smooth muscle, leading to relaxation of arteries and veins, decreased preload and afterload, and consequently lower myocardial oxygen consumption.

Isosorbide mononitrate may be associated with a range of adverse reactions, varying from mild to serious.

Common Side Effects

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

Serious or Rare Side Effects

• Severe hypotension: marked drop in blood pressure requiring medical attention.
• Syncope: transient loss of consciousness.
• Allergic reactions: rash, itching, or swelling that may progress to anaphylaxis.
• Stevens‑Johnson syndrome: rare severe skin reaction.
• Myocardial infarction: very rare but reported in isolated cases.

Before initiating therapy, clinicians should consider several safety aspects.

• Dose titration: start with a low dose and increase gradually to minimise hypotension.
• Concomitant PDE‑5 inhibitors: avoid combined use due to risk of profound blood pressure fall.
• Blood pressure monitoring: watch for symptomatic hypotension, especially after the first dose.
• Renal and hepatic function: assess and adjust if significant impairment is present.
• Pregnancy and lactation: use only if the potential benefit justifies the potential risk to the fetus or infant.
• 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)

• Phosphodiesterase‑5 inhibitors (e.g., sildenafil, tadalafil): may cause severe hypotension.
• Other nitrates (e.g., nitroglycerin, isosorbide dinitrate): additive vasodilatory effect leading to dangerous blood pressure drops.

Moderate Interactions (Monitor Closely)

• Antihypertensive agents (ACE inhibitors, beta‑blockers, calcium channel blockers): may enhance blood pressure‑lowering effect.
• Alcohol: can potentiate hypotensive response.
• Diuretics: may increase volume depletion and orthostatic symptoms.