Imdur (Isosorbide Mononitrate)

Imdur (isosorbide mononitrate) is used in the management of coronary artery disease, specifically for angina control.

• Stable angina: reduces the frequency and severity of angina episodes by improving myocardial oxygen balance.
• Chronic stable angina: provides long‑term prophylaxis to lessen the need for nitroglycerin rescue medication.
• Angina pectoris: helps maintain exercise tolerance and quality of life in patients with documented coronary artery disease.

• Isosorbide mononitrate is a nitric oxide donor that is metabolized to release nitric oxide in vascular smooth muscle. The nitric oxide activates guanylate cyclase, increasing cyclic GMP levels, which leads to relaxation of arterial and venous smooth muscle, reducing preload and afterload and consequently decreasing myocardial oxygen demand.

Isosorbide mononitrate may cause a range of adverse reactions. Most are mild and reversible, but some can be serious and require immediate medical attention.

Common Side Effects

• Headache: throbbing pain often occurring shortly after the first dose.
• Dizziness or light‑headedness: related to blood pressure lowering.
• Flushing: warmth and redness of the face or neck.
• Nausea: mild gastrointestinal upset.
• Hypotension: especially when standing quickly.
• Palpitations: awareness of heartbeats.

Serious or Rare Side Effects

• Severe hypotension: marked drop in blood pressure causing fainting.
• Syncope: sudden loss of consciousness.
• Tachycardia: rapid heart rate that may be symptomatic.
• Allergic reactions: rash, itching, swelling, or difficulty breathing.
• Worsening angina or myocardial infarction: rare but possible.
• Methemoglobinemia: abnormal hemoglobin affecting oxygen delivery.

Before prescribing Imdur, clinicians should evaluate patient-specific factors and monitor for potential complications.

• Assess cardiovascular status: check blood pressure and heart rate prior to initiation.
• Review concomitant nitrate therapy: avoid combined use to prevent severe hypotension.
• Evaluate renal and hepatic function: dose adjustments may be needed in impairment.
• Counsel on orthostatic changes: advise patients to rise slowly from sitting or lying positions.
• Store at ambient temperature: keep below 25°C, retain in original packaging, and protect from moisture.

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

Major Interactions (Avoid)

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

Moderate Interactions (Monitor Closely)

• Antihypertensives (beta‑blockers, ACE inhibitors, diuretics): may enhance blood‑pressure‑lowering effect.
• Alcohol: can increase vasodilatory response and dizziness.
• CYP3A4 inhibitors (e.g., erythromycin, ketoconazole): may raise plasma levels of isosorbide mononitrate.
• Antacids containing aluminum or magnesium: may affect absorption if taken simultaneously.