Monosan (Isosorbide Mononitrate)

Isosorbide Mononitrate is a nitrate used in the management of coronary artery disease‑related angina.

• Chronic stable angina: reduces the frequency and severity of angina episodes.
• Prevention of angina attacks: maintains stable myocardial oxygen supply during daily activities.
• Exercise‑induced angina: improves exercise tolerance by decreasing cardiac workload.

• Isosorbide Mononitrate is metabolized to release nitric oxide, which activates guanylate cyclase in vascular smooth muscle. The resulting increase in cyclic GMP causes relaxation of arterial and venous walls, producing vasodilation that lowers preload and afterload, thereby improving myocardial oxygen delivery and reducing ischemic symptoms.

Isosorbide Mononitrate may cause a range of adverse reactions. Patients should be aware of both common and serious possibilities.

Common Side Effects

• Headache: mild to moderate, often transient.
• Dizziness or light‑headedness, especially on standing.
• Flushing or warmth sensation on the face and neck.
• Nausea or mild gastrointestinal upset.
• Palpitations or tachycardia.

Serious or Rare Side Effects

• Severe hypotension leading to syncope.
• Allergic reactions such as rash, pruritus, or angioedema.
• Myocardial infarction in patients with unstable coronary disease.
• Stevens‑Johnson syndrome or toxic epidermal necrolysis.
• Life‑threatening arrhythmias (rare).

Before initiating therapy, clinicians should consider several safety measures.

• Blood pressure monitoring: ensure baseline values are stable before use.
• Concomitant nitrates: avoid combined use to prevent excessive hypotension.
• Hepatic impairment: dose adjustment may be required in moderate to severe liver disease.
• Abrupt discontinuation: tapering is recommended to reduce rebound angina.
• Elderly patients: start with the lowest effective dose and monitor closely.
• Store at room temperature: keep in the original container, protect from moisture and direct sunlight.

Isosorbide Mononitrate can interact with several drug classes, requiring careful management.

Major Interactions (Avoid)

• Other nitrates (e.g., nitroglycerin): risk of profound hypotension.
• Phosphodiesterase‑5 inhibitors (e.g., sildenafil, tadalafil): may cause severe blood pressure drops.
• Strong vasodilators (e.g., hydralazine): additive hypotensive effect.

Moderate Interactions (Monitor Closely)

• Antihypertensive agents (beta‑blockers, ACE inhibitors, calcium channel blockers): monitor blood pressure and adjust doses as needed.
• Diuretics: may enhance orthostatic hypotension.
• Alcohol: can potentiate vasodilatory effects and dizziness.
• Smoking: induces tolerance to nitrates, reducing efficacy.