Isosorbide Mononitrate Bristol Laboratories (Isosorbide Mononitrate)

Isosorbide Mononitrate belongs to the organic nitrate class and is employed in the management of coronary artery disease‑related chest pain.

• Angina pectoris (stable): reduces the frequency of chest pain episodes.
• Chronic stable angina: improves exercise tolerance and delays onset of symptoms.
• Prevention of angina attacks: maintains consistent nitrate levels to avert sudden episodes.

• After oral absorption, isosorbide mononitrate is metabolized to 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 both preload and afterload, thereby decreasing myocardial oxygen demand and relieving angina.

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: warmth and redness of the face or neck.
• Nausea: mild gastrointestinal upset.
• Palpitations: awareness of heartbeat.
• Hypotension: mild drop in blood pressure.

Serious or Rare Side Effects

• Severe hypotension: marked drop in blood pressure requiring medical attention.
• Syncope: fainting episodes.
• Myocardial infarction: rare but possible in susceptible patients.
• Allergic reaction: rash, itching, or swelling.
• Severe skin reactions: Stevens‑Johnson syndrome or toxic epidermal necrolysis.

Before initiating therapy, clinicians should evaluate patient‑specific risk factors and monitor for adverse events.

• Assess cardiovascular status: check baseline blood pressure and heart rate.
• Avoid concurrent organic nitrates: additive vasodilatory effect may cause profound hypotension.
• Do not combine with phosphodiesterase‑5 inhibitors: risk of severe hypotension.
• Monitor for tolerance development: efficacy may diminish over time.
• Adjust in renal impairment: consider dose modification if renal function is reduced.
• Store at room temperature: keep in the original container, protect from moisture.

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

Major Interactions (Avoid)

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

Moderate Interactions (Monitor Closely)

• Antihypertensive agents: may enhance blood pressure‑lowering effect.
• Diuretics: can increase the likelihood of hypotension.
• Alcohol: may exacerbate dizziness and hypotension.