Isomonat (Isosorbide Mononitrate)

Isosorbide Mononitrate is used in the management of coronary artery disease, specifically to treat angina pectoris.

• Angina pectoris: reduces the frequency and severity of chest pain episodes by dilating coronary vessels.
• Chronic stable angina: improves exercise tolerance and decreases myocardial oxygen demand.
• Exercise‑induced angina: prevents pain during physical activity by maintaining adequate coronary blood flow.

• After oral absorption, isosorbide mononitrate is metabolized to nitric oxide, which activates guanylate cyclase in vascular smooth muscle. The resulting increase in cyclic GMP leads to relaxation of smooth muscle, vasodilation of both veins and arteries, reduced preload and afterload, and consequently lower myocardial oxygen consumption.

Isomonat may cause a range of adverse reactions, most of which are mild and transient.

Common Side Effects

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

Serious or Rare Side Effects

• Severe hypotension: marked drop in blood pressure that may cause fainting.
• Syncope: sudden loss of consciousness due to inadequate cerebral perfusion.
• Allergic reactions: rash, itching, swelling, or rare anaphylaxis.
• Myocardial infarction (rare): chest pain not relieved by the medication.

Before initiating therapy, clinicians should evaluate cardiovascular status and consider potential risks.

• Blood pressure monitoring: check baseline and periodic readings to avoid excessive hypotension.
• Avoid abrupt discontinuation: tapering may be required to prevent rebound angina.
• Hepatic impairment: use with caution as metabolism may be altered.
• Concomitant PDE5 inhibitors: increased risk of severe hypotension; avoid co‑administration.
• Store at room temperature: keep in the original container, protect from moisture and direct sunlight.

Isomonat can interact with several drug classes, requiring attention to dosing and monitoring.

Major Interactions (Avoid)

• Other organic nitrates (e.g., nitroglycerin): additive vasodilatory effect may cause profound hypotension.
• Phosphodiesterase‑5 inhibitors (e.g., sildenafil): risk of severe blood pressure fall.
• Strong antihypertensives: may lead to excessive blood pressure reduction.

Moderate Interactions (Monitor Closely)

• Azithromycin: may increase nitrate plasma concentrations.
• Rifampin: may reduce effectiveness by inducing hepatic metabolism.
• Diuretics: can enhance hypotensive response, requiring blood pressure surveillance.