Isosorbide mononitrate is a long-acting organic nitrate used primarily for the prophylaxis and treatment of angina pectoris. It is a major active metabolite of isosorbide dinitrate. In the Indian context, it is a cornerstone in the management of chronic stable angina, often preferred for its predictable pharmacokinetics and reduced potential for tolerance development compared to other nitrates when dosed appropriately.
Adult: For angina prophylaxis: Initially 20mg twice daily (with a 7-hour interval) or 30-60mg once daily as a sustained-release formulation. The standard 30mg immediate-release tablet is often given as 30mg once in the morning or 20mg twice daily (e.g., 8 AM and 3 PM) to ensure a nitrate-free interval. Dose may be titrated up to 120mg daily in divided doses based on response and tolerance.
Note: Take tablet whole with a glass of water, with or without food. For immediate-release tablets, the twice-daily regimen should have doses spaced 7 hours apart (e.g., 8 AM and 3 PM) to provide a daily nitrate-low period. Do not crush or chew sustained-release formulations. Sit or lie down if feeling dizzy after taking the dose.
Isosorbide mononitrate is a prodrug that is denitrated to release nitric oxide (NO). NO activates intracellular guanylyl cyclase, leading to increased synthesis of cyclic guanosine monophosphate (cGMP). Elevated cGMP causes dephosphorylation of myosin light chains, resulting in smooth muscle relaxation, particularly in venous capacitance vessels, arteries, and coronary vasculature.
Pregnancy: Category C (US FDA). Animal studies show risk; human data insufficient. Use only if potential benefit justifies potential fetal risk. Not recommended during pregnancy unless clearly needed.
Driving: May cause dizziness, lightheadedness, or syncope, especially at initiation. Patients should not drive or operate machinery until their individual response is known and stable.
| Phosphodiesterase-5 Inhibitors (Sildenafil, Tadalafil, Vardenafil) | Profound, life-threatening hypotension | Contraindicated |
| Other Vasodilators (e.g., ACE inhibitors, ARBs, Calcium channel blockers, Alpha-blockers) | Additive hypotensive effect | Major |
| Alcohol | Enhanced vasodilation and hypotension | Major |
| Heparin | Possible decreased anticoagulant effect of heparin | Moderate |
| Dihydroergotamine | May reduce the anti-anginal effect of nitrates and increase ergotamine-induced vasoconstriction | Moderate |
| Antihypertensives | Potentiated hypotension | Moderate |
| Tricyclic Antidepressants (TCAs) | Hypotensive effects may be potentiated | Moderate |
| Riociguat | Hypotensive effects may be potentiated as both increase cGMP | Major |
Same composition (Isosorbide Mononitrate (30mg)), different brands: