Isosorbide Mononitrate Mechanism and Side Effects

Introduction to Isosorbide Mononitrate

The American College of Cardiology states that isosorbide mononitrate is a nitrate vasodilator that works primarily through vasodilation of veins, arteries, and arterioles by promoting the release of nitric oxide, which serves as an exogenous source to replenish or restore the actions of endothelium-derived relaxing factor 1, 2
The primary hemodynamic effects of isosorbide mononitrate include reduction in right and left ventricular preload through peripheral vasodilation, as noted by the American College of Cardiology 1
The American College of Cardiology also reports that isosorbide mononitrate causes afterload reduction resulting from arterial vasodilation 2
Decreased cardiac work and lower myocardial oxygen requirements are additional effects of isosorbide mononitrate, according to the American College of Cardiology 1

The American College of Cardiology and Circulation report that the most commonly reported side effects of isosorbide mononitrate include headaches, the most frequent side effect 3, 4
The American College of Cardiology notes that hypotension is a potentially serious side effect of isosorbide mononitrate, which may result in reflex tachycardia and worsening myocardial ischemia 3
Dizziness related to blood pressure changes is another side effect of isosorbide mononitrate, as reported by Praxis Medical Insights and Circulation 5, 6
The potential for nitrate tolerance with continuous use of isosorbide mononitrate is noted by Circulation and Praxis Medical Insights 6, 5

The American College of Cardiology recommends that isosorbide mononitrate should be used with caution in patients with right ventricular infarction, as these patients are especially dependent on adequate RV preload to maintain cardiac output 3
The American College of Cardiology also advises caution in patients with inferior wall MI with RV involvement, where profound hypotension may occur 3
Isosorbide mononitrate is contraindicated when used with phosphodiesterase inhibitors, such as sildenafil or tadalafil, due to the risk of profound hypotension, as reported by Circulation and Praxis Medical Insights 4, 5

The American College of Cardiology notes that hypotension can be managed by dose adjustment, leg elevation, fluid administration, or atropine if severe 7
Circulation and Praxis Medical Insights report that nitrate tolerance can be minimized by providing a "nitrate-free interval" of at least 10 hours 6, 5

Isosorbide mononitrate has a prolonged duration of action, lasting 12 to 24 hours when used in its standard formulation, according to the American College of Cardiology 8
The American College of Cardiology recommends standard oral isosorbide mononitrate for its duration of effect of 12-24 hours 8

Standard oral isosorbide mononitrate is typically dosed as 20 mg twice daily with effects lasting 12-24 hours, as stated by the American College of Cardiology 8

The American College of Cardiology states that short-acting nitrates include sublingual nitroglycerin tablets with a duration of 1-7 minutes 8
The American College of Cardiology notes that long-acting nitrates include isosorbide mononitrate with a duration of 12-24 hours 8

The American Heart Association, as published in Circulation, recommends a "nitrate-free interval" of at least 10 hours to prevent tolerance development 9
Common side effects of isosorbide mononitrate include headaches and hypotension, similar to other nitrate preparations, according to Circulation 9

Isosorbide mononitrate lowers blood pressure through its vasodilatory effects on both venous and arterial vessels, with the American College of Cardiology noting decreased cardiac work and lower myocardial oxygen requirements resulting from these hemodynamic changes, although the primary therapeutic indication is not for blood pressure management 10
At low doses, isosorbide mononitrate predominantly venodilates, reducing preload and venous return, which indirectly lowers blood pressure, while at higher doses, it also dilates coronary arteries and causes arterial vasodilation, leading to afterload reduction and more direct blood pressure lowering 10

The American Heart Association states that nitrates, including isosorbide mononitrate, have not been shown to be useful for hypertension management, and should not be used to treat hypertension 11, 12
The American Heart Association recommends the use of nitrates, such as isosorbide mononitrate, for angina relief, particularly when β-blockers are contraindicated or cause unacceptable side effects, and for combination therapy with β-blockers for synergistic anti-ischemic effects in angina patients 11, 10