Mechanism of Action and Clinical Effects of Isosorbide Dinitrate

Primary Vascular Effects

Isosorbide dinitrate acts as an endothelium-independent vasodilator that primarily dilates capacitance vessels, increasing venous pooling and decreasing myocardial preload, which reduces left ventricular end-diastolic pressure and pulmonary capillary wedge pressure, according to the American Heart Association 1
Coronary artery dilation also occurs with isosorbide dinitrate, improving oxygen supply to the myocardium, though the relative importance of preload reduction, afterload reduction, and coronary dilation in its therapeutic effect remains undefined, as stated by the American College of Cardiology 1

The American College of Cardiology states that isosorbide dinitrate works by serving as an exogenous source of nitric oxide, replenishing or restoring the actions of endothelium-derived relaxing factor 2

Decreased cardiac work and lower myocardial oxygen requirements result from the combined effects of preload and afterload reduction, as recommended by the American Heart Association 2
The drug reduces right and left ventricular preload through peripheral vasodilation, which is particularly beneficial in conditions where myocardial oxygen demand exceeds supply, according to the European Society of Cardiology 2

The parent compound has a serum half-life of about one hour, but the active metabolites contribute to a duration of action of up to 8 hours with standard oral formulations, as reported by the American College of Clinical Pharmacology 1

Continuous therapy leads to tolerance development, as the anti-anginal efficacy is lost after 24 hours or less of continuous exposure; only after nitrates have been absent from the body for several hours is their efficacy restored, as stated by the American College of Cardiology 1
The three-times-daily dosing regimen naturally provides the necessary nitrate-free interval to prevent tolerance, unlike once-daily or continuous formulations, according to the European Society of Cardiology 3

The American Heart Association suggests that isosorbide dinitrate's arterial effects are more prominent when systemic vascular resistance is severely elevated, with mean arterial blood pressure reductions of 5 to 10 mm Hg persisting for more than four hours following administration 4
The American College of Cardiology recommends a nitrate-free interval of at least 10 hours (and preferably 14 hours for isosorbide dinitrate) to minimize tolerance development, as continuous therapy leads to tolerance development with anti-anginal efficacy lost after 24 hours or less of continuous exposure 4
Combination with ACE inhibitors or hydralazine may help minimize tolerance development, according to the American Heart Association 4

The American Heart Association notes that headaches are the most common side effect of isosorbide dinitrate, resulting from cerebral vasodilation 4