Pharmacodynamics
The principal pharmacological action of nitroglycerin is relaxation of vascular smooth muscle. Although venous
effects predominate, nitroglycerin produces, in a dose-related manner, dilation of both arterial and venous beds.
Dilation of the postcapillary vessels, including large veins, promotes peripheral pooling of blood, decreases
venous return to the heart, and reduces left ventricular end-diastolic pressure (preload). Nitroglycerin also
produces arteriolar relaxation, thereby reducing peripheral vascular resistance and arterial pressure (after load),
and dilates large epicardial coronary arteries; however, the extent to which this latter effect contributes to the
relief of exertional angina is unclear.