Nitrate patches: duration of action and loss of efficacy. Reflections on the nitrates' mode of action.

Nitroglycerin patches deliver 0.003 mg nitroglycerin per minute through the skin. This small dose led to an antianginal effect in the short term and when applied with a nitrate pause at night also during sustained use. Minimal doses of i.v. nitroglycerin (0.025 mg) do have antianginal activity. This dose has no effect on pre- and afterload, but increases the diameter at the point of the stenosis. These findings are in accordance with newly won insights into the mode of action of nitrate in coronary heart disease. In the area of the stenosis EDRF cannot be produced by the intima because of damage resulting from arteriosclerotic plaques. EDRF is identical with NO. Thus, the administration of low doses of nitrates that act by means of the NO radical can increase the diameter in the stenosis, since the physiological dilator (EDRF) is no longer present. The increased flow caused by dilatation is the main factor in the antianginal activity of nitrates.