Introduced respectively by Brunton in 1867 and Murrell in 1879, amyl nitrite inhalations and nitroglycerin "sub-linguations" appeared to be so effective in alleviating anginal pain that they were often used as diagnostic tests for myocardial ischemia. As contrasted with noncoronary pain, that of "true" angina was expected to respond to either amyl nitrite or nitroglycerin—both drugs having been assumed to differ from each other only in their side effects.
These simplistic presuppositions of predictable effectiveness of these drugs and uniformity of their actions are no longer tenable. Increasing knowledge of the hemodynamics of angina and the pharmacodynamics of nitrites is providing new insights into the intricacies of their interrelationships.
Because both amyl nitrite and nitroglycerin are primarily smooth muscle relaxants, and thus vasodilators, their initial effect is that of arteriolar and venous dilation—the former resulting in diminished venous return to the heart, the latter in decreased resistance to left ventricular