Summary:

The class of drugs called nitrates includes medications that are known to cause the formation and/or release of nitric oxide in the smooth muscle lining of blood vessels, thereby causing smooth muscle relaxation and vasodilatation.  Medications in this drug class include nitroglycerin, isosorbide dinitrate (ISDN, Isordil), and isosorbide mononitrate (which was previously marketed as Imdur).

Nitroglycerin's (as well as isosorbide dinitrate's) ability to improve myocardial oxygen demand has been shown to be from:

• A reduction in mean blood pressure (on average is about 13 mm Hg)
• Shorter ejection time (average 0.04 sec)
• Reduction in preload that decreases end diastolic volumes and ventricular wall size
  
• Redistribution of blood flow to the subendocardium of ischemic areas while maintaining flow in normal areas

The net improvement myocardial oxygen demand occurs despite an average increase in the pulse by 10 bpm.  When the National Heart and Lung Institute studied nitroglycerin in adults with stable angina undergoing exercise stress testing, nitroglycerin was shown to improve exercise capacity and delay the time of onset of ischemic electrocardiographic changes.  This study included both an evaluation of nitroglycerin and isosorbide dinitrate.

Author: Anthony J. Busti, MD, PharmD, FNLA, FAHA
Editor:  Dylan Kellogg, MD
Last Reviewed:  August 2015