Some pharmacological properties of organic nitrates.

The organic nitrates exert the same pharmacological actions. They differ in potency and in pharmacokinetics. They are more potent as dilators of veins than of arteries/arterioles and more potent as dilators of large arteries than of arterioles. This hemodynamic profile decreases heart work mainly by preload reduction but to some extent also by afterload reduction. The coronary flow is relatively improved and a redistribution to the ischemic myocardium takes place. The nitrates may facilitate the dissociation of oxygen from oxyhemoglobin and also may cause a more efficient energy metabolism. The basal mechanisms of action involve-SH groups and consecutively cyclic GMP. Glyceryl trinitrate is denitrated faster by the liver than is isosorbide dinitrate. The first pass metabolism is easily circumvented by sublingual and dermal application. Oral administration requires large dosages. Metabolites may contribute to the pharmacological activity. Plasma concentrations cannot be used to predict clinical effects of the nitrates.