Nitroglycerin stability: effects on bioavailability, assay and biological distribution.

The solution, absorptive, and adsorptive properties of nitroglycerin are related to problems encountered in the intravenous use of solutions of the drug and in its assay in biological tissues. Solutions of the drug in usual intravenous fluids are quite stable to hydrolysis under neutral conditions. Loss to plastic intravenous delivery set components by rapid adsorption and slower absorption processes present a significant clinical problem. Assay of the drug and its major metabolites is complicated by problems of extraction related to the solubility of nitroglycerin, its metabolites and substances in the plasma. Loss of nitroglycerin incubated with red blood cells is a very rapid process (half-life 4.0 min. at 10 ng/ml). The mechanism appears to be a physical process rather than an enzymatic one. The loss to blood cells and perhaps other biological materials should be considered in an analysis of the distribution of the drug.