Standards; Isotopic Labeled Analogues; Enzyme Activators and Inhibitors; Pharmaceutical/API Drug Impurities/Metabolites;
Selective inhibitor of phosphodiesterase V (PDE 5); potent coronary vasodilator drug; adenosine transport inhibitor; inhibitor of platelet aggregation.A representative lot was: 36% d20; 25% d19; 13%d18; 24% d17; 1% d16.