<prompt> All of the following statements about antianginal action of nitrates are true except?Myocardial O2 consumptionBoth pre and after loadTotal coronary flowCause ourable redistribution of coronary flow  <response>: Ans. is c i.e., Total coronary flow Pharmacological actions of nitrates The only major action is direct nonspecific smooth muscle relaxation. The most prominant action is exeed on vascular smooth muscles. Preload reduction - Nitrates dilate veins more than aeries decreased venous return preload - decreased end diastolic size and pressure - decreased O2 consumption. Afterload reduction - Nitrates also produce some aeriolar dilatation - slightly decreased total peripheral resistance afterload. Redistribution of coronary flow. Other smooth muscles - Nitrates cause relaxation of bronchi, biliary tract, esophagus - can be used in biliary colic and esophageal spasm. 