The 3 main classes of antianginal drugs are nitrates, beta blockers, and calcium channel blockers. Nitrates have been viewed classically as affecting myocardial demand by reducing intraventricular volume and lowering the filling pressure of the left ventricle. They have been used increasingly to improve oxygen supply in myocardial ischemia by increasing coronary blood flow and actually causing coronary vasodilatation, and by having an effect on endothelial competence. Beta blockers are used to decrease myocardial blood flow by reducing myocardial demand, with reduction of myocardial contractility, afterload, and heart rate. No major improvement of oxygen supply is seen with this class of medication, and in fact, there is some potential for augmenting coronary vasoconstriction. Calcium channel blockers not only reduce myocardial demand by reducing afterload and, in some cases, heart rate, but similar to nitrates, they enhance myocardial oxygen supply.