“The five categories are as follows: (1) musculotropic vasodilators to increase blood flow; (2) alpha-… to improve blood flow; (3) beta-adrenergic activators to augment blood flow; (4) nonadrenergic drugs to retard blood clotting … serotonin, bradykinin, and calcium ions ; and (5) drugs with multiple … involving vascular and nonvascular areas.”