Verapamil is a L-type Calcium channel blocker. It has both peripheral and coronary vasodilator effects (IC50 = 0.38 μM in guinea pig aortic strip) and has been used to control hypertension, angina, cardiac arrhythmia, and vascular headaches. Verapamil also acts as an inhibitor of drug efflux pump proteins such as P-glycoprotein, which are often over-expressed in certain tumor cell line. MW: 491.07. Purity ≥98% by HPLC