Amlodipine high blood pressure drug, molecular model. This drug, marketed as Istin, is used to treat hypertension (high blood pressure) and angina pectoris (heart pain). It is a calcium channel blocker, which prevent calcium ions from entering muscle cells when excited, leading to weaker muscle contraction. This dilates blood vessels and reduces the force of contraction of the heart. In this molecule, atoms are shown as spheres and are colour coded: carbon is yellow, oxygen is red, hydrogen is white, nitrogen is blue and chlorine is green.