Amlodipine works by selectively blocking calcium ions from entering the smooth muscle cells that line your blood vessels and heart. Because calcium causes muscles to contract, blocking it forces the walls of your blood vessels to relax, widen, and dilate. This widening reduces the physical resistance against blood flow, causing blood pressure to drop. This mechanism allows the heart to pump blood throughout the body with far less effort, decreasing its overall oxygen workload. [1, 2, 3, 4, 5]