Amlodipine has high selectivity and affinity for calium channels in the periphery. Thus, it mainly affects the smooth muscle of blood vessels. There it binds to calcium channels and blocks them. As a result, calcium ions can no longer flow in and a contraction is prevented, because calcium is essential for the transmission of stimuli and the subsequent contraction of the muscle fibers. The block causes the blood vessels to dilate, resulting in a reduction in blood pressure.
Amlodipine is absorbed very slowly but almost entirely in the gastrointestinal tract. Because of the slow absorption, peak concentrations in blood plasma are reached only after 6-12 hours. The bioavailability of amlodipine is between 64-90%. Plasma protein binding is about 94% and the plasma half-life is very high at about 30-50 hours. This high half-life makes amlodipine particularly attractive as a drug, as it means it only needs to be taken once a day. A major part of the dose is broken down by the liver and subsequently excreted in the urine.
Amlodipine should not be taken together with drugs which inhibit enzymes of CYP 450 family. Furthermore it should not be taken concomitantly with diltiazem and clarithromycin.
Amolidpine itself may increase the plasma concentrations of simvastatin, tacrolimus and cylcosporine. Therefore, they should not be taken together.