Amlodipine is a 1,4-dihydropyridine calcium antagonist which, although structurally related to nifedipine, has a number of important distinguishing properties. A high oral bioavailability of amlodipine has been demonstrated in a number of animal species and man, together with a long elimination half-life. In vitro studies have demonstrated a slow onset of action which is consistent with the findings from receptor binding studies which show that amlodipine binds to receptor sites with slow rates of association and dissociation. These studies have also shown that amlodipine may interact with both dihydropyridine and diltiazem binding sites. In vivo animal experiments have confirmed the gradual onset of action observed in vitro and have shown amlodipine to have sustained antihypertensive effects with no change in heart rate. Amlodipine has also been shown to attenuate the cardiac hypertrophy associated with the development of hypertension in spontaneously hypertensive rats. Animal studies have clearly demonstrated the mild natriuretic and diuretic properties of amlodipine. The pharmacodynamic and pharmacokinetic properties of amlodipine make this drug an optimal choice of treatment for the control of hypertension with once daily administration.