Vascular and myocardial effects of amlodipine: an overview

Amlodipine is a long-acting dihydropyridine calcium antagonist with vascular selectivity. Although structurally related to nifedipine, amlodipine differs in several important respects, including its slow rate of onset and slow recovery. These effects probably reflect the relatively slow rate of association and dissociation of amlodipine with its binding site. The interaction of amlodipine with the calcium antagonist binding site associated with the slow Ca2+ channels differs from that of other dihydropyridines in that it involves the binding domains for the phenylalkylamine- and benzothiazepine-based antagonists, as well as for the dihydropyridines. The prolonged duration of action of amlodipine makes it suitable for use in conditions where calcium channel blockade is required on a 24-h basis. To determine whether amlodipine has a vascular protective effect, amlodipine was given orally to either cholesterol-fed rabbits or stroke-prone hypertensive rats. In the cholesterol-fed rabbits amlodipine (1 or 5 mg/kg/day) produced a significant, dose-dependent reduction in the incidence of atheromatous lesions in the thoracic aorta over an 8-week period. In stroke-prone rats the administration of amlodipine at a dose of 5 mg/kg/day reduced the incidence of mortality over a 30-week treatment period. In spontaneously hypertensive rats amlodipine (5 mg/kg/day) caused a fall in systolic blood pressure, accompanied by a significant (P less than 0.01) reduction in cardiac hypertrophy. When administered intravenously (0.25 mg/kg) 5 h before hearts were excised and made globally ischaemic for short periods (the 'stunned' heart) amlodipine pretreatment improved functional recovery associated with reperfusion.