CARDIOVASCULAR EFFECTS OF BENIDIPINE AND AMLODIPINE IN ISOLATED-TISSUES AND ANESTHETIZED DOGS

Benidipine and amlodipine 1,4-dihydropyridine calcium channel blocking drugs, are long-acting antihypertensive and antianginal drugs. In the present study, the vascular-selectivity and duration of action of ben idipine were determined in vitro and in vivo, and compared with those of amlodipine. The relaxing effect of benidipine on the canine coronar y artery precontracted by KCl (55 mM) was about 30 times that of amlod ipine. The negative inotropic effect of benidipine in the electrically -stimulated canine right ventricular papillary muscle was about twice that of amlodipine. The potency ratios of the vasorelaxing effect in t he coronary artery and the negative inotropic effect in papillary musc le were 1300 for benidipine and 67 for amlodipine, respectively. In an esthetized dogs, the maximum hypotensive effect and the duration of ac tion of 3 mu g/kg (i.v.) benidipine was almost the same as those of 50 0 mu g/kg (i.v.) amlodipine. The duration of the hypotensive action of benidipine at 10 mu g/kg (i.v.) was almost the same as that of amlodi pine at 1500 mu g/kg (i.v.). Amlodipine at 1500 mu g/kg (i.v.) reduced mean blood pressure and left ventricular dp/dt max immediately after its administration, whereas such transient falls were not observed aft er the administration of benidipine at 10 mu g/kg (i.v.). These result s suggest that benidipine possesses a stronger vasodilating effect and a higher vascular-selectivity, compared with amlodipine.