The pharmacological differences in anti-anginal effects of long-lasting calcium channel blockers: azelnidipine and amlodipine
We examined anti-anginal effects of azelnidipine and amlodipine in an arginine vasopressin (AVP)-induced rat anginal model. Oral administration of azelnidipine or amlodipine produced long-lasting inhibition of AVP-induced ST-segment depression in ECG. The degrees of inhibition with azelnidipine at doses of 1 and 3 mg/kg were comparable to those with amlodipine at 3 and 10 mg/kg. Both drugs lowered mean blood pressure in a dose related manner, while only azelnidipine decreased heart rate. Azelnidipine at 3 mg/kg and amlodipine at 10 mg/kg produced a similar decrease in the rate pressure product, an index for cardiac oxygen consumption. Their inhibitory effects on calcium-induced vascular contraction were compared in isolated porcine coronary arteries. Both drugs produced a slow-developing inhibition of calcium-induced contraction. Although their inhibitory effects were similar, the way the both drugs inhibited calcium-induced contraction differed with each other. After removing the drug from bathing solution, the inhibitory effects of azelnidipine were not blunted but were sustained for a long time which indicates that azelnidipine has high vascular affinity. On the other hand, those of amlodipine were rapidly blunted. These results suggest that the mechanisms underlying anti-anginal effects of azelnidipine differ from those of amlodipine. The anti-anginal effect with azelnidipine may be accounted for by its high affinity to the coronary blood vessels and the heart rate slowing effect, both of which are not shared with amlodipine.