Effects of felodipine on vascular smooth muscle in comparison with nifedipine

Felodipine (ethylmethyl 4-(2,3-dichlorophenyl)-1,4-dihydro-2,6-dimethyl- 3,5-pyridine dicarboxylate, CAS 72509-76-3), a vasoselective calcium antagonist, has a slow onset inhibitory effect on high K(+)-induced contractions in vascular smooth muscle and a longer duration than that of nifedipine. In addition it non-competitively inhibits Ca(++)-induced contraction in the depolarized aorta or femoral artery in the rat. Felodipine's inhibitory effect on caffeine or norepinephrine-induced contraction was observed at a micromolar range. This result suggests that felodipine may inhibity Ca++ release from intracellular Ca++ stores through a mechanism of Ca++ or inositol 1,4,5-triphosphate induced Ca++ release in addition to a blockade of Ca++ influx through the sarcolemma.