In-vitro study of the effect of clentiazem on rabbit aorta and on myocardium.

We evaluated the pharmacologic action of clentiazem, a newly synthesized diltiazem derivative, on isolated rabbit aorta and myocardium. In addition to its Ca2+ blocking action, clentiazem demonstrated both vasorelaxing and negative inotropic actions similar to diltiazem. The vasorelaxant action of clentiazem on the tonic phase of KCl-induced contraction (EC50 = 6.13 x 10(-8) M) was 4.5 times more potent than diltiazem (EC50 = 2.77 x 10(-7) M). However, the negative inotropic action of clentiazem (IC50 = 4.34 x 10(-5) M) was similar to diltiazem (IC50 = 3.94 x 10(-5) M). Selectivity ratios, comparing the effectiveness in cardiac muscle with aorta, were clentiazem (708) greater than diltiazem (142). In conclusion, clentiazem is a Ca2+ antagonist and demonstrates greater vasoselectivity than diltiazem. It also has a longer lasting action than diltiazem.