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

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Abstract
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=6.13×10−8 M) was 4.5 times more potent than diltiazem (EC50=2.77×10−7 M). However, the negative inotropic action of clentiazem (IC50=4.34×10−5 M) was similar to diltiazem (IC50=3.94×10−5 M). Selectivity ratios, comparing the effectiveness in cardiac muscle with aorta, were clentiazem (708) > diltiazem (142). In conclusion, clentiazem is a Ca2+ antagonist and demonstrates greater vasoselectivity than diltiazem. It also has a longer lasting action than diltiazem.