Vascular-selective effect of lercanidipine and other 1,4-dihydropyridines in isolated rabbit tissues

The aim of this study was to characterize the in-vitro vasoselectivity of lercanidipine (in comparison with lacidipine, amlodipine, nitrendipine and felodipine) by evaluating its functional calcium antagonistic activity on rabbit vascular (aorta) and cardiac tissues (heart ventricle). Although incubation with all the compounds tested elicited a concentration-dependent relaxant effect on vascular tissue precontracted with KCl (80 mM), 50% relaxation was reached at different times for each concentration and drug tested. At 10 nM concentration 50% relaxation was reached after 210 min with lercanidipine, 278 min with amlodipine, 135 min with lacidipine, 75 min with nitrendipine and 70 min with felodipine. The onset of the effect was, therefore, similar for lercanidipine, amlodipine and lacidipine, but faster for nitrendipine and felodipine. Similarly, all the compounds tested concentration-dependently reduced the force of cardiac contraction (negative inotropic activity). In this model, the time needed to reach 50% reduction in contractile force was also concentration-dependent, and the ranking order of the speed of onset of the effect (evaluated as the ratio of the IC50 values (the concentrations inhibiting contraction by 50%) calculated after 1 and 4 h incubation) was lacidipine (3.8) > amlodipine (9.6) > felodipine (39) > lercanidipine (68) = nitrendipine (89). The vasoselectivity, expressed as the ratio of the IC50 values obtained on cardiac and vascular tissue, were (for 4 h incubation) 730, 193, 95, 6 and 3 for lercanidipine, lacidipine, amlodipine, felodipine and nitrendipine, respectively, showing that lercanidipine is the most vasoselective of the calcium-antagonists tested. The results show that lercanidipine reduces the inotropic force of the rabbit heart to a lesser extent than do other calcium antagonists, and that this drug had the best heart/vessel selectivity index among the compounds tested at all the times tested.