MYOCARDIAL AND VASCULAR EFFECTS OF EFONIDIPINE IN-VITRO AS COMPARED WITH NIFEDIPINE, VERAPAMIL AND DILTIAZEM

1. Effects of efonidipine on isolated myocardial and aortic preparatio ns were compared with those of nifedipine, verapamil and diltiazem. 2. All drugs produced concentration dependent negative chronotropic effe cts on isolated guinea pig atrial preparations, The potency order was efonidipine greater than or equal to nifedipine>diltiazem greater than or equal to verapamil, EC(30) values being 3.08 x 10(-8)M, 3.48 x 10( -8)M, 1.27 x 10(-7)M and 1.47 x 10(-7)M, respectively. 3. Nifedipine, verapamil and diltiazem produced concentration dependent negative inot ropic effects on isolated guinea pig left atrial preparations. The pot ency order was nifedipine > verapamil) diltiazem, EC(30) values being 4.94 x 10(-8)M, 1.49 x 10(-7)M and 8.03 x 10(-7)M, respectively. Efoni dipine, even at 1 mu M produced no inotropic effect: 10 mu M efonidipi ne decreased the contractile force by about 20%. 4. All drugs concentr ation dependently attenuated the KCl-induced contraction of isolated r at aortic ring preparation. The potency order was nifedipine>efonidipi ne>verapamil>diltiazem, EC(30) values being 2.98 x 10(-9)M, 1.24 x 10( -8)M, 3.96 x 10(-8)M and 2.13 x 10(-7)M, respectively. 5. Thus, efonid ipine was demonstrated to be a potent vasodilator with negative chrono tropic but minimal negative inotropic activity, which may be of benefi t in the treatment of cardiovascular disorders.