The effects of LU49700 (CAS 116759-60-5), the main metabolite of gallopamil (CAS 16662-47-8) on the mechanical response of isolated rat aortic and guinea-pig ventricular papillary muscle preparations were compared with those of gallopamil. Gallopamil and LU49700 inhibited the 64 mmol/l KCl-induced contraction of rat aorta in a concentration-dependent manner. The vasorelaxant potency of LU49700 was 244 times weaker than that of gallopamil. Gallopamil and LU49700 produced concentration-dependent negative inotropic effects on isolated right ventricular papillary muscles. The negative inotropic potency of LU49700 was 418 times weaker than that of gallopamil. These findings indicate that LU49700 has a weaker cardiovascular depressant potency than gallopamil. Therefore, LU49700 may not mediate the effects of gallopamil for treating subjects with cardiovascular diseases.