EFFECT OF M-NIFEDIPINE, A CALCIUM ANTAGONIST, ON CARDIAC PERFORMANCE AND OXYGEN CONSUMPTION IN ANESTHETIZED ANIMAL: A COMPARISON WITH NIFEDIPINE

Meta-nifedipine(m-nif) is a calcium antagonist synthesized by Tianjin Institute of Pharmaceutical Industry. The effects of m-nif on cardiac output(CO), cardiac index(CI), stroke index(SI) were monitored in 6 anesthetized close chest dogs by impedence cardiographic method in comparison with nifedipine(nif). The magnitude of increase of CI and SI by m-nif was more than those of nif for 2. 7-and 4-fold, respectively, at the same dose(20 μg/kg ⅳ). The duration of action of m-nif was also longer than that of nif. m-nif produced a marked reduction of the peripheral vasocular resistance. In addition, the pulse pressure was increased because the decrease of diastolic blood pressure was much larger than that of the systolic. In concomitance with its effect in improving cardiac performance, m-nif caused a slight slowing of heart rate(HR). However, nif increased HR.Tension-time index(TTI), as cardiac energy and oxygen consumption index, was decreased significantly by m-nif more than by nif in cats. m-Nif raised oxygen content in the coronary sinus blood and reduced oxygen difference between arterialand coronary sinus blood. The rate of oxygen uptake and the rate of CO₂ production were reduced to a greater degree with m-nif. It appears that effects of m-nif in improving the left ventricular pump function, myocardial oxygen consumption, CO₂ production and reducing peripheral vasocular resistance were stronger and lasted longer than those of nif. Thus, m-nif seems to have more beneficial effects in treatment of congestive heart failure.