[Effect of M-nifedipine and metoprolol in combination on the hemodynamics in rabbits]

Hemodynamic effects of m--nifedipine (m--Nif) combined with metoprolol (Met) were studied in conscious rabbits with impedance cardiography. Administration of m--Nif by intravenous injection (20 micrograms/kg) or by intraduodenal route (0.25 mg/kg) increased cardiac index (CI) and reduced total peripheral resistance (TPR) and arterial pressure. Intravenous injection of Met significantly slowed heart rate without great change in other hemodynamic parameters in conscious rabbits. Combination of m--Nif with Met gained the advantages of both m--Nif and Met. The negative effects of Met on CI and TPR were balanced by the vasodilatory effect of m--Nif. The difference between the results of m--Nif combined with equal dose of Met or with five times the dose of Met was just that further decrease of heart rate was observed. These results suggest that combined administration of m--Nif with Met may be more beneficial than giving each drug alone. It may be more suitable to use m--Nif combined with low doses of Met in order to avoid the danger of depressing myocardium.