Background and objective Although there is concern that cibenzoline, an antidysrhythmic drug for the treatment of ventricular and supraventricular dysrhy-thmias, may be associated with dose-dependent inhibition of myocardial contractility there are few reports about the relationship between myocardial metabolism and cardiac function when it is used. The present study was designed to investigate the effects of cibenzoline on cardiac function and metabolism. The effects of cibenzoline on cardiac function and myocardial metabolism were assessed in the isolated rat heart-lung preparation.

Methods Thirty-two male Wistar-ST rats were divided into four groups: control, and those to receive cibenzoline, either 300, 900 or 3000 ngmL−1. The cibenzoline was administered into the perfusate 5min after the start of perfusion. Heart rates in the 3000ngmL−1 group were significantly lower than those in the control group. Cardiac output in the 3000 ng mL−1 group at 15 and 30 min was significantly lower than in the control group. In all groups, values for %LV dP/df max (the ratio of values at each time to those at 5 min) at 20, 25, 30 min were significantly higher than at 5min. Myocardial adenosine tripho-sphate concentration in the 3000ngmL−1 group was significantly lower than in controls. There was no difference between groups in the lactate/pyruvate ratio.

Conclusion The therapeutic range of cibenzoline has few effects on cardiac function and metabolism, although concentrations 10 times greater may cause a deterioration in myocardial metabolism.