[Comparable ergometric examinations before and after administration of practolol and bunitrolol (author's transl)]

By means of a standardized, single-level ergometric load of 1.5 watt/kg body weight, the effects of a new beta-adrenergic receptor blocking agent bunitrolol (o-(2-hydroxy-3-tertiary butylamino)-propoxy)-benzonitrile) was compared with the well-known cardiovascular properties of practolol during an intraindividual therapeutic crossover trial after intravenous administration. In the absence of any side-effects, bunitrolol shows a higher degree of beta-adrenergic receptor bocking activity than practolol, with a distinct specificity towards myocardial receptors and very low cardiodepressive properties at rest. Bunitrolol caused a marked reduction (33%) in exercise-induced myocardial work effort, whilst practolol achieved a reduction of only 17% under equal conditions. Thus, the same physical work load is performed after bunitrolol more economically by decreasing both heart rate and blood pressure. The circulatory effects of an intravenous dose of 5 mg bunitrolol seems to be twice as effective as 10 mg practolol. This implies that beta-adrenergic receptor blockade by bunitrolol during work performance is four times as effective as practolol. The observed marked effect of bunitrolol on the diastolic blood pressure is discussed.