Studies on the mode of action of hexobendine, a prospective anti‐anginal drug

1 . In cats anaesthetized with pentobarbitone sodium, hexobendine (0.25 mg/kg) markedly increased myocardial blood flow (measured using a heat clearance technique) and usually decreased myocardial metabolic heat production, without influencing cardiac contractility or systemic arterial blood pressure. These effects lasted for about 45 min. 2 . Larger doses (0.5 and 1.0 mg/kg) decreased systemic arterial blood pressure and the rate of rise of the left ventricular pressure pulse (dp/dt), although left ventricular end‐diastolic pressure was usually increased. This is indicative of a decrease in myocardial contractility. 3 . In a concentration of 5 × 10−6g/ml., hexobendine protected isolated rabbit atria against the decrease in contractility that follows the removal of oxygen. 4 . Hexobendine did not antagonize the systemic and myocardial effects of infusions of adrenaline and noradrenaline, nor (except in concentrations of 10−5g/ml.) the increase in contractility induced by these catecholamines on isolated rabbit atria.