Clinical investigation of an antagonist at α‐ and β‐adrenoceptors‐AH 5158A

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Abstract
1 The α- and β-adrenoceptor blocking action of AH 5158A was investigated in man using the veins of the hand, the arterial bed of the forearm, and certain responses of the circulation as a whole. 2 In the veins, locally infused AH 5158A resulted in specific and competitive antagonism of the constrictor response to locally infused noradrenaline and of the dilator response to isoprenaline. 3 Brachial artery infusions of AH 5158A resulted in competitive antagonism of the arterial blood flow changes produced by local infusions of noradrenaline and isoprenaline. 4 Systemic infusion of AH 5158A (0·5–0·9 mg/kg) produced clear blockade of the heart rate response to systemic infusion of isoprenaline. It also attenuated the response to exercise at 80 watts for 4 min; mean arterial pressure during exercise was reduced by 16% and heart rate by 18%. Blockade lasted at least 1 hour. 5 AH 5158A caused small changes in arterial pressure and heart rate at rest supine, but had no effect on the response of pressure and rate to tilting.