Effect of dichloroisoprenaline on the peripheral vascular responses to adrenaline in man.

In suitable doses dichloroisoprenaline blocks the initial transient vasodilatation, but leaves unchanged the subsequent vasoconstriction, normally seen during intra-arterial infusion of adrenaline to the human forearm. Dichloroisoprenaline blocks both the initial transient large vasodilatation, and the subsequent sustained modest vasodilatation, normally seen in the forearm when adrenaline is infused intravenously. Dichloroisoprenaline abolishes the dilator effects of intra-arterial isoprenaline. These findings are consistent with the hypothesis that the difference between the responses to intra-arterial and intravenous adrenaline is due to the conversion in the body, elsewhere than in the forearm, of adrenaline to an isoprenaline-like substance.