Abstract
The effect of some sympathomimetic amines on the rate of disappearance of22Na injected into the hind legs of rats was studied. The technique used was developed particularly for studying the influence of new drugs on capillary blood flow, i.e. the factor primarily determining drug absorption. Decreased capillary circulation (sodium clearance) in the muscle pocket of the sciatic nerve was produced, in order of efficacy, by adrenaline, noradrenaline, levonordefrin, phenylephrine and metaraminol, in concentrations of 10 and 100 μg/ml. Isoprenaline in low concentration (0.01 μg/ml) was found to enhance capillary circulation.