Acute vasodilator action of pindolol in humans

The local hemodynamic effect of pindolol, a nonselective beta-blocker with intrinsic sympathomimetic activity, was investigated in 17 healthy volunteers. Changes in forearm blood flow (FBF) in response to infusion of drugs into the brachial artery were measured by plethysmography. Pindolol increased FBF dose dependently to a maximal value of 62 +/- 8% (mean +/- SEM, p less than 0.001) without inducing changes in heart rate or blood pressure. For a single dose of pindolol the maximal effect on FBF was seen after approximately 4 minutes of infusion, and this effect persisted for at least 12 minutes after the infusion. The pindolol-induced increase in FBF was reduced by concomitant infusion of propranolol (p less than 0.001). Intra-arterial infusion of practolol did not influence FBF. No significant influence of pindolol was found on the vasoconstriction induced by the alpha 1-adrenergic receptor agonist methoxamine, the alpha 2-adrenergic receptor agonist BHT-933, or angiotensin II. Measurement of plasma pindolol concentrations in the venous effluent of the forearm suggested that vasodilatation occurred at drug levels within the therapeutic range. These results indicate that the beta-blocker pindolol has vasodilatory properties owing to stimulation of vascular beta 2-adrenergic receptors and that this effect may be of therapeutic relevance.