Hemodynamic and humoral effects of coffee after β1-selective and nonselective β-blockade

Abstract

A substantial rise in plasma catecholamines occurs after caffeine. Epinephrine infusion induces a pressor response after nonselective .beta.-blockade. The hemodynamic and humoral effects of drinking coffee after placebo and after both nonselective (propranolol) and .beta.1-selective (metoprolol) blockade in 12 normotensive subjects were studied. After placebo, coffee induced a rise in systolic and diastolic blood pressure, and a fall in heart rate, whereas forearm blood flow did not change. Plasma catecholamines, especially epinephrine (+150%), rose and plasma renin activity fell after drinking coffee. The effects of coffee on blood pressure, forearm blood flow and all humoral parameters were not altered by pretreatment with propranolol or metoprolol. The fall in heart rate after coffee seemed to be greater during propranolol. The rise in plasma epinephrine after coffee was evidently too small to reveal differences in reaction in propranolol- and metoprolol-pretreated subjects.