The Pressor Response to Water Drinking in Humans

Water drinking significantly and rapidly raises sympathetic activity. Indeed, it raises plasma norepinephrine as much as such classic sympathetic stimuli as caffeine and nicotine. This effect profoundly increases blood pressure in autonomic failure patients, and this effect can be exploited to improve symptoms due to orthostatic hypotension. Water drinking also acutely raises blood pressure in older normal subjects. The pressor effect of oral water is an important yet unrecognized confounding factor in clinical studies of pressor agents and antihypertensive medications.