orthostatic hypotension
a drop in blood pressure when moving from a lying or sitting position to a standing position. Blood pressure is normally maintained during changes in position by activation of baroreceptors in the walls of the heart and the major arteries. Activation of these receptors in turn activates alpha-adrenergic receptors in peripheral blood vessels, leading to arterial constriction and maintenance of blood pressure. Numerous psychotropic drugs (e.g., antidepressants, antipsychotics) block the activity of peripheral alpha-adrenergic receptors, leading to orthostatic hypotension and an increased risk of falls, particularly in older adults. Orthostatic hypotension can also be caused by such disorders as diabetes mellitus, amyloidosis, and Parkinson’s disease. Also called postural hypotension.