Effect of antihypertensive therapy on sympathetic nervous system activity in patients with essential hypertension.

The sympathetic nervous system (SNS) plays a major role in blood pressure regulation. Although the exact relationship of the SNS to the etiology of hypertension remains undetermined, many of the agents used to treat hypertension interfere with this system. Clonidine, methyldopa, guanethidine, and reserpine decrease SNS tone whereas hydralazine, minoxidil, and hydrochlorothiazide increase it. Most evidence suggests that beta-adrenergic blocking agents decrease SNS activity. The effect of prazosin and captopril on the SNS requires further study. The appropriate use of these antihypertensive agents requires a knowledge of their sites of action and the physiological reflexes they induce. Efficacy, toxicity, and effective drug combinations can be predicted based on their mechanism of action and effect on SNS activity.