Clonidine, a centrally acting sympathetic inhibitor, as monotherapy for mild to moderate hypertension.

Sixteen patients with uncomplicated essential hypertension were treated with 0.2 mg of clonidine three times daily as the sole antihypertensive drug. Blood pressure decreased from 167 +/- 4/105 +/- 2 to 139 +/- 3/89 +/- 2 mm Hg (mean +/- standard error of the mean) after 1 week (p less than 0.001) and remained at 140 +/- 3/90 +/- 2 mm Hg after 3 months of therapy. There were no significant changes in cardiac output, blood volume, renal blood flow or glomerular filtration rate during clonidine therapy. Clonidine significantly decreased plasma catecholamines and there was a linear correlation between the change in blood pressure and decreases in plasma catecholamine concentration (r = 0.61, p less than 0.001). There was also a significant correlation between the decreases in heart rate and blood pressure (r = 0.78, p less than 0.001). It is concluded that clonidine can be used effectively and safely as the sole agent in the treatment of mild to moderate hypertension.