Response of plasma catecholamines and blood pressure to clonidine and to sudden withdrawal of the drug in subjects with essential hypertension.

: In this retrospective study in ten patients with essential hypertension a short-time treatment of 3 days with 0.15 mg clonidine 2 times/day orally, as well as a second short-term treatment period with the slow-release oral preparation (.025 mg clonidine once/day) significantly lowered blood pressure, heart rate, and plasma concentration of norepinephrine in the supine and standing subject. After sudden withdrawal of clonidine all these parameters returned to pretreatment levels within 2-3 days. No rebound or overshoot phenomenon was observed.