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.