Dose-response relationship of single oral doses of guanabenz in hypertensive patients

A single-blind, placebo-controlled study was conducted to determine the dose-response relationship of guanabenz, administered as single oral doses to patients with mild or moderate hypertension. Twelve hypertensive patients received ascending oral doses of 2, 4, 8, 16, 24, and 32 mg of guanabenz. Dose-response relationships were evaluated for the nine patients who received placebo and all six guanabenz doses. The greatest maximum response (40/24 mm Hg) was seen for the 16 mg guanabenz dose. Since eight of the nine patients had mild hypertension, they may have responded maximally to the lower guanabenz doses, precluding larger decreases with the 24 and 32 mg doses. The mean onset of satisfactory blood pressure reduction decreased from 4 to 2 h and the mean duration increased from 6 to 22 h as the oral dose was increased from 2 to 32 mg. In eight patients, the responses to 16 mg of guanabenz administered sublingually and orally were compared. The sublingual and oral routes produced similar mean (20/13 mm Hg) and maximum (33/24 mm Hg) blood pressure decreases as well as mean onset (2 h) and duration (16.5 h) of satisfactory response. Additional studies involving patients with more severe hypertension are needed to further characterize the dose-response relationship of oral guanabenz and to establish a dose-response relationship for sublingual guanabenz.