Bethanidine dose, plasma levels, and antihypertensive effects.

Bethanidine dose, plasma levels, and hypotensive effects were evaluated in twelve hypertensive patients. Diuretic therapy with benzthiazide was started two weeks before and continued during the study. Bethanidine was given three times daily. After two to 12 months of therapy in 11 of the patients, the mean standing diastolic pressure was reduced from 112 to 91 mm Hg. The mean total daily bethanidine dose was 79 mg (range 30--150 mg). The mean plasma bethanidine was 0.65 micrometer (range 0.1--2.8 micrometer), which correlated with the bethanidine dose. There was less correlation between dose and antihypertensive effect. The effects of sudden withdrawal from chronic bethanidine dosing were observed in six patients. The orthostatic effect of bethanidine was lost within 12 hours, but the half-time of elimination of bethanidine from plasma was 39 hours. Based upon the present findings, recommendations are presented for initiation and maintenance of antihypertensive therapy with bethanidine.