Previous studies provide conflicting conclusions concerning the consequences of abrupt withdrawal of
guanabenz therapy for
essential hypertension. In the present study, 10 patients were treated for mild to moderate
essential hypertension for 12 weeks, following which the
drug was abruptly withdrawn. Blood pressure, pulse rate, and plasma
catecholamine levels were obtained before, at 4 and 12 weeks after starting
therapy, and 48-96 h and 4 and 8 weeks post-
therapy. At the end of 12 weeks of
therapy, the mean dose of
guanabenz was 22.2 +/- 4.4 mg/day (range, 16-48 mg/day) and supine blood pressure was 140 +/- 5.5/88 +/- 2.4 mm Hg. Two to 4 days after
drug withdrawal, supine and standing diastolic blood pressure remained significantly reduced compared to control (p less than 0.01). Standing systolic blood pressure also remained significantly reduced compared to control (p less than 0.01). Mean plasma
catecholamine level was less than baseline after 4 weeks of
therapy, but the change was not significant. No increase in plasma
catecholamine concentration was observed at any time during the withdrawal period. No patient had symptoms of sweating, nervousness, palpitations, or
insomnia after
guanabenz withdrawal. In one patient with pretreatment systolic pressure of 150 mm Hg, systolic pressure 48 h after
drug withdrawal was 160 mm Hg. These studies, together with previous reports, suggest that
guanabenz therapy for mild to moderate
essential hypertension in doses of 32 mg/day or less can be safely withdrawn on an outpatient basis with a very low incidence of withdrawal phenomena.