A multicenter, randomized, double-blind dose-response evaluation of step-2 guanfacine versus placebo in mild to moderate hypertension

Centrally acting antihypertensive agents: an update

Centrally acting agents stimulate alpha(2) receptors and/or imadozoline receptors on adrenergic neurons situated within the rostral ventrolateral medulla and, in so doing, sympathetic outflow is reduced. Centrally acting agents also stimulate peripheral alpha(2) receptors, which, for the most part, is of marginal clinical significance. Central a agonists have had a lengthy history of use, starting with alpha-methyldopa, which has had a dramatic decline in use, in part, because of bothersome side effects. Patients who require multidrug therapy with otherwise resistant hypertension, such as diabetic and/or renal failure patients, are typically responsive to these drugs, as are patients with sympathetically driven forms of hypertension. Perioperative forms of hypertension respond well to clonidine, a circumstance where the additional anesthesia- and analgesia-sparing effects of this drug may offer additional clinical benefits. Clonidine can be used adjunctively with other more traditional therapies in heart failure, particularly when hypertension is present. Sustained-release moxonidine, however, is associated with early mortality and morbidity when used in patients with heart failure. Escalating doses of drugs in this class often give rise to salt and water retention, in which case diuretic therapy becomes a valuable adjunctive therapy.

Antihypertensive efficacy of guanfacine and methyldopa in patients with mild to moderate essential hypertension

Guanfacine, an alpha-2 adrenoceptor agonist, was compared with methyldopa as step-2 therapy for patients with mild-to-moderate essential hypertension in a 12-week, double-blind, randomized, parallel evaluation of efficacy and safety. The study consisted of a 2-week screening/weaning period (phase I), a 3-week treatment period with a diuretic (phase II), and a 12-week treatment period with a diuretic plus methyldopa or guanfacine (phase III). Patients were weaned from prior anti-hypertensive medication during the screening/weaning period and began receiving chlorthalidone 25 mg every morning. Patients received only 25 mg of chlorthalidone each morning during the phase II period. Those who had an average seated diastolic blood pressure (BP) of 95-114 mm Hg at the end of the phase II period were eligible to enter the phase III period and were randomly assigned to chlorthalidone plus guanfacine, 1 mg every night, or methyldopa, 250 mg tid. Seated and standing systolic and diastolic BP and pulses were measured biweekly for 12 weeks after randomization. Of the 112 patients who were randomly assigned to guanfacine or methyldopa, 87% completed the entire study. The mean seated systolic and diastolic BP were reduced 13/13 mm Hg by guanfacine administration and 15/13 mm Hg by methyldopa administration. No significant changes in seated pulse were seen in either group. Similar changes occurred in the standing position. Very few adverse effects were reported during the study, the most prevalent side effect was xerostomia (13% guanfacine, 9% methyldopa). No significant differences were observed between treatment groups for the incidence of cardiac arrhythmias after methyldopa or guanfacine administration was stopped.(ABSTRACT TRUNCATED AT 250 WORDS)

Antihypertensive efficacy of guanfacine and prazosin in patients with mild to moderate essential hypertension

Guanfacine, an alpha 2 adrenoceptor agonist, was compared with prazosin hydrochloride for the treatment of patients with mild to moderate essential hypertension in an 8-week, double-blind, randomized, parallel evaluation to determine efficacy and safety. The study consisted of a 2-week screening/weaning period (phase I), a 3-week treatment period with chlorthalidone 25 mg every morning (phase II), and an 8-week double-blind treatment period with diuretic plus prazosin or guanfacine (phase III). Those who had an average seated diastolic blood pressure (BP) of 95 to 114 mm Hg at the end of the phase II period were eligible to enter the phase III period and were randomly assigned to chlorthalidone plus either guanfacine, 1 mg every night, or prazosin, 1 mg three times a day. Of the 102 patients who were randomly assigned to guanfacine or prazosin, 80% completed the entire study. Guanfacine and prazosin appeared to be equally effective and reduced seated as well as standing diastolic and systolic BP. The mean seated systolic and diastolic BP were reduced 11/9 mm Hg by guanfacine and 11/10 mm Hg by prazosin. The mean reduction in seated pulse was 3 beats/minute for guanfacine and no change with prazosin. Similar changes occurred in the standing position. Very few adverse effects were reported during the study. Adverse effects with an incidence of 5% or greater for either drug group were dizziness (6% guanfacine, 8% prazosin), xerostomia (6% guanfacine, 2% prazosin), and somnolence (0% guanfacine, 6% prazosin). Three patients (6%) in the prazosin group experienced symptoms of orthostasis requiring premature discontinuation of the drug and termination from the study.

Comparison of guanfacine versus clonidine for efficacy, safety and occurrence of withdrawal syndrome in step-2 treatment of mild to moderate essential hypertension

Guanfacine, an alpha 2-adrenoceptor agonist, was compared with clonidine as step-2 therapy of mild to moderate essential hypertension in a 24-week, double-blind, randomized, parallel evaluation to determine efficacy, safety and occurrence of withdrawal syndrome. During a 5-week period, patients were weaned from current antihypertensives, if any, and stabilized on step-1 therapy with 25 mg of chlorthalidone once a day. Those with a diastolic blood pressure (BP) from 95 to 114 mm Hg while taking chlorthalidone were randomized to treatment. The 2 agents had equal efficacy; 149 of 270 patients treated with guanfacine (55%) and 164 of 276 treated with clonidine (59%) achieved goal diastolic BP of less than or equal to 90 mm Hg. Terminations because of adverse effects were relatively low. Dry mouth (30% of guanfacine and 37% of clonidine groups) and somnolence (21% of guanfacine and 35% of clonidine groups, p less than 0.05) were reported most frequently. Nonsyncopal dizziness was reported in 11% of guanfacine-treated and 8% of clonidine-treated patients. This difference was not statistically significant. To evaluate the occurrence of a withdrawal syndrome in 316 outpatients and 156 inpatients, vital signs were monitored at least twice a day for up to 7 days after the end of therapy. Segmented 24-hour urine studies were performed on inpatients. Abrupt withdrawal of clonidine produced a rapid increase in diastolic and, especially, systolic BP, whereas guanfacine withdrawal produced more gradual increases. The differences were significant over the first 3 withdrawal days. It is concluded that guanfacine is a safe, effective, second-generation alpha 2-adrenoceptor agonist.(ABSTRACT TRUNCATED AT 250 WORDS)