Guanfacine Hydrochloride

Guanfacine tablets, USP are indicated in the management of hypertension. Guanfacine may be given alone or in combination with other antihypertensive agents, especially thiazide-type diuretics.

Guanfacine tablets, USP are contraindicated in patients with known hypersensitivity to guanfacine hydrochloride, USP.

Adverse reactions noted with guanfacine hydrochloride are similar to those of other drugs of the central α 2 -adrenoreceptor agonist class: dry mouth, sedation (somnolence), weakness (asthenia), dizziness, constipation, and impotence. While the reactions are common, most are mild and tend to disappear on continued dosing. Skin rash with exfoliation has been reported in a few cases; although clear cause and effect relationships to guanfacine could not be established, should a rash occur, guanfacine should be discontinued and the patient monitored appropriately.

In the dose-response monotherapy study described under CLINICAL PHARMACOLOGY, the frequency of the most commonly observed adverse reactions showed a dose relationship from 0.5 to 3 mg as follows: Adverse Reaction Placebo n=59 0.5 mg n=60 1 mg n=61 2 mg n=60 3 mg n=59 Dry Mouth 0% 10% 10% 42% 54% Somnolence 8% 5% 10% 13% 39% Asthenia 0% 2% 3% 7% 3% Dizziness 8% 12% 2% 8% 15% Headache 8% 8% 13% 7% 3% Impotence 0% 0% 0% 7% 3% Constipation 0% 2% 0% 5% 15% Fatigue 2% 2% 5% 8% 10% The percent of patients who dropped out because of adverse reactions are shown below for each dosage group.

Placebo 0.5 mg 1 mg 2 mg 3 mg Percent Dropouts 0% 2% 5% 13% 32% The most common reasons for dropouts among patients who received guanfacine were dry mouth, somnolence, dizziness, fatigue, weakness and constipation. In the 12-week, placebo-controlled, dose-response study of guanfacine administered with 25 mg chlorthalidone at bedtime, the frequency of the most commonly observed adverse reactions showed a clear dose relationship from 0.5 to 3 mg as follows: Adverse Reactions Placebo n=73 0.5 mg n=72 1 mg n=72 2 mg n=72 3 mg n=72 Dry Mouth 5 (7%) 4 (5%) 6 (8%) 8 (11%) 20 (28%) Somnolence 1 (1%) 3 (4%) 0 (0%) 1 (1%) 10 (14%) Asthenia 0 (0%) 2 (3%) 0 (0%) 2 (2%) 7 (10%) Dizziness 2 (2%) 1 (1%) 3 (4%) 6 (8%) 3 (4%) Headache 3 (4%) 4 (3%) 3 (4%) 1 (1%) 2 (2%) Impotence 1 (0%) 1 (0%) 0 (0%) 1 (1%) 3 (4%) Constipation 0 (0%) 1 (0%) 0 (0%) 1 (1%) 1 (1%) Fatigue 3 (3%) 0 (0%) 2 (3%) 5 (6%) 3 (4%) There were 41 premature terminations because of adverse reactions in this study.