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Guanfacine is a brand name for Guanfacine. The medicine, its uses, side effects and dosage are the same regardless of brand.
Used for: INDICATIONS AND USAGE Guanfacine tablets, USP are indicated in the management of hypertension. Guanfacine tablets, USP may be given alone or in combination with other antihypertensive agents, especially thiazide-type diuretics.
Verbatim from this product's FDA label. Tap a section to expand.
DOSAGE AND ADMINISTRATION
The recommended initial dose of guanfacine tablets when given alone or in combination with another antihypertensive drug is 1 mg daily given at bedtime to minimize somnolence. If after 3 weeks to 4 weeks of therapy 1 mg does not give a satisfactory result, a dose of 2 mg may be given, although most of the effect of guanfacine tablets are seen at 1 mg (see CLINICAL PHARMACOLOGY ).
Higher daily doses have been used, but adverse reactions increase significantly with doses above 3 mg/day. The frequency of rebound hypertension is low, but it can occur. When rebound occurs, it does so after 2 days to 4 days, which is delayed compared with clonidine hydrochloride.
This is consistent with the longer half-life of guanfacine. In most cases, after abrupt withdrawal of guanfacine, blood pressure returns to pretreatment levels slowly (within 2 days to 4 days) without ill effects.
ADVERSE REACTIONS
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 tablets could not be established, should a rash occur, guanfacine tablets should be discontinued and the patient monitored appropriately.
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 % 13 % 7 % 5 % 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.
0 % 13 % 32 % The most common reasons for dropouts among patients who received guanfacine were dry mouth, somnolence, dizziness, fatigue, weakness, and constipation. 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 (1 %) 1 (0 %) 0 (0 %) 1 (1 %) 3 (4 %) Constipation 0 (0 %) 0 (0 %) 0 (0 %) 1 (1 %) 1 (1 %) Fatigue 3 (3 %) 2 (3 %) 2 (3 %) 5 (6 %) 3 (4 %) There were 41 premature terminations because of adverse reactions in this study.
3 % Reasons for dropouts among patients who received guanfacine were: somnolence, headache, weakness, dry mouth, dizziness, impotence, insomnia, constipation, syncope, urinary incontinence, conjunctivitis, paresthesia, and dermatitis.
CONTRAINDICATIONS
Guanfacine tablets are contraindicated in patients with known hypersensitivity to guanfacine hydrochloride.
Not medical advice. Always read the patient information leaflet and follow your prescriber or pharmacist.
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, a setting more similar to ordinary clinical use, the most commonly recorded reactions were: dry mouth, 47 %; constipation, 16 %; fatigue, 12 %; somnolence, 10 %; asthenia, 6 %; dizziness, 6 %; headache, 4 %; and insomnia, 4 %. Reasons for dropouts among patients who received guanfacine were: somnolence, dry mouth, dizziness, impotence, constipation, confusion, depression, and palpitations.
In the clonidine/guanfacine comparison described in CLINICAL PHARMACOLOGY , the most common adverse reactions noted were as follows: Adverse Reactions Guanfacine (n = 279) Clonidine (n = 278) Dry Mouth 30 % 37 % Somnolence 21 % 35 % Dizziness 11 % 8 % Constipation 10 % 5 % Fatigue 9 % 8 % Headache 4 % 4 % Insomnia 4 % 3 % Adverse reactions occurring in 3 % or less of patients in the three controlled trials of guanfacine hydrochloride with a diuretic were: Cardiovascular- bradycardia, palpitations, substernal pain Gastrointestinal- abdominal pain, diarrhea, dyspepsia, dysphagia, nausea CNS- amnesia, confusion, depression, insomnia, libido decrease ENT disorders- rhinitis, taste perversion, tinnitus Eye disorders- conjunctivitis, iritis, vision disturbance Musculoskeletal- leg cramps, hypokinesia Respiratory- dyspnea Dermatologic- dermatitis, pruritus, purpura, sweating Urogenital- testicular disorder, urinary incontinence Other- malaise, paresthesia, paresis Adverse reaction reports tend to decrease over time.
In an open-label trial of one year's duration, 580 hypertensive subjects were given guanfacine, titrated to achieve goal blood pressure, alone (51 %), with diuretic (38 %), with beta blocker (3 %), with diuretic plus beta blocker (6 %), or with diuretic plus vasodilator (2 %).
7 mg. 9 %) dropouts due to adverse effects in this 1-year trial. The causes were: dry mouth (n = 20), weakness (n = 12), constipation (n = 7), somnolence (n = 3), nausea (n = 3), orthostatic hypotension (n = 2), insomnia (n = 1), rash (n = 1), nightmares (n = 1), headache (n = 1), and depression (n = 1).
Postmarketing Experience An open-label postmarketing study involving 21,718 patients was conducted to assess the safety of guanfacine hydrochloride 1 mg/day given at bedtime for 28 days. Guanfacine tablets were administered with or without other antihypertensive agents.
Adverse events reported in the postmarketing study at an incidence greater than 1 % included dry mouth, dizziness, somnolence, fatigue, headache and nausea. The most commonly reported adverse events in this study were the same as those observed in controlled clinical trials.
Less frequent, possibly guanfacine tablets-related events observed in the postmarketing study and/or reported spontaneously include: BODY AS A WHOLE asthenia, chest pain, edema, malaise, tremor CARDIOVASCULAR bradycardia, palpitations, syncope, tachycardia CENTRAL NERVOUS SYSTEM paresthesias, vertigo EYE DISORDERS blurred vision GASTROINTESTINAL SYSTEM abdominal pain, constipation, diarrhea, dyspepsia LIVER AND BILLIARY SYSTEM abnormal liver function tests MUSCULO-SKELETAL SYSTEM arthralgia, leg cramps, leg pain, myalgia PSYCHIATRIC agitation, anxiety, confusion, depression, insomnia, nervousness REPRODUCTIVE SYSTEM, Male- impotence RESPIRATORY SYSTEM dyspnea SKIN AND APPENDAGES alopecia, dermatitis, exfoliative dermatitis, pruritus, rash SPECIAL SENSES alterations in taste URINARY SYSTEM nocturia, urinary frequency Rare, serious disorders with no definitive cause and effect relationship to guanfacine tablets have been reported spontaneously and/or in the postmarketing study.
These events include acute renal failure, cardiac fibrillation, cerebrovascular accident, congestive heart failure, heart block, and myocardial infarction.