Gaunfacine
FDA Drug Information • Also known as: Guanfacine
- Brand Names
- Guanfacine
- Route
- ORAL
- Dosage Form
- TABLET
- Product Type
- HUMAN PRESCRIPTION DRUG
Description
DESCRIPTION Guanfacine Tablets, USP are a centrally acting antihypertensive with α2-adrenoceptor agonist properties in tablet form for oral administration. The chemical name of guanfacine hydrochloride is N-amidino- 2-(2,6-dichlorophenyl) acetamide hydrochloride and its molecular weight is 282.56. Its structural formula is: Guanfacine hydrochloride is a white to off-white powder; sparingly soluble in water and alcohol and slightly soluble in acetone. Each tablet, for oral administration, contains guanfacine hydrochloride, USP equivalent to 1 mg or 2 mg of guanfacine. In addition, each tablet contains the following inactive ingredients: microcrystalline cellulose, anhydrous lactose, pregelatinized starch and magnesium stearate. Guanfacine Tablets, USP meets USP Dissolution Test 2. chemical
What Is Gaunfacine Used For?
INDICATIONS AND USAGE Guanfacine Tablets, USP are indicated in the management of hypertension. Guanfacine hydrochloride may be given alone or in combination with other antihypertensive agents, especially thiazide-type diuretics.
Dosage and Administration
DOSAGE AND ADMINISTRATION The recommended initial dose of guanfacine hydrochloride when given alone or in combination with another antihypertensive drug is 1 mg daily given at bedtime to minimize somnolence. If after 3 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 hydrochloride is 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 - 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 - 4 days) without ill effects.
Side Effects (Adverse Reactions)
ADVERSE REACTIONS Adverse reactions noted with guanfacine hydrochloride are similar to those of other drugs of the central 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 hydrochloride could not be established, should a rash occur, guanfacine hydrochloride 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=60 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. Placebo 0.5 mg 1 mg 2 mg 3 mg Percent dropouts 0% 2.0% 5.0% 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: Adeverse 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 (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. The percent of pateints who dropped out and the dose at which the dropout occurred were as follows: Dose Placebo 0.5 mg 1 mg 2 mg 3 mg Percent dropouts 6.9% 4.2% 3.2% 6.9% 8.3% 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. In a second 12-week placebo-controlled combination therapy study in which the dose could be adjusted upward to 3 mg per day in 1-mg increments at 3-week intervals, i.e., 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,...
Drug Interactions
Drug Interactions The potential for increased sedation when guanfacine hydrochloride is given with other CNS-depressant drugs should be appreciated. The administration of guanfacine concomitantly with a known microsomal enzyme inducer (phenobarbital or phenytoin) to two patients with renal impairment reportedly resulted in significant reductions in elimination half-life and plasma concentration. In such cases, therefore, more frequent dosing may be required to achieve or maintain the desired hypotensive response. Further, if guanfacine is to be discontinued in such patients, careful tapering of the dosage may be necessary in order to avoid rebound phenomena (see Rebound above). Anticoagulants Ten patients who were stabilized on oral anticoagulants were given guanfacine, 1 - 2 mg/day, for 4 weeks. No changes were observed in the degree of anticoagulation. In several well-controlled studies, guanfacine was administered together with diuretics with no drug interactions reported. In the long-term safety studies, guanfacine hydrochloride was given concomitantly with many drugs without evidence of any interactions. The principal drugs given (number of patients in parentheses) were: cardiac glycosides (115), sedatives and hypnotics (103), coronary vasodilators (52), oral hypoglycemics (45), cough and cold preparations (45), NSAIDs (38), antihyperlipidemics (29), antigout drugs (24), oral contraceptives (18), bronchodilators (13), insulin (10), and beta blockers (10). Drug/Laboratory Test Interactions No laboratory test abnormalities related to the use of guanfacine hydrochloride have been identified.
Contraindications
CONTRAINDICATIONS Guanfacine Tablets, USP is contraindicated in patients with known hypersensitivity to guanfacine hydrochloride.
Overdosage
OVERDOSAGE Signs and Symptoms Drowsiness, lethargy, bradycardia and hypotension have been observed following overdose with guanfacine. A 25-year-old female intentionally ingested 60 mg. She presented with severe drowsiness and bradycardia of 45 beats/minute. Gastric lavage was performed and an infusion of isoproterenol (0.8 mg in 12 hours) was administered. She recovered quickly and without sequelae. A 28-year-old female who ingested 30 - 40 mg developed only lethargy, was treated with activated charcoal and a cathartic, was monitored for 24 hours, and was discharged in good health. A 2-year-old male weighing 12 kg who ingested up to 4 mg of guanfacine developed lethargy. Gastric lavage (followed by activated charcoal and sorbitol slurry via NG tube) removed some tablet fragments within 2 hours after ingestion, and vital signs were normal. During 24-hour observation in ICU, systolic pressure was 58 and heart rate 70 at 16 hours post- ingestion. No intervention was required, and child was discharged fully recovered the next day. Treatment of Overdosage Gastric lavage and supportive therapy as appropriate. Guanfacine is not dialyzable in clinically significant amounts (2.4%).
How Supplied
Guanfacine Tablets, USP are available in the following dosing strengths (expressed in equivalent amounts of guanfacine): 2 mg—White round tablets, debossed “i3” on one side and “19” on the other side in NDC: 70518-4564-00 PACKAGING: 30 in 1 BLISTER PACK Store at controlled temperature, between 20°C and 25°C (68°F and 77°F). Dispense in a tight, light-resistant container. Repackaged and Distributed By: Remedy Repack, Inc. 625 Kolter Dr. Suite #4 Indiana, PA 1-724-465-8762
About This Information
This drug information is sourced from FDA-approved labeling via the openFDA database. It is intended for educational and reference purposes only. This is not medical advice. Always consult your healthcare provider before making decisions about medication. Drug information may be updated by the FDA; check with your pharmacist for the most current information.
What are side effects?
Side effects are unwanted reactions that can occur when taking a medication. They range from mild (headache, nausea) to severe (allergic reactions, organ damage). Not everyone experiences side effects, and severity varies. Report any concerning side effects to your doctor.
What are drug interactions?
Drug interactions occur when a medication is affected by another drug, food, or supplement. Interactions can make medications less effective or cause dangerous side effects. Always tell your doctor about all medications and supplements you take.