No

Alpha₂ Agonist

Management of hypertension

B

Hypersensitivity to guanfacine or any component

Use caution with severe coronary insufficiency, recent MI, cerebrovascular disease, or chronic renal or hepatic disease. Abrupt discontinuation can result in nervousness, anxiety and rarely, rebound hypertension (occurs 2-4 days after withdrawal). Avoid use in CNS disease, elderly, or with other CNS depressants (can cause sedation and drowsiness alone). Safety and efficacy in children <12 years of age have not been demonstrated. May cause orthostasis.

>10%:

Central nervous system: Somnolence (~10%), fatigue (12%)

Gastrointestinal: Xerostomia (47%), constipation (16%)

1% to 10%:

Central nervous system: Headache (4%), insomnia (4%), dizziness (6%)

Cardiovascular; Hypotension, orthostasis

Endocrine & metabolic: Decreased sexual ability

Gastrointestinal: Nausea, vomiting

Ocular: Conjunctivitis

<1% (Limited to important or life-threatening symptoms): Bradycardia, palpitations, substernal pain, rebound hypertension, amnesia, confusion, depression, malaise, dermatitis, pruritus, purpura, abdominal pain, diarrhea, dyspepsia, dysphagia, taste perversion, testicular disorder, urinary incontinence, leg cramps, hypokinesia, paresthesia, tinnitus, rhinitis, dyspnea, diaphoresis

TCAs decrease the hypotensive effect of guanfacine.

Hypoglycemic symptoms may be decreased. Educate patient about decreased signs and symptoms of hypoglycemia or avoid use in patients with frequent episodes of hypoglycemia.

Nitroprusside and guanfacine have additive hypotensive effects.

Noncardioselective beta-blockers (nadolol, propranolol, timolol) may exacerbate rebound hypertension when guanfacine is withdrawn. The beta-blocker should be withdrawn first. The gradual withdrawal of guanfacine or a cardioselective beta-blocker could be substituted.

Stimulates alpha₂-adrenoreceptors in the brain stem, thus activating an inhibitory neuron, resulting in reduced sympathetic outflow, producing a decrease in vasomotor tone and heart rate

Peak effect: Within 8-11 hours

Duration: 24 hours following a single dose

Serum half-life: 17 hours

Time to peak serum concentration: Within 1-4 hours

Adults: Oral: 1 mg usually at bedtime, may increase if needed at 3- to 4-week intervals; 1 mg/day is most common dose

Not routinely used in clinical practice because of significant and marked hypotension.

Drowsiness is common; may cause insomnia or dizziness, may rarely cause confusion or depression

Has been used to treat ADHD; concurrent use with psychotropics may produce additive sedation and dry mouth; TCAs may decrease the hypotensive effect of guanfacine

No information available to require special precautions

>10% of patients experience dry mouth

May impair alertness, judgment, coordination; do not abruptly discontinue; do not discontinue without notifying physician

Administer dose at bedtime

Monitor blood pressure, standing and sitting/supine; observe for orthostasis

Tablet, as hydrochloride: 1 mg, 2 mg

Cornish LA, "Guanfacine Hydrochloride: A Centrally Acting Hypertensive Agent," Clin Pharm, 1988, 7(3):187-97.

Granier P, Arsac P, and Debru JL, "Intoxication Par La Guanfacine," Nouv Presse Med, 1982, 11(21):1636-7.

Van Dyke MW, Bonace AL, and Ellenhorn MJ, "Guanfacine Overdose in a Pediatric Patient," Vet Hum Toxicol, 1990, 32(1):46-7.