Guanfacine hydrochloride
Guanfacine hydrochloride (Tenex)
Guanfacine hydrochloride
( GWON-fah-seen)
Pregnancy Category: B Tenex (Rx)

Classification: Antihypertensive, centrally acting

See Also: See also Antihypertensive Agents .

Action/Kinetics: Thought to act by central stimulation of alpha-2 receptors. Causes a decrease in peripheral sympathetic output and HR resulting in a decrease in BP. May also manifest a direct peripheral alpha-2 receptor stimulant action. Onset: 2 hr. Peak plasma levels: 1-4 hr. Peak effect: 6-12 hr. t 1/2: 12-23 hr. Duration: 24 hr. Approximately 50% excreted through the kidneys unchanged.

Uses: Hypertension alone or with a thiazide diuretic. Investigational: Withdrawal from heroin use, to reduce the frequency of migraine headaches.

Contraindications: Hypersensitivity to guanfacine. Acute hypertension associated with toxemia. Children less than 12 years of age.

Special Concerns: Use with caution during lactation and in clients with recent MI, cerebrovascular disease, chronic renal or hepatic failure, or severe coronary insufficiency. Geriatric clients may be more sensitive to the hypotensive and sedative effects. Safety and efficacy in children less than 12 years of age have not been determined.

Side Effects: GI: Dry mouth, constipation, nausea, abdominal pain, diarrhea, dyspepsia, dysphagia, taste perversion or alterations in taste. CNS: Sedation, weakness, dizziness, headache, fatigue, insomnia, amnesia, confusion, depression, vertigo, agitation, anxiety, malaise, nervousness, tremor. CV: Bradycardia, substernal pain, palpitations, syncope, chest pain, tachycarida, cardiac fibrillation, CHF, heart block, MI (rare), cardiovascular accident (rare). Ophthalmic: Visual disturbances, conjunctivitis, iritis, blurred vision. Dermatologic: Pruritus, dermatitis, purpura, sweating, skin rash with exfoliation, alopecia, rash. GU: Decreased libido, impotence, urinary incontinence or frequency, testicular disorder, nocturia, acute renal failure. Musculoskeletal: Leg cramps, hypokinesia, arthralgia, leg pain, myalgia. Other: Rhinitis, tinnitus, dyspnea, paresthesias, paresis, asthenia, edema, abnormal LFTs.

Overdose Management: Symptoms: Drowsiness, bradycardia, lethargy, hypotension. Treatment: Gastric lavage. Supportive therapy, as needed. The drug is not dialyzable.

Drug Interactions: Additive sedative effects when used concomitantly with CNS depressants.

How Supplied: Tablet: 1 mg, 2 mg

Dosage
?Tablets Hypertension.
Initial: 1 mg/day alone or with other antihypertensives; if satisfactory results are not obtained in 3-4 weeks, dosage may be increased by 1 mg at 1-2-week intervals up to a maximum of 3 mg/day in one to two divided doses.
Heroin withdrawal.
0.03-1.5 mg/day.
Reduce frequency of migraine headaches.
1 mg/day for 12 weeks.