| GUANABENZ ACETATE
Classifications: alpha-adrenergic agonist; central-acting antihypertensive; Therapeutic: antihypertensive
Pregnancy Category: C
4 mg, 8 mg tablets
Centrally acting alpha2-adrenergic agonist. Pharmacologic actions closely resemble those of clonidine. Lowers BP, primarily by stimulating central
alpha-adrenergic receptors that lead to inhibition of sympathetic outflow from brain. Has no effect on exercise tolerance
or on potassium levels.
Reduces both supine and standing BP, usually without producing postural hypotension, and slightly lowers pulse rate. Given
the fact that central adrenergic hyperactivity causes symptoms of narcotic withdrawal, guanabenz appears to help control
abstinence symptoms by reducing norepinephrine output.
Used alone in treatment of hypertension or in combination with a thiazide diuretic.
Opiate detoxification, analgesic for chronic pain.
Pregnancy (category C), lactation. Safe use in children is not established.
Severe coronary insufficiency, recent MI, cerebrovascular disease, severe hepatic or renal failure; older adults; concurrent
use of MAOI therapy.
Route & Dosage
Adult: PO 4 mg b.i.d., may increase by 48 mg/d q12wk up to 32 mg b.i.d.
Geriatric: PO 4 mg once daily, may increase every 12 wk
Adult: PO 4 mg b.i.d. to q.i.d.
- Give one dose at bedtime to ensure overnight control and reduce possibility of daytime drowsiness or sedation.
- Store at 15°30° C (59°86° F) in tightly closed containers unless otherwise directed.
Adverse Effects (≥1%)CNS: Drowsiness
dizziness, weakness, headache, anxiety, ataxia, depression
, sleep disturbances, somnolence. CV:
Chest pain, edema, arrhythmias, palpitation, hypotension, bradycardia, nervousness. GI: Dry mouth,
nausea, epigastric pain, diarrhea
, vomiting, constipation
, abdominal discomfort, taste disorders. Urogenital:
Increased urination, urinary frequency, sexual dysfunction. Special Senses:
Blurred vision, miosis, nasal congestion. Body as a Whole: Dyspnea
, muscle aches, aches in extremities, lethargy, irritability, unusual fatigue
or weakness. Skin:
and other cns depressants
depression; tricyclic antidepressants
may reduce antihypertensive effects of guanabenz.
75% absorbed from GI tract. Onset:
60 min. Peak:
25 h. Duration:
612 h. Distribution:
Widely distributed; crosses bloodbrain barrier; not known if crosses placenta or distributed into breast milk. Metabolism:
Extensively metabolized. Elimination:
80% in urine; 20% in feces. Half-Life:
Assessment & Drug Effects
- Monitor BP and HR. Report palpitations or hypotension to physician.
- Evaluate mental status and alertness.
- Lab tests: Baseline and periodic blood chemistry (serum potassium, CBC, creatinine, uric acid, cholesterol, glucose), urinalysis
for protein and sugar, and ECG.
- Give early attention and specific treatment to dry mouth. It can interfere with patient's food and fluid intake; deprivation
of normal salivary flow is a potential dental hazard since it favors demineralization of teeth; and it can be a factor in
Patient & Family Education
- Make all position changes slowly and in stages in the event that you experience orthostatic hypotension. This is important
in older adults, who tend to be more sensitive to normal adult doses of antihypertensive drugs because of deficient baroreceptor
- Do not omit a dose or stop drug therapy without consulting physician. Do not discontinue therapy abruptly; can cause sympathetic
overactivity (anxiety, nervousness, palpitation, chest pain, fast or irregular heartbeat, trembling, flushing, headache,
increased sweating and salivation, elevation of BP, usually above basal level).
- Do not drive or engage in potentially hazardous activities until response to drug is known. Also, guanabenz may reduce tolerance
to alcohol and other CNS depressants.