Dosing & Uses
Dosage Forms & Strengths
Initial dose: 4 mg PO q12hr intially; may increase dose by 4-8 mg/day at 1-2 week intervals
Maintenance dose range is typically 4-16 mg PO q12hr
Not to exceed 32 mg PO q12hr
Safety and effectiveness not established
Adverse CNS effects; may cause bradycardia and orthostatic hypotension; not recommended as routine treatment for hypertension (Beers criteria)
Not drug of choice in elderly because of CNS effects
4 mg PO qDay, gradually increase q1-2weeks
Serious - Use Alternative
Significant - Monitor Closely
Dry mouth (12-37%)
Chest pain (3%)
Abdominal pain (3%)
Blurred vision (3%)
Nasal congestion (3%)
Frequency Not Defined
Rebound HTN with abrupt discontinuance
Hypersensitivity to guanabenz
Avoid abrupt withdrawal (rebound hypertension)
CVD, recent MI, sedation, severe coronary insufficiency liver disease, renal impairment
Avoid during breast-feeding
Pregnancy & Lactation
Pregnancy Category: C
Lactation: excretion in milk unknown; use with caution
A:Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B:May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C:Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D:Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X:Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA:Information not available.
Mechanism of Action
Central sympatholytic via alpha-2-agonist activity resulting in decreased PVR and HR
Onset: initial effect: 60 min; max effect: 2-4 hr
Peak plasma time: 2-5 hr
Duration: 10-12 hr
Protein binding: 90%
Vd: 7.4-13.4 L/kg
Metabolites: para-hydroxy guanabenz; 2,6-dichlorobenzaldehyde azine (inactive)
Half-Life: 6 hr
Dialyzable: HD: No, PD: No
Excretion: Feces 16%, urine <1%