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Pronunciation
(GWAHN a benz)
Generic Available (U.S.)
Yes
Index Terms
Canadian Brand Names
Pharmacologic Category
Pharmacologic Category Synonyms
Use: Labeled Indications
Management of hypertension
Pregnancy Risk Factor
C
Pregnancy Considerations
Teratogenic effects were observed in animal studies. There are no adequate and well-controlled studies in pregnant women.
Lactation
Excretion in breast milk unknown/use caution
Contraindications
Hypersensitivity to guanabenz or any component of the formulation
Warnings/Precautions
Concerns related to adverse effects:
• CNS effects: May cause sedation and drowsiness; avoid use in CNS disease.
• Orthostasis: May cause significant orthostasis.
Disease-related concerns:
• Cardiovascular disease: Use with caution in patients with severe coronary insufficiency or recent MI.
• Cerebrovascular disease: Use with caution in patients with cerebrovascular disease.
• Hepatic impairment: Use with caution in patients with severe hepatic impairment.
• Renal impairment: Use with caution in patients with severe renal impairment.
Concurrent drug therapy issues:
• CNS depressants: Avoid use with other CNS depressants; effects may be potentiated.
Special populations:
• Elderly: Avoid use in the elderly.
• Pediatrics: Safety and efficacy have not been established for use in children <12 years of age.
Other warnings/precautions:
• Abrupt withdrawal: Abrupt discontinuation can result in nervousness, anxiety and rarely, rebound hypertension (occurs 2-4 days after withdrawal).
Adverse Reactions
Higher rates with larger doses
>5% (at doses of 16 mg/day):
Cardiovascular: Orthostasis
Central nervous system: Drowsiness or sedation (39%), dizziness (12% to 17%), headache (5%)
Gastrointestinal: Xerostomia (28% to 38%)
Neuromuscular & skeletal: Weakness (~10%)
≤3% (may be similar to placebo):
Cardiovascular: Arrhythmias, chest pain, edema, palpitation
Central nervous system: Anxiety, ataxia, depression, sleep disturbances
Dermatologic: Pruritus, rash
Endocrine & metabolic: Disturbances of sexual function, gynecomastia, decreased sexual function
Gastrointestinal: Constipation, diarrhea, nausea, vomiting
Genitourinary: Polyuria
Neuromuscular & skeletal: Myalgia
Ocular: Blurring of vision
Respiratory: Dyspnea, nasal congestion
Miscellaneous: Taste disorders
Metabolism/Transport Effects
Substrate of CYP1A2 (major)
Drug Interactions
Abiraterone Acetate: May increase the serum concentration of CYP1A2 Substrates. Risk C: Monitor therapy
Amifostine: Antihypertensives may enhance the hypotensive effect of Amifostine. Management: When amifostine is used at chemotherapy doses, antihypertensive medications should be withheld for 24 hours prior to amifostine administration. If antihypertensive therapy can not be withheld, amifostine should not be administered. Risk D: Consider therapy modification
Antidepressants (Alpha2-Antagonist): May diminish the hypotensive effect of Alpha2-Agonists. Risk D: Consider therapy modification
Antihypertensives: May enhance the hypotensive effect of other Antihypertensives. Risk C: Monitor therapy
Beta-Blockers: May enhance the rebound hypertensive effect of Alpha2-Agonists. This effect can occur when the alpha2-agonist is abruptly withdrawn. Exceptions: Levobunolol; Metipranolol. Risk D: Consider therapy modification
CYP1A2 Inducers (Strong): May increase the metabolism of CYP1A2 Substrates. Risk C: Monitor therapy
CYP1A2 Inhibitors (Moderate): May decrease the metabolism of CYP1A2 Substrates. Risk C: Monitor therapy
CYP1A2 Inhibitors (Strong): May decrease the metabolism of CYP1A2 Substrates. Risk D: Consider therapy modification
Deferasirox: May increase the serum concentration of CYP1A2 Substrates. Risk C: Monitor therapy
Diazoxide: May enhance the hypotensive effect of Antihypertensives. Risk C: Monitor therapy
Herbs (Hypertensive Properties): May diminish the antihypertensive effect of Antihypertensives. Risk C: Monitor therapy
Herbs (Hypotensive Properties): May enhance the hypotensive effect of Antihypertensives. Risk C: Monitor therapy
Hypotensive Agents: May enhance the adverse/toxic effect of other Hypotensive Agents. Risk C: Monitor therapy
Iobenguane I 123: Alpha2-Agonists may diminish the therapeutic effect of Iobenguane I 123. Risk X: Avoid combination
MAO Inhibitors: May enhance the orthostatic hypotensive effect of Orthostatic Hypotension Producing Agents. Risk C: Monitor therapy
Methylphenidate: May diminish the antihypertensive effect of Antihypertensives. Risk C: Monitor therapy
Pentoxifylline: May enhance the hypotensive effect of Antihypertensives. Risk C: Monitor therapy
Phosphodiesterase 5 Inhibitors: May enhance the antihypertensive effect of Antihypertensives. Risk C: Monitor therapy
Prostacyclin Analogues: May enhance the hypotensive effect of Antihypertensives. Risk C: Monitor therapy
RiTUXimab: Antihypertensives may enhance the hypotensive effect of RiTUXimab. Risk D: Consider therapy modification
Serotonin/Norepinephrine Reuptake Inhibitors: May diminish the antihypertensive effect of Alpha2-Agonists. Risk C: Monitor therapy
Tricyclic Antidepressants: May diminish the antihypertensive effect of Alpha2-Agonists. Risk D: Consider therapy modification
Yohimbine: May diminish the antihypertensive effect of Antihypertensives. Risk C: Monitor therapy
Storage
Protect from light.
Mechanism of Action
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
Pharmacodynamics/Kinetics
Onset of action: Antihypertensive: ~1 hour
Absorption: ~75%
Half-life elimination, serum: 7-10 hours
Dosage
Adults: Oral: Initial: 4 mg twice daily; increase in increments of 4-8 mg/day every 1-2 weeks to a maximum of 32 mg twice daily.
Dosing adjustment in hepatic impairment: Probably necessary
Monitoring Parameters
Monitor blood pressure, standing and sitting/supine
Geriatric Considerations
Because of its CNS adverse effects, guanabenz is not considered a drug of choice for the treatment of hypertension in the elderly.
Additional Information
Considered an alternate to clonidine; it causes less sodium retention than clonidine or methyldopa.
Anesthesia and Critical Care Concerns/Other Considerations
Guanabenz is not routinely used in clinical practice because of significant and marked orthostatic hypotension.
Cardiovascular Considerations
Not routinely used in clinical practice because of significant and marked orthostatic hypotension.
Dental Health: Effects on Dental Treatment
Key adverse event(s) related to dental treatment: Taste disorder, nasal congestion, dyspnea, significant xerostomia (normal salivary flow resumes upon discontinuation).
Dental Health: Vasoconstrictor/Local Anesthetic Precautions
No information available to require special precautions
Mental Health: Effects on Mental Status
Drowsiness and dizziness are common; may cause anxiety or depression
Mental Health: Effects on Psychiatric Treatment
Has been used to treat ADHD; concurrent use with psychotropics may produce additive sedation and dry mouth; TCAs may decrease the hypotensive effect of guanabenz
Dosage Forms
Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product
Tablet, oral: 4 mg, 8 mg [DSC]
Pricing: U.S. (www.drugstore.com)
Tablets (Guanabenz Acetate)
8 mg (60): $102.92
References
Chobanian AV, Bakris GL, Black HR, et al, “The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: The JNC 7 Report,” JAMA, 2003, 289(19):2560-71.
International Brand Names
Lexi-Comp.com
Last full review/revision May 2011
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