guanabenz (Discontinued)

Brand and Other Names:Wytensin
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Dosing & Uses

AdultPediatricGeriatric

Dosage Forms & Strengths

tablet

  • 4mg
  • 8mg
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Hypertension

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

Hypertension

4 mg PO qDay, gradually increase q1-2weeks

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Interactions

Interaction Checker

and guanabenz

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    No Interactions Found
    Interactions Found

    Contraindicated

      Serious - Use Alternative

        Significant - Monitor Closely

          Minor

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            Adverse Effects

            >10%

            Sedation/somnolence (20-50%)

            Dry mouth (12-37%)

            Dizziness (12-17%)

            1-10%

            Weakness (4%)

            Chest pain (3%)

            Edema (3%)

            Palpitations (3%)

            Anxiety (3%)

            Ataxia (3%)

            Depression (3%)

            Pruritus (3%)

            Rash (3%)

            Gynecomastia (3%)

            Abdominal pain (3%)

            Constipation (3%)

            Diarrhea (3%)

            Nausea (3%)

            Vomiting (3%)

            Myalgia (3%)

            Blurred vision (3%)

            Dyspnea (3%)

            Nasal congestion (3%)

            Frequency Not Defined

            Rebound HTN with abrupt discontinuance

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            Warnings

            Contraindications

            Hypersensitivity to guanabenz

            Cautions

            Avoid abrupt withdrawal (rebound hypertension)

            CVD, recent MI, sedation, severe coronary insufficiency liver disease, renal impairment

            Avoid during breast-feeding

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            Pregnancy & Lactation

            Pregnancy Category: C

            Lactation: excretion in milk unknown; use with caution

            Pregnancy Categories

            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.

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            Pharmacology

            Mechanism of Action

            Central sympatholytic via alpha-2-agonist activity resulting in decreased PVR and HR

            Absorption

            Bioavailability: 75%

            Onset: initial effect: 60 min; max effect: 2-4 hr

            Peak plasma time: 2-5 hr

            Duration: 10-12 hr

            Distribution

            Protein binding: 90%

            Vd: 7.4-13.4 L/kg

            Metabolism

            Liver

            Metabolites: para-hydroxy guanabenz; 2,6-dichlorobenzaldehyde azine (inactive)

            Elimination

            Half-Life: 6 hr

            Dialyzable: HD: No, PD: No

            Excretion: Feces 16%, urine <1%

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