Guanadrel

Pronunciation: GWAHN-uh-drell
Class: Antiadrenergic, peripherally acting

Trade Names:
Hylorel
- Tablets 10 mg
- Tablets 25 mg

Pharmacology

Inhibits vasoconstriction by restraining norepinephrine release from nerve storage sites; depletion of norepinephrine causes relaxation of vascular smooth muscle, decreasing total peripheral resistance, and venous return.

Pharmacokinetics

Absorption

T max is 1.5 to 2 h.

Elimination

T 1/ 2 is about 10 h. About 85% is excreted in the urine, about 40% as unchanged drug.

Special Populations

Renal Function Impairment

Total Cl decreases and t 1/ 2 is prolonged. Dosage adjustment may be necessary.

Indications and Usage

Treatment of hypertension in patients not responding adequately to thiazide-type diuretics.

Contraindications

Pheochromocytoma; concurrent use or use within 1 wk of MAOIs; frank CHF.

Dosage and Administration

Adults

PO 10 mg/day (5 mg twice daily) initially. Maintenance dose: PO 20 to 75 mg/day, usually in 2 divided doses; 3 or 4 times daily dosing may be needed. In patients with renal function impairment, dosage adjustment may be necessary.

Storage/Stability

Store at room temperature.

Drug Interactions

Alpha-blockers, beta-blockers, reserpine

Effects of guanadrel may be potentiated, resulting in excessive orthostatic hypotension and bradycardia.

Indirect-acting sympathomimetics (eg, ephedrine)

Reverse antihypertensive effect.

MAOIs, phenothiazines, tricyclic antidepressants

Inhibit antihypertensive effect.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

Palpitations; chest pain; peripheral edema; orthostatic hypotension; syncope.

CNS

Fatigue; headache; faintness; drowsiness; paresthesias; confusion; depression; sleep disorders.

EENT

Dilated pupils; visual disturbances; glossitis.

GI

Increased bowel movements; gas pain/indigestion; constipation; anorexia; nausea or vomiting; abdominal distress or pain.

Genitourinary

Nocturia; urination urgency or frequency; ejaculation disturbances; impotence; hematuria; decreased urine output.

Respiratory

Shortness of breath; coughing.

Miscellaneous

Excessive weight loss or gain; aching limbs; leg cramps; back or neckache; joint pain or inflammation; gangrene.

Precautions

Pregnancy

Category B .

Lactation

Undetermined.

Children

Safety and efficacy not established.

Asthma

Drug may aggravate asthma because of depletion of catecholamines; drugs used to treat asthma may reduce hypotensive effect of guanadrel.

Surgery

Discontinue 48 to 72 h before elective surgery to prevent vascular collapse during anesthesia; for emergency surgery, preanesthetic and anesthetic agents are administered in reduced dosage.

Overdosage

Symptoms

Marked dizziness, blurred vision, syncope, orthostatic hypotension.

Patient Information

  • Teach proper technique for taking BP. Advise patient to check BP weekly.
  • Instruct patient not to discontinue drug abruptly.
  • Advise patient about benefits of weight reduction, exercise, reduction of alcohol and sodium intake, cessation of smoking.
  • Tell patient to lie down if dizziness or blurred vision occurs.
  • Explain that impotence or ejaculation disturbance may occur but is reversible. Tell patient to report to health care provider.
  • Instruct patient to report these symptoms to health care provider: headache, dizziness, myalgia, depression, chest pain, nausea, visual disturbances.
  • Caution patient to avoid sudden position changes to prevent orthostatic hypotension.
  • Caution patient to avoid intake of alcoholic beverages or other CNS depressants.
  • Advise patient that drug may cause drowsiness and to use caution while driving or performing other tasks requiring mental alertness.

Copyright © 2009 Wolters Kluwer Health.

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