Guanadrel

A to Z Drug Facts

 Action 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.

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

 Contraindications Pheochromocytoma; concurrent use or use within 1 wk of monoamine oxidase (MAO) inhibitors; frank CHF.

 Route/Dosage

ADULTS: PO 10 mg/day (5 mg bid) initially. Maintenance dose: PO 20 to 75 mg/day, usually in 2 divided doses; tid or qid dosing may be needed. In patients with renal impairment, dosage adjustment may be necessary.

 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. MAO inhibitors, phenothiazines, tricyclic antidepressants: Inhibit antihypertensive effect.

 Lab Test Interferences None well documented.

 Adverse Reactions

CV: 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/vomiting; abdominal distress or pain. GU: Nocturia; urination urgency or frequency; ejaculation disturbances; impotence; hematuria; decreased urine output. RESP: Shortness of breath; coughing. OTHER: 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 hr before elective surgery to prevent vascular collapse during anesthesia; for emergency surgery, preanesthetic and anesthetic agents are administered in reduced dosage.

 Administration/Storage

• Administer medication with food or milk.
• Store at room temperature.

 Assessment/Interventions

• Obtain patient history, including drug history and any known allergies. Note any CHF, renal disease, asthma and pheochromocytoma.
• Take patient's BP (lying, sitting, standing) and pulse before administering drug. Monitor periodically throughout therapy.
• Assess for symptoms of CHF: Edema, dyspnea, wet rales.
• Notify health care provider if any of these signs occur: Hypotension, chest pain, bradycardia, edema, dyspnea, coughing, confusion, syncope, nausea, oliguria, hematuria, excessive weight loss or gain.

 Patient/Family Education

• 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.
• Instruct patient not to take otc medications without consulting health care provider.

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Copyright © 2003 Facts and Comparisons
David S. Tatro
A to Z Drug Facts