Penbutolol Sulfate

A to Z Drug Facts

 Action Nonselectively blocks beta-adrenergic receptors, primarily affecting the cardiovascular system (eg, decreased heart rate, decreased cardiac contractility, decreased BP) and lungs (promotes bronchospasm).

 Indications Management of mild-to-moderate hypertension.

 Contraindications Greater than first-degree heart block; CHF unless secondary to tachyarrhythmia or untreated hypertension treatable with beta-blockers; overt cardiac failure; sinus bradycardia; cardiogenic shock; hypersensitivity to beta-blockers; untreated bronchial asthma or bronchospasm, including severe COPD.

 Route/Dosage

ADULTS: PO 20 mg qd.

 Interactions

Clonidine: May attenuate or reverse antihypertensive effect; potentially life-threatening increases in BP, especially on withdrawal. Epinephrine: Initial hypertensive episodes followed by bradycardia may occur. Ergot alkaloids: Peripheral ischemia, manifested by cold extremities and possible gangrene. Insulin: Prolonged hypoglycemia with masking of symptoms. Lidocaine: Increased lidocaine levels, leading to toxicity. Nonsteroidal anti-inflammatory agents: Some agents may impair antihypertensive effects. Theophylline: Elimination of theophylline may be reduced; effects of both drugs may be reduced by pharmacologic antagonism. Verapamil: Effects of both drugs may be increased.

 Lab Test Interferences None well documented.

 Adverse Reactions

CV: Bradycardia; hypotension; congestive heart failure; edema; worsening angina, atrioventricular (AV) block. CNS: Dizziness; tiredness; fatigue; headache; insomnia; depression; short-term memory loss; emotional lability. DERM: Sweating. EENT: Dry eyes; visual disturbances. GI: Diarrhea; nausea; dyspepsia. GU: Impotence. HEMA: Agranulocytosis; nonthrombocytopenic and thrombocytopenic purpura. META: May increase or decrease blood sugar. RESP: Cough; dyspnea; bronchospasm.

 Precautions

Pregnancy: Category C. Lactation: Undetermined. Children: Safety and efficacy not established. CHF: Administer cautiously in CHF patients controlled by digitalis and diuretics. Diabetics: May mask signs and symptoms of hypoglycemia (eg, tachycardia, BP changes). May potentiate insulin-induced hypoglycemia. Nonallergic bronchospasm: Give drug with caution to patients with bronchospastic disease. Thyrotoxicosis: May mask clinical signs of developing or continuing hyperthyroidism (eg, tachycardia). Abrupt withdrawal may exacerbate symptoms of hyperthyroidism, including thyroid storm. Abrupt withdrawal: A beta-blocker withdrawal syndrome (eg, hypertension, tachycardia, anxiety, angina, MI) may occur 1 to 2 weeks after sudden discontinuation of systemic beta-blockers. If possible, gradually withdraw therapy over 1 to 2 weeks. Anaphylaxis: May be unresponsive to usual doses of epinephrine; aggressive therapy may be required. Peripheral vascular disease: May precipitate or aggravate symptoms of arterial insufficiency.

 Administration/Storage

• May be taken with or without food.
• Store tablets at room temperature in a tightly closed, light-resistant container.

 Assessment/Interventions

• Obtain patient history.
• Evaluate current ECG for signs of bradycardia or heart block.
• Monitor for bradycardia, hypotension, respiratory difficulty, and heart block that may indicate need for reduced dosage.
• Avoid use in patients with asthma, chronic bronchitis, and other chronic respiratory diseases.
• Monitor I&O and daily weight during therapy for signs of fluid retention. If sudden, severe dyspnea or edema of hands and feet develop, withhold medication and notify physician.
• Notify physician at first sign or symptom of CHF or unexplained respiratory symptoms in any patient.

 Patient/Family Education

• Warn patient to never stop taking this medication suddenly. Rebound effects can produce angina, and even MI. Explain that medication will be tapered slowly before discontinuation.
• Instruct patient to take medication at the same time every day.
• Advise patient not to take any otc medications such as nasal decongestants, diet aids, cold preparations, or antihistamines without consulting the health care provider first.
• Teach patient and family how to take pulse. Instruct them to check it before taking the medication. If the pulse is irregular or has a rate less than 60 BPM, notify health care provider before taking the medication.
• Instruct patient and family on how to take BP. If BP is markedly lower than normal, notify health care provider.
• Warn patient that sudden position changes may cause dizziness due to postural hypotension.
• Instruct patient to notify health care provider if any of the following occur: Confusion, depression, memory loss, rash, shortness of breath, slowed pulse rate, or unusual bruising, or bleeding.

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