PENBUTOLOL

PENBUTOLOL (pen-bu'tol-ol) Levatol Classifications: beta-adrenergic antagonist; antihypertensive; Therapeutic: antihypertensive Prototype: Propranolol Pregnancy Category: C

Availability

20 mg tablets

Action

Synthetic beta₁- and beta₂-adrenergic blocking agent which competes with epinephrine and norepinephrine for available beta receptor sites. Lowers both supine and standing BP in hypertensive patients. Hypotensive effect is associated with decreased cardiac output, suppressed renin activity as well as beta blockage.

Therapeutic Effect

Effective in lowering mild to moderate blood pressure.

Uses

Mild to moderate hypertension alone or with other antihypertensive agents.

Contraindications

Clients with cardiogenic shock, acute CHF, sinus bradycardia, second and third degree AV block; bronchial asthma, COPD; hypersensitivity to the drug; pregnancy (category C).

Cautious Use

Cardiac failure; chronic bronchitis; diabetes; mental depression; myasthenia gravis; renal disease; lactation. Safety and effectiveness in children is not established.

Route & Dosage

Hypertension Adult: PO 10–20 mg daily, may increase to 40–80 mg/d

Administration

Oral

• Discontinue by reducing the dose gradually over 1 to 2 wk.

Adverse Effects (≥1%)

CNS: Dizziness, fatigue, headache, insomnia. CV: AV block, bradycardia. GI: Nausea, diarrhea, dyspepsia. Respiratory: Cough, dyspnea. Urogenital: Impotence.

Interactions

Drug: diuretics and other hypotensive agents increase hypotensive effect; effects of albuterol, metaproterenol, terbutaline, pirbuterol, and penbutolol are antagonized; nsaids blunt hypotensive effect; decreases hypoglycemic effect of glyburide; amiodarone increases risk of bradycardia and sinus arrest.

Pharmacokinetics

Absorption: Readily from GI tract. Peak: 2–3 h. Duration: 20 h. Metabolism: In liver. Elimination: In urine. Half-Life: 5 h.

Nursing Implications

Assessment & Drug Effects

• Take apical pulse before administering drug. If pulse is below 60, or other established parameter, hold the drug and contact physician.
• Take a BP reading before giving drug, if BP is not stabilized. If systolic pressure is ≤90 mm Hg, hold drug and contact physician.
• Check BP near end of dosage interval or before administration of next dose to evaluate effectiveness.
• Monitor therapeutic effectiveness. Full effectiveness of the drug may not be seen for 4–6 wk.
• Watch for S&S of bronchial constriction. Report promptly and withhold drug.
• Monitor diabetics for loss of glycemic control. Drug suppresses clinical signs of hypoglycemia (e.g., BP changes, increased pulse rate) and may prolong hypoglycemic state.
• Monitor carefully for exacerbation of angina during drug withdrawal.

Patient & Family Education

• Do not discontinue the drug without physician's advice because of the possible exacerbation of ischemic heart disease.
• If diabetic, report persistent S&S of hypoglycemia (see Appendix F) to physician (diabetics).
• Avoid driving or other potentially hazardous activities until response to drug is known.
• Make position changes slowly and avoid prolonged standing. Notify physician if dizziness and light-headedness persist.
• Comply with and do not alter established regimen (i.e., do not omit, increase, or decrease dosage or change dosage interval).
• Avoid prolonged exposure of extremities to cold.
• Avoid excesses of alcohol. Heavy alcohol consumption [i.e., >60 mL (2 oz)/d] may elevate arterial pressure; therefore, to maintain treatment effectiveness, either avoid alcohol or drink moderately (<60 mL/d). Consult physician.

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Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug