Labetalol HCL

A to Z Drug Facts

 Action Selectively blocks alpha-1 receptors and nonselectively blocks beta-receptors to decrease BP, heart rate and myocardial oxygen demand.

 Indications Management of hypertension. Unlabeled use(s): Treatment of pheochromocytoma; management of clonidine-withdrawal hypertension.

 Contraindications Severe bradycardia; second- and third-degree heart block; heart failure; cardiogenic shock; bronchial asthma.

 Route/Dosage

ADULTS: PO 100 mg bid initially; maintenance dose usually 200 to 400 mg bid. IV 20 mg over 2 min; then 40 to 80 mg q 10 min up to maximum of 300 mg. Infusions of 2 mg/min can be initiated and titrated to response.

 Interactions

Beta-adrenergic agonists: Blunted bronchodilator effect. Cimetidine: Increased bioavailability of labetalol. Indomethacin: Impaired antihypertensive effect of labetalol. Inhalation anesthetics: May exaggerate hypotension. Nitroglycerin: Increased hypotension. INCOMPATABILITIES: Injection not compatible with 5% sodium bicarbonate.

 Lab Test Interferences Drug may cause false-positive increases in levels of urinary catecholamines.

 Adverse Reactions

CV: Orthostatic hypotension; edema; flushing; ventricular arrhythmias; atrioventricular block; bradycardia; heart failure; chest pain. CNS: Headache; fatigue; dizziness; depression; lethargy; drowsiness; forgetfulness; sleepiness; vertigo; paresthesias; nightmares. DERM: Tingling of scalp; rash; facial erythema; alopecia; urticaria; pruritus; increased sweating. EENT: Dry eyes; visual disturbances; altered taste perception. GI: Nausea; vomiting; diarrhea; dyspepsia. GU: Impotence; urinary retention; difficulty with urination; failure to ejaculate; priapism; Peyronie's disease. HEMA: Leukopenia. HEPA: Elevated transaminases; jaundice; cholestasis. META: Increases or decreases in serum glucose; increased creatinine and BUN. RESP: Bronchospasm; shortness of breath; wheezing. OTHER: Muscle cramps; systemic lupus erythematosus; increased hypoglycemic response to insulin; masking of hypoglycemic signs; asthenia.

 Precautions

Pregnancy: Category C. Lactation: Excreted in breast milk. Children: Safety and efficacy not established. Special risk patients: Use drug with caution in patients with diabetes mellitus, CHF, respiratory difficulties or severely elevated BP. Cardiac failure: Has been observed in patients with or without history of cardiac failure. Withdrawal: Do not discontinue abruptly. Abrupt discontinuation may worsen angina and precipitate ischemic event in susceptible individuals.

 Administration/Storage

• Administer oral form with food. Tablets can be crushed.
• If nausea and dizziness occur with twice daily dosing of oral form, same total daily dose can be administered as divided doses 3 times/day.
• Keep patient supine during IV administration and for 3 hr afterward.
• For repeated IV injection, give 20 mg dose slowly over 2 min.
• For slow continuous infusion, dilute contents with compatible IV fluid and administer at rate of 2 mg/min. Use controlled administration device. Once satisfactory response is obtained, infusion can be discontinued and treatment with oral labetalol can be initiated.
• Labetalol is compatible with following parenteral solutions: Ringer's, lactated Ringer's 5% Dextrose and Ringer's, 5% lactated Ringer's and 5% Dextrose, 5% Dextrose, 0.9% Sodium Chloride, 5% Dextrose and 0.2% Sodium Chloride, 2.5% Dextrose and 0.45% Sodium Chloride, 5% Dextrose and 0.9% Sodium Chloride and 5% Dextrose and 0.33% Sodium Chloride.
• Store at room temperature and protect from excessive moisture.
• Do not freeze injection vials. Protect from light. Parenteral solution is stable for 24 hr after dilution.

 Assessment/Interventions

• Obtain patient history, including drug history and any known allergies.
• Measure vital signs and supine BP immediately before and at 5 to 10 min intervals after direct IV injection.
• Obtain renal and liver studies before therapy begins.
• Take safety precautions if orthostatic hypotension occurs.
• Closely monitor diabetic patients for signs of hypoglycemia.
• Assess skin turgor and dryness of mucous membranes for hydration status.

 Patient/Family Education

• Caution patient to avoid sudden position changes to prevent orthostatic hypotension. Advise use of support hose.
• Advise patient to notify dentist and other physicians of drug therapy before treatment or surgery.
• Caution diabetic patient to monitor serum glucose carefully.
• Instruct pa4ient nod to discontinue drug abruptly.
• Advise patient to carry identification (eg, Medi-Alert) indicating medical condition and drug regimen.
• Instruct patient how to measure BP and pulse.
• Emphasize importance of other modalities on BP: Weight control, regular exercise, smoking cessation and moderate intake of alcohol and salt.
• Inform patient that transient scalp tingling may occur, especially when treatment is initiated.
• Instruct patient to report the following symptoms to physician: Slow heart rate, dizziness, confusion, fever or depression, shortness of breath, fatigue, swelling of ankles and feet.
• Advise patient that drug causes dizziness and to use caution while driving or performing other tasks requiring mental alertness.
• Instruct patient not to take any otc medications without consulting physician.

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