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Pronunciation: la-BAYT-a-lol HYE-droe-KLOR-ide
Class: Alpha-adrenergic blocker, Beta-adrenergic blocker
- Injection 5 mg/mL
- Tablets 100 mg
- Tablets 200 mg
- Tablets 300 mg
Selectively blocks alpha-1 receptors and nonselectively blocks beta receptors to decrease BP, heart rate, and myocardial oxygen demand.
Completely absorbed from the GI tract. T max is 1 to 2 h. Relative bioavailability is 100% (oral and IV). Absolute bioavailability for oral compared with IV is 25%. Absolute bioavailability increases when administered with food. Steady-state levels are reached by approximately the third day of dosing.
Crosses the placental barrier. Approximately 50% protein bound.
Mainly through conjugation to glucuronide metabolites.
Plasma half-life is 6 to 8 h (not altered in patients with decreased hepatic or renal function). Metabolites excreted in urine and via the bile into the feces. Approximately 55% to 60% appears in urine as conjugates or unchanged labetalol within 24 h. Neither hemodialysis nor peritoneal dialysis removes a significant amount of labetalol from the general circulation.
2 to 4 h.
Lasting at least 8 h following single oral dose of 100 mg and more than 12 h after a 300 mg dose.
Elimination is reduced; lower maintenance dosage is generally required in elderly patients.
Indications and Usage
Management of hypertension.
Treatment of pheochromocytoma; management of clonidine-withdrawal hypertension.
Bronchial asthma; overt cardiac failure; greater than first-degree heart block; cardiogenic shock; severe bradycardia; conditions associated with severe and prolonged hypotension; history of obstructive airway disease, including asthma; hypersensitivity to any component of the product.
Dosage and AdministrationAdults
PO Start with 100 mg twice daily. After 2 or 3 days, using standing BP as an indicator, the dosage may be titrated in increments of 100 mg twice daily every 2 or 3 days. Usual maintenance dosage is 200 to 400 mg twice daily. IV 20 mg over 2 min; then 40 or 80 mg every 10 min up to max of 300 mg. Infusions of 2 mg/min can be initiated and titrated to response.
- Administer 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 daily.
- Keep patient supine during IV administration and for 3 h afterward.
- Labetalol is compatible with following parenteral solutions: Ringer's, lactated Ringer's, dextrose 5% and Ringer's, lactated Ringer's 5% and dextrose 5%, dextrose 5%, sodium chloride 0.9%, dextrose 5% and sodium chloride 0.2%, dextrose 2.5% and sodium chloride 0.45%, dextrose 5% and sodium chloride 0.9%, and dextrose 5% and sodium chloride 0.33%.
- Do not freeze injection vials. Protect from light. Parenteral solution is stable for 24 h after dilution.
Store tablets between 36° and 86°F. Protect from excessive moisture. Store injection between 36° and 86°F. After dilution, the parenteral solution is stable for 24 h refrigerated or at room temperature. Protect from freezing. Protect from light.
Drug InteractionsBeta-adrenergic agonists
Blunted bronchodilator effect.Cimetidine
Increased bioavailability of labetalol.Digitalis
Concomitant use may increase the risk of bradycardia.Diuretics
Additive antihypertensive effect may occur. When used therapeutically, be prepared to adjust the labetalol dosage as needed.Inhalation anesthetics
May exaggerate hypotension.Nitroglycerin
Increased hypotension.Tricyclic antidepressants
Bioavailability may be increased, increasing the adverse effects.
Injection not compatible with sodium bicarbonate 5%.
Laboratory Test Interactions
False-positive tests for urinary amphetamines; false-positive increases in levels of urinary catecholamines, metanephrine, normetanephrine, and vanillymandelic acid.
Edema, postural hypotension (1%); bradycardia, heart block, hypotension, syncope.
Dizziness (16%); fatigue (10%); paresthesia often described as scalp tingling (5%); headache (2%); asthenia (1%).
Rash (1%); alopecia, bullous lichen planus, facial erythema, generalized maculopapular rash, lichenoid rash, Peyronie disease, pruritus, psoriasiform rash, urticaria.
Nasal stuffiness (6%); vertigo (2%); abnormal vision (1%); dry eyes.
Nausea (19%); dyspepsia (4%); vomiting (3%); taste distortion (1%).
Ejaculation failure (5%); impotence (4%); difficulty in micturition including urinary bladder retention.
Cholestatic jaundice, elevated liver function tests, hepatic necrosis, hepatitis.
Anaphylactoid reactions, angioedema.
Reversible increases in serum transaminases (4%).
Muscle cramps, toxic myopathy.
Dyspnea (2%); bronchospasm.
Edema (2%); antimitochondrial antibodies, fever, positive antinuclear factor, SLE.
Monitor BP to determine response to parenterally administered labetalol.
Category C .
Excreted in breast milk.
Safety and efficacy not established.
Use with caution because drug metabolism may be impaired.
Special Risk Patients
Use with caution in patients with diabetes mellitus, CHF, respiratory difficulties, or severely elevated BP, or with nonallergic bronchospasm (eg, chronic bronchitis, emphysema).
Cardiac failure has been observed in patients with or without history.
Diabetes mellitus and hypoglycemia
Labetalol may prevent the appearance of premonitory signs and symptoms (eg, tachycardia) of acute hypoglycemia.
Rarely, severe hepatocellular injury may occur.
Protracted severe hypotension and difficulty in restarting or maintaining a heartbeat has been reported with beta-blockers.
Use with caution in patients with pheochromocytoma because paradoxical hypertension may occur in some patients.
Do not discontinue abruptly. Abrupt discontinuation may worsen angina and precipitate ischemic event in susceptible patients.
Bronchospasm, cardiac failure, excessive bradycardia, excessive orthostatic hypotension, seizures.
- Caution patient to avoid sudden position changes to prevent orthostatic hypotension. Advise use of support hose.
- Advise patient to notify dentist and other health care providers of drug therapy before treatment or surgery.
- Caution diabetic patient to monitor serum glucose carefully.
- Instruct patient to not discontinue drug abruptly.
- Advise patient to carry medical identification (eg, card, bracelet) indicating medical condition and drug regimen.
- Instruct patient how to measure BP and pulse.
- Emphasize importance of the following 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 health care provider: confusion, dizziness, fatigue, fever or depression, shortness of breath, slow heart rate, swelling of ankles and feet.
- Advise patient that drug causes dizziness and to use caution while driving or performing other tasks requiring mental alertness.
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