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Trade Names:
Trandate
- Tablets 100 mg
- Tablets 200 mg
- Tablets 300 mg
- Injection 5 mg/mL

Mechanism of Action

Pharmacology

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

Pharmacokinetics

Absorption

Completely absorbed from the GI tract. T _max is 1 to 2 h. Relative bioavailability is 100% (oral and solution). Absolute bioavailability for oral compared with IV is 25%. Absolute bioavailability increases when administered with food. Steady-state levels are reached by about the third day of dosing.

Distribution

Crosses the placental barrier. Approximately 50% protein bound.

Metabolism

Mainly though conjugation to glucuronide metabolites.

Elimination

Plasma t _½ is 6 to 8 h (not altered in patient 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.

Peak

2 to 4 h.

Duration

Lasting at least 8 h following single oral dose of 100 mg and more than 12 h after a 300 mg dose.

Special Populations

Elimination is reduced; lower maintenance dosage is generally required in elderly.

Indications and Usage

Management of hypertension.

Unlabeled Uses

Treatment of pheochromocytoma; management of clonidine-withdrawal hypertension.

Contraindications

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

Dosage and Administration

PO 100 mg twice daily initially; maintenance dose usually 200 to 400 mg twice daily. IV 20 mg over 2 min; then 40 to 80 mg every 10 min up to max of 300 mg. Infusions of 2 mg/min can be initiated and titrated to response.

General Advice

• Tablets
• 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/day.

• Injection
• 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.

Storage/Stability

Store at controlled temperature (59° to 86°F).

Store injection in refrigerator at controlled room temperature (59° to 86°F). Protect from light. Parenteral solution is stable for 24 h after dilution.

Drug Interactions

Blunted bronchodilator effect.

Increased bioavailability of labetalol.

Impaired antihypertensive effect of labetalol.

May exaggerate hypotension.

Increased hypotension.

Incompatibility

Injection not compatible with sodium bicarbonate 5%.

Laboratory Test Interactions

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

Adverse Reactions

Cardiovascular

Orthostatic hypotension; edema; flushing; ventricular arrhythmias; AV block; bradycardia; heart failure; chest pain.

CNS

Headache; fatigue; dizziness; depression; lethargy; drowsiness; forgetfulness; sleepiness; vertigo; paresthesia; nightmares.

Dermatologic

Tingling of scalp; rash; facial erythema; alopecia; urticaria; pruritus; increased sweating.

EENT

Dry eyes; visual disturbances; altered taste perception.

GI

Nausea; vomiting; diarrhea; dyspepsia.

Genitourinary

Impotence; urinary retention; difficulty with urination; failure to ejaculate; priapism; Peyronie disease.

Hematologic

Leukopenia.

Hepatic

Elevated transaminases; jaundice; cholestasis.

Metabolic

Increases or decreases in serum glucose; increased creatinine and BUN.

Respiratory

Bronchospasm; shortness of breath; wheezing.

Miscellaneous

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 with caution in patients with diabetes mellitus, CHF, respiratory difficulties, or severely elevated BP.

Cardiac failure

Cardiac failure has been observed in patients with or without history.

Withdrawal

Do not discontinue abruptly. Abrupt discontinuation may worsen angina and precipitate ischemic event in susceptible individuals.

Overdosage

Symptoms

Excessive orthostatic hypotension, excessive bradycardia, cardiac failure, bronchospasm, seizures.

Patient Information

• 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: 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.