labetalol hydrochloride

la·bet·a·lol hydrochloride (l-bt-lôl, -ll)

n.

An alpha- and beta-blocker that is used in the treatment of hypertension.

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labetalol hydrochloride Warning - High-alert drug!

Trandate

Pharmacologic class: Beta-adrenergic blocker (nonselective), alpha-adrenergic blocker (selective)

Therapeutic class: Antihypertensive

Pregnancy risk category C

Action

Blocks stimulation of beta₁- and beta₂-adrenergic receptor sites and alpha₁-adrenergic receptors, decreasing myocardial contractile force and enhancing coronary artery blood flow and myocardial perfusion. Net effect is decreased heart rate and blood pressure.

Availability

Injection: 5 mg/ml

Tablets: 100 mg, 200 mg, 300 mg

⊘Indications and dosages

➣ Hypertension

Adults: Initially, 100 mg P.O. b.i.d., alone or combined with a diuretic; may increase by 100 mg b.i.d. q 2 to 3 days as needed. Usual range is 400 to 800 mg/day in two divided doses; up to 2.4 g/day have been given.

➣ Hypertensive crisis

Adults: Initially, 20 mg I.V. bolus over 2 minutes, then I.V. injection of 40 to 80 mg q 10 minutes until blood pressure falls to desired level; maximum dosage is 300 mg. Alternatively, 50 to 200 mg by continuous I.V. infusion at 2 mg/minute; continue infusion until desired blood pressure is reached. Follow I.V. dosing with P.O. dosing.

➣ Conversion from I.V. to P.O. dosing

Hospitalized adults: Discontinue I.V. therapy when desired blood pressure is reached; start P.O. dosing when supine diastolic pressure begins to rise. Initial P.O. dosage is 200 mg, followed 6 to 12 hours later with additional dose of 200 to 400 mg P.O., depending on blood pressure response. Then titrate at 1-day intervals to dosage ranging from 400 to 2,400 mg/day P.O. in two or three divided doses.

Dosage adjustment

• Chronic hepatic disease
• Elderly patients

Off-label uses

• Hypertension secondary to pheochromocytoma or clonidine withdrawal

Contraindications

• Hypersensitivity to drug
• Bronchospastic disease
• Overt heart failure, cardiogenic shock
• Second- or third-degree atrioventricular block
• Severe bradycardia
• Conditions associated with severe and prolonged hypotension

Precautions

Use cautiously in:
• hepatic impairment, pulmonary disease, diabetes mellitus, hyperthyroidism, thyrotoxicosis
• elderly patients
• pregnant or breastfeeding patients
• children.

Administration

• Know that drug may be given as I.V. bolus or continuous infusion.
• Be aware that drug may be given undiluted for I.V. bolus injection. For continuous infusion, dilute in dextrose 5% in water or normal saline solution, and deliver with infusion control pump.
• Don't mix with 5% sodium bicarbonate injection.
• Give direct I.V. injection over 2 minutes at 10-minute intervals.

Route	Onset	Peak	Duration
P.O.	20 min-2 hr	1-4 hr	8-12 hr
I.V.	2-5 min	5 min	16-18 hr

Adverse reactions

CNS: fatigue, asthenia, anxiety, depression, dizziness, paresthesia, drowsiness, insomnia, memory loss, nightmares, mental status changes

CV: orthostatic hypotension, peripheral vasoconstriction, bradycardia, arrhythmias, heart failure

EENT: blurred vision, dry eyes, nasal congestion

GI: nausea, diarrhea, constipation

GU: erectile dysfunction, decreased libido

Hematologic: purpura, agranulocytosis, thrombocytopenia

Metabolic: hyperglycemia, hypoglycemia

Musculoskeletal: joint pain, back pain, muscle cramps

Respiratory: wheezing, bronchospasm, pulmonary edema

Skin: rash, pruritus

Interactions

Drug-drug. Adrenergic bronchodilators, theophylline: decreased efficacy of these drugs

Antihypertensives, nitrates: additive hypotension

Cimetidine, propranolol: increased labetalol effects

Digoxin: additive bradycardia

Dobutamine, dopamine: reduced beneficial cardiovascular effects of these drugs

General anesthetics, verapamil: additive myocardial depression

Insulin, oral hypoglycemics: altered hypoglycemic efficacy

MAO inhibitors: hypertension

Nonsteroidal anti-inflammatory drugs: decreased antihypertensive action

Drug-diagnostic tests. Alanine aminotransferase, alkaline phosphatase, antinuclear antibodies, aspartate aminotransferase, blood urea nitrogen, glucose, liver function tests, low-density lipoproteins, potassium, triglycerides, uric acid: increased values

Patient monitoring

• Monitor ECG and vital signs, especially blood pressure.
• Assess cardiovascular, respiratory, and neurologic status closely to detect adverse reactions.
• Monitor CBC, blood glucose level, and liver function tests.

Patient teaching

☞ Instruct patient to immediately report adverse reactions, such as easy bruising or bleeding or respiratory problems.
• Tell patient he may feel dizzy when starting therapy, especially if he's also taking a diuretic.
• Advise patient to move slowly when sitting up or standing, to avoid dizziness or light-headedness from sudden blood pressure decrease.
• Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration, vision, and alertness.
• Emphasize need for follow-up care and regular blood pressure monitoring.
☞ Caution patient not to stop taking drug abruptly, because this may cause myocardial infarction or worsen angina.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.