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

[ləbet′əlol]

an antihypertensive drug with beta and alpha blocking properties.

indications It is prescribed for the treatment of moderate to severe hypertension.

contraindications The presence of asthma or emphysema prohibits its use. It should be used with caution in patients with diabetes because it may mask symptoms of hypoglycemia, particularly tachycardia.

adverse effects Among the most serious adverse effects are orthostatic hypotension, fatigue, headache, skin rashes, scalp paresthesia, nausea, and vomiting.

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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.