Labetalol hydrochloride
Labetalol hydrochloride (Normodyne, Trandate)
Labetalol hydrochloride
(lah- BET-ah-lohl)
Pregnancy Category: C Normodyne Trandate (Rx)

Classification: Alpha- and beta-adrenergic blocking agent

See Also: See also Beta-Adrenergic Blocking Agents and Antihypertensive Agents .

Action/Kinetics: Decreases BP by blocking both alpha- and beta-adrenergic receptors. Standing BP is lowered more than supine. Significant reflex tachycardia and bradycardia do not occur although AV conduction may be prolonged. Onset: PO, 2-4 hr; IV, 5 min. Peak plasma levels, PO: 1-2 hr. Peak effects, PO: 2-4 hr. Duration: PO, 8-12 hr. t 1/2: PO, 6-8 hr; IV, 5.5 hr. Significant first-pass effect; metabolized in liver. Food increases bioavailability of the drug.

Uses: PO: Alone or in combination with other drugs for hypertension. IV: Hypertensive emergencies. Investigational: Pheochromocytoma, clonidine withdrawal hypertension.

Contraindications: Cardiogenic shock, cardiac failure, bronchial asthma, bradycardia, greater than first-degree heart block.

Special Concerns: Use with caution during lactation, in impaired renal and hepatic function, in chronic bronchitis and emphysema, and in diabetes (may prevent premonitory signs of acute hypoglycemia). Safety and efficacy in children have not been established.

Side Effects: See also Beta-Adrenergic Blocking Agents. After PO Use. GI: Diarrhea, cholestasis with or without jaundice. CNS: Fatigue, drowsiness, paresthesias, headache, syncope (rare). GU: Impotence, priapism, ejaculation failure, difficulty in micturition, Peyronie's disease, acute urinary bladder retention. Respiratory: Dyspnea, bronchospasm. Musculoskeletal: Muscle cramps, asthenia, toxic myopathy. Dermatologic: Generalized maculopapular, lichenoid, or urticarial rashes; bullous lichen planus, psoriasis, facial erythema, reversible alopecia. Ophthalmic: Abnormal vision, dry eyes. Miscellaneous: SLE, positive antinuclear factor, antimitochondrial antibiodies, fever, edema, nasal stuffiness.
After parenteral use. CV: Ventricular arrhythmias. CNS: Numbness, somnolence, yawning. Miscellaneous: Pruritus, flushing, wheezing.
After PO or parenteral use. GI: N&V;, dyspepsia, taste distortion. CNS: Dizziness, tingling of skin or scalp, vertigo. Miscellaneous: Postural hypotension, increased sweating.

Laboratory Test Alterations: False + increase in urinary catecholamines. Transient serum transaminases, BUN, serum creatinine.

Overdose Management: Symptoms: Excessive hypotension and bradycardia. Treatment: Induce vomiting or perform gastric lavage. Place clients in a supine position with legs elevated. If required, the following treatment can be used: Epinephrine or a beta-2 agonist (aerosol) to treat bronchospasm. Atropine or epinephrine to treat bradycardia. Digitalis glycoside and a diuretic for cardiac failure; dopamine or dobutamine may also be used. Diazepam to treat seizures. Norepinephrine (or another vasopressor) to treat hypotension. Administration of glucagon (5-10 mg rapidly over 30 sec), followed by continuous infusion of 5 mg/hr, may be effective in treating severe hypotension and bradycardia.

Drug Interactions: Beta-adrenergic bronchodilators / Bronchodilator drug effects Cimetidine / Bioavailability of PO labetalol Glutethimide / Labetalol effects R/T liver breakdown Halothane / Risk of severe myocardial depression hypotension Nitroglycerin / Additive hypotension Tricyclic antidepressants / Risk of tremors

How Supplied: Injection: 5 mg/mL; Tablet: 100 mg, 200 mg, 300 mg

Dosage
?Tablets Hypertension.
Individualize. Initial: 100 mg b.i.d. alone or with a diuretic; maintenance: 200-400 mg b.i.d. up to 1,200-2,400 mg/day for severe cases.
?IV Hypertension.
Individualize. Initial: 20 mg slowly over 2 min; then, 40-80 mg q 10 min until desired effect occurs or a total of 300 mg has been given.
?IV Infusion Hypertension.
Initial: 2 mg/min; then, adjust rate according to response. Usual dose range: 50-300 mg.
Transfer from IV to PO therapy.
Initial: 200 mg; then, 200-400 mg 6-12 hr later, depending on response. Thereafter, dosage based on response.