Labetalol

Intravenous
Emergency treatment of hypertension

Intravenous
Hypotensive anaesthesia

Intravenous
Hypertension after myocardial infarction

Intravenous
Hypertension in pregnancy

Oral
Hypertension

Should be taken with food. Take immediately after meals.

Na bicarbonate 5% and alkaline solutions.

Obstructive airway disease (e.g. bronchial asthma), 2nd and 3rd degree heart block, cardiogenic shock, conditions w/ severe or prolonged hypotension, uncompensated heart failure, severe bradycardia.

Patients w/ phaeochromocytoma, inadequate cardiac function and well-compensated heart failure, DM, nonallergic bronchospasm. Patients undergoing major surgery involving general anaesth. May mask symptoms of hypoglycaemia. Avoid abrupt withdrawal as it may exacerbate angina. Hepatic impairment. Elderly, pregnancy and lactation.

Intraoperative floppy iris syndrome, orthostatic hypotension, bradycardia, syncope, paraesthesia, dizziness, dyspnoea, fatigue, vertigo, headache, nasal stuffiness, diarrhoea, abdominal pain, male sexual dysfunction, dyspepsia, nausea, vomiting, flatulence, constipation, taste disturbances, scalp tingling, tremor, muscle weakness, urinary retention, hepatitis, jaundice, rash, increased transaminases, nightmares, claudication.
Potentially Fatal: Hepatic injury.

IV/Parenteral/PO: C

Monitor LFT periodically and BP.

Symptoms: Hypotension, bradycardia, cardiac failure, bronchospasm. Management: Symptomatic and supportive treatment. Admin activated charcoal after emesis or gastric lavage. Atropine or epinephrine may be given for bradycardia. For severe hypotension, a vasopressor (e.g. dopamine, norepinephrine) may be administered and for heart failure, a cardiac glycoside and diuretic. Glucagon may be beneficial for the management of myocardial depression and hypotension. A β2-adrenergic agonist and/or a theophylline derivative may be used for bronchospasm. Diazepam may be used for seizures.

Synergistic hypotensive effect w/ halothane. Increased absolute bioavailability w/ cimetidine. Decreased absolute bioavailability w/ glutethimide. Additive hypotensive effect w/ nitroglycerin. Increased incidence of tremor w/ TCAs. Increased risk of bradycardia and heart block w/ Ca channel blocker (e.g. verapamil, diltiazem).

False-positive results in fluorometric or photometric analysis of urinary catecholamines.

Description: Labetalol competitively inhibits the adrenergic stimulation of β-receptors w/in the myocardium, bronchial and vascular smooth muscle, and α1-receptors w/in vascular smooth muscle. It also has some intrinsic β2-agonist and membrane-stabilising activity.
Onset: 20 min to 2 hr (oral); 2-5 min (IV).
Duration: Dose dependent: 8-12 hr (oral); 2-18 hr (IV).
Pharmacokinetics:
Absorption: Absorbed readily from the GI tract. Bioavailability increased by food. Time to peak plasma concentration: Approx 1-2 hr (oral); 5-15 min (IV).
Distribution: Crosses the placenta, enters breast milk. Volume of distribution: 3-16 L/kg. Plasma protein binding: Approx 50%.
Metabolism: Extensive first-pass metabolism primarily via glucuronide conjugation.
Excretion: Via urine (55-60% as glucuronide conjugates; <5% as unchanged drug). Elimination half-life: Approx 6-8 hr (oral); approx 5.5 hr (IV).

Store between 2-30°C.

Beta-Blockers

Anon. Labetalol. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 26/11/2013.

Buckingham R (ed). Labetalol Hydrochloride. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 26/11/2013.

Joint Formulary Committee. Labetalol Hydrochloride. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 26/11/2013.

Labetalol HCl Tab, Film-Coated (Par Pharmaceutical Companies, Inc). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 26/11/2013.

Labetalol Injection (Sagent Pharmaceuticals). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 26/11/2013.

McEvoy GK, Snow EK, Miller J et al (eds). Labetalol Hydrochloride. AHFS Drug Information (AHFS DI) [online]. American Society of Health-System Pharmacists (ASHP). https://www.medicinescomplete.com. Accessed 26/11/2013.

Trandate Tablets and Injection. U.S. FDA. https://www.fda.gov/. Accessed 26/11/2013.