Labetalol Hydrochloride (Injection)

• Severe hypertension

Labetalol Injection is indicated in Hypertension (including hypertension in pregnancy, hypertension after stroke, hypertension with angina, and hypertension following acute myocardial infarction); hypertensive crisis; Anaesthesia when a hypotensive technique is indicated.

N/A

Labetalol is contraindicated for patients known to have hypersensitivity to the medicine. Labetalol is contraindicated in second or third degree heart block, infranodal A-V block, uncontrolled heart failure, sick-sinus syndrome, cardiogenic shock and other conditions associated with severe and prolonged hypotension or severe bradycardia, and bronchial asthma or other obstructive lung disorders.

Labetalol is a competitive antagonist at b1 and b2 adrenoreceptors and has some intrinsic activity at b2 adrenoreceptors. Labetalol has, in addition to its b-blocking action, a competitive antagonist action at postsynaptic a-adrenoreceptors. In isolated tissues Labetalol is four to eight times more potent at b than a-adrenoreceptors.

Labetalol may enhance the hypotensive effects of halothane. Care should be taken if labetalol is used concomitantly with either Class I antiarrhythmic agents or calcium antagonists of the verapamil type. The hypotensive effect of Labetalol may be reduced when used in combination with prostaglandin synthetase inhibitors (NSAIDs). Dosage adjustments may therefore be necessary. Concomitant use of tricyclic antidepressants may increase the incidence of tremor. Cimetidine may increase the bioavailability of Labetalol and care is required in oral dosing of the latter.

Adverse effects reported are postural hypotension (avoid upright position during and for 3 hours after intravenous administration), tiredness, weakness, headache, rashes, scalp tingling, difficulty in micturition, epigastric pain, nausea, vomiting; liver damage.

Profound cardiovascular effects are to be expected, e.g. excessive, posture-sensitive hypotension and sometimes bradycardia. Patients should be laid supine with the legs raised. Use a cardiac glycoside and a diuretic in cardiac failure; for bronchospasm, administer a b 2 -agonist per aerosol. Intravenous atropine 0.25 to 3 mg should be given to relieve bradycardia. Intravenous noradrenaline 5 to 10 mg initially, repeated according to response may be preferable to isoprenaline to improve circulation. Alternatively, noradrenaline may be infused at a rate of 5 mg per minute until the response is satisfactory. In severe overdose, intravenous glucagon may be preferred: an initial bolus dose of 5 to 10 mg in dextrose or saline should be followed by an intravenous infusion of 5 mg/hour or as sufficient to maintain cardiac output.

Labetalol should only be used during the first trimester of pregnancy if the potential benefit outweighs the potential risk. Labetalol is excreted in breast milk in small amounts. Caution should be exercised when labetalol is administered to breast feeding women.

There have been rare reports of severe hepatocellular injury with Labetalol therapy. The hepatic injury is usually reversible and has occurred after both short and long term treatment. If there is laboratory evidence of liver injury or the patient is jaundiced, Labetalol therapy should be stopped and not re-started. Particular care should be taken when Labetalol is to be used in patients with hepatic impairment. Labetalol should be used with caution in patients with peripheral vascular disease as their symptoms may be exacerbated.