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Labet Injection

Pharmacology/Description

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.

 

Indication

1. The control of all grades of hypertension including pregnancy-induced hypertension 2. The treatment of angina in patients with hypertension 3. Where a hypertensive technique is indicated in anesthesia 4. The management of catecholamine excess and patients with pheochromocytoma.

 

Dosage And Administration

Adults: Bolus Injection: If it is essential to reduce the blood pressure quickly a dose of 50 mg should be given by intravenous injection (over a period of at least one minute) and, if necessary, repeated at five minute intervals until a satisfactory response occurs. The total dose should not exceed 200 mg. Intravenous Infusion: For intravenous infusion the injection should be diluted with a suitable intravenous infusion fluid to a concentration of Labetalol Hydrochloride 1 mg/1 ml. Compatible fluids include 5% Dextrose; 0.9% Sodium Chloride; Dextrose and Sodium Chloride. Hypertension in pregnancy: Infusion should be started at 20 mg/hour, then doubled every 30 minutes until a satisfactory response is obtained or a dosage of 160 mg/hour is reached. Hypertensive episodes following acute myocardial infarction: Infusion should be started at 15 mg/hour and gradually increased to a maximum of 120 mg/hour depending on the control of blood pressure. Hypertension due to other causes: Infuse at a rate of about 2 mg/min until a satisfactory response is obtained, then stop infusion. The effective dose is usually 50-200 mg but larger doses may be needed, especially in patients with phaeochromocytoma. The rate of infusion may be adjusted according to the response at the discretion of the physician. Labetalol injection has been administered to patients with uncontrolled hypertension already receiving other hypotensive agents, including b-blocking drugs, without adverse effects. Hypotensive anaesthesia: Induction should be with standard agents (e.g. sodium thiopentone) and anaesthesia maintained with nitrous oxide and oxygen with or without halothane. The recommended starting dose of Labetalol injection is 10-20 mg intravenously depending on the age and condition of the patient. Patients for whom halothane is contraindicated usually require a higher initial dose of Labetalol (25-30 mg). If satisfactory hypotension is not achieved after five minutes, increments of 5-10 mg should be given until the desired level of blood pressure is attained. Halothane and Labetalol act synergistically therefore the halothane concentration should not exceed 1-1.5% as profound falls in blood pressure may be precipitated. Children: Safety and efficacy in children have not been established.

 

Side Effects

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.

 

Contraindications

Labetalol injection is contraindicated in second or third degree heart block, cardiogenic shock and other conditions associated with severe and prolonged hypotension or severe bradycardia. When peripheral vasoconstriction suggests low cardiac output, the use of Labetalol injection to control hypertensive episodes following acute myocardial infarction is contraindicated. Beta-blockers, even those with apparent cardioselectivity, should not be used in patients with asthma or a history of obstructive airways disease. Labetalol is contraindicated for patients known to have hypersensitivity to the medicine.

 

Drug Interactions

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. Labetalol may enhance digoxin\’s effect of reducing ventricular rate. Concomitant administration of Labetalol with adrenaline may result in bradycardia and hypertension.

 

Precautions

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. If the patient develops symptomatic bradycardia, then the dosage of Labetalol should be reduced. Use in Pregnancy: Labetalol should only be used during the first trimester of pregnancy if the potential benefit outweighs the potential risk. Use in Lactation: Labetalol is excreted in breast milk in small amounts. Caution should be exercised when Labetalol is administered to breast feeding women.

 

Over Dosage

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 b2-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 the 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. Transvenous pacing may be required. Haemodialysis removes less than 1% Labetalol hydrochloride from the circulation.

 

Pharmaceutical Precautions

Store in cool dry place protected from light. Keep out of reach of children.

 

Commercial Pack

LabetTM IV injection: Each box contains 1 ampoule.

Product Description

Labetalol injection 50mg/10ml