a/b-blockers (alpha-blockers / beta-blockers).

Labetalol - hypertension

Labetalol hydrochloride 5mg/ml.

Solution for Injection

Trandate Injection is indicated for the treatment of:- 1. Severe hypertension, including severe hypertension of pregnancy, when rapid control of blood pressure is essential. 2. Anaesthesia when a hypotensive technique is indicated. 3. Hypertensive episodes following acute myocardial infarction

Adults:

Trandate Injection is intended for intravenous use in hospitalised patients. The plasma concentrations achieved after intravenous dose of Trandate in severe hypertension are substantially greater than those following oral administration of the drug and provide a greater degree of blockade of alpha-adrenoceptors necessary to control the more severe disease. Patients should, therefore, always receive the drug whilst in the supine or left lateral position. Raising the patient into the upright position, within three hours of intravenous Trandate administration, should be avoided since excessive postural hypotension may occur.

Bolus injection

If it is essential to reduce blood pressure quickly, as for example, in hypertensive encephalopathy, a dose of 50mg of Trandate should be given by intravenous injection over a period of at least one minute. If necessary, doses of 50mg may be repeated at five minute intervals until a satisfactory response occurs. The total dose should not exceed 200mg. After bolus injection, the maximum effect usually occurs within five minutes and the effective duration of action is usually about six hours but may be as long as eighteen hours.

Intravenous infusion

An alternative method of administering Trandate is intravenous infusion of a solution made by diluting the contents of two ampoules (200mg) to 200ml with Sodium Chloride and Dextrose Injection BP or 5% Dextrose Intravenous Infusion BP. The resultant infusion solution contains 1mg/ml of Trandate. It should be administered using a paediatric giving set fitted with a 50ml graduated burette to facilitate dosage.

In the hypertension of pregnancy: The infusion can be started at the rate of 20mg per hour and this dose may be doubled every thirty minutes until a satisfactory reduction in blood pressure has been obtained or a dosage of 160mg per hour is reached. Occasionally, higher doses may be necessary.

In hypertensive episodes following acute myocardial infarction: The infusion should be commenced at 15mg per hour and gradually increased to a maximum of 120mg per hour depending on the control of blood pressure.

In hypertension due to other causes: The rate of infusion of Trandate should be about 2mg (2ml of infusion solution) per minute, until a satisfactory response is obtained; the infusion should then be stopped. The effective dose is usually in the range of 50-200mg depending on the severity of the hypertension. For most patients it is unnecessary to administer more than 200mg but larger doses may be required especially in patients with phaeochromocytoma. The rate of infusion may be adjusted according to the response, at the discretion of the physician. The blood pressure and pulse rate should be monitored throughout the infusion.

It is desirable to monitor the heart rate after injection and during infusion. In most patients, there is a small decrease in the heart rate; severe bradycardia is unusual but may be controlled by injecting atropine 1-2 mg intravenously. Respiratory function should be observed particularly in patients with any known impairment.

Once the blood pressure has been adequately reduced, maintenance therapy with Trandate tablets should be instituted with a starting dose of one 100mg tablet twice daily (see Trandate tablets SmPC for further details). Trandate Injection has been administered to patients with uncontrolled hypertension already receiving other hypotensive agents, including beta-blocking drugs, without adverse effects.

In 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 Trandate Injection is 10-20mg intravenously depending on the age and condition of the patient. Patients for whom halothane is contra-indicated usually require a higher initial dose of Trandate (25-30mg). If satisfactory hypotension is not achieved after five minutes, increments of 5-10mg should be given until the desired level of blood pressure is attained.

Halothane and Trandate act synergistically therefore the halothane concentration should not exceed 1-1.5% as profound falls in blood pressure may be precipitated.

Following Trandate Injection the blood pressure can be quickly and easily adjusted by altering the halothane concentration and / or adjusting table tilt. The mean duration of hypotension following 20-25mg of Trandate is fifty minutes.

Hypotension induced by Trandate Injection is readily reversed by atropine 0.6mg and discontinuation of halothane.

Tubocurarine and pancuronium may be used when assisted or controlled ventilation is required. Intermittent Positive Pressure Ventilation (IPPV) may further increase the hypotension resulting from Trandate Injection and / or halothane

Safety and efficacy have not been established.

Initially 50 mg twice daily.

• Cardiogenic shock.

• Uncontrolled, incipient or digitalis refractory heart failure.

• Sick sinus syndrome (including sino-atrial block).

• Second or third degree heart block.

• Prinzmetal's angina.

• History of wheezing or asthma.

• Untreated phaeochromocytoma.

• Metabolic acidosis.

• Bradycardia (<45-50 bpm).

• Hypotension .

• Hypersensitivity to labetalol.

• Severe peripheral circulatory disturbances.

• Where peripheral vasoconstriction suggests low cardiac output, the use of Trandate Injection to control hypertensive episodes following acute myocardial infarction is contra-indicated.

There have been reports of skin rashes and/ or dry eyes associated with the use of beta-adrenoceptor blocking drugs. The reported incidence is small and in most cases the symptoms have cleared when the treatment was withdrawn. Gradual discontinuance of the drug should be considered if any such reaction is not otherwise explicable.

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. Appropriate laboratory testing should be done at the first sign or symptom of liver dysfunction. If there is laboratory evidence of liver injury or the patient is jaundiced, labetalol therapy should be stopped and not re-started.

Due to negative inotropic effects, special care should be taken with patients whose cardiac reserve is poor and heart failure should be controlled before starting Trandate therapy.

Patients particularly those with ischemic heart disease, should not interrupt/ discontinue abruptly Trandate therapy. The dosage should gradually be reduced, ie. over 1-2 weeks, if necessary at the same time initiating replacement therapy, to prevent exacerbation of angina pectoris. In addition, hypertension and arrhythmias may develop.

It is not necessary to discontinue Trandate therapy in patients requiring anaesthesia, but the anaesthetist must be informed and the patient should be given intravenous atropine prior to induction. During anaesthesia Trandate may mask the compensatory physiological responses to sudden haemorrhage (tachycardia and vasoconstriction). Close attention must therefore be paid to blood loss and the blood volume maintained. If beta-blockade is interrupted in preparation for surgery, therapy should be discontinued for at least 24 hours. Anaesthetic agents causing myocardial depression (eg. cyclopropane, trichloroethylene) should be avoided. Trandate may enhance the hypotensive effects of halothane.

In patients with peripheral circulatory disorders (Raynaud's disease or syndrome, intermittent claudication), beta-blockers should be used with great caution as aggravation of these disorders may occur.

Beta-blockers may induce bradycardia. If the pulse rate decreases to less than 50-55 beats per minute at rest and the patient experiences symptoms related to the bradycardia, the dosage should be reduced.

Beta-blockers, even those with apparent cardioselectivity, should not be used in patients with asthma or a history of obstructive airways disease unless no alternative treatment is available. In such cases the risk of inducing bronchospasm should be appreciated and appropriate precautions taken. If bronchospasm should occur after the use of Trandate it can be treated with a beta₂-agonist by inhalation, e.g. salbutamol (the dose of which may need to be greater than the usual in asthma) and, if necessary, intravenous atropine 1mg

Due to a negative effect on conduction time, beta-blockers should only be given with caution to patients with first degree heart block. Patients with liver or kidney insufficiency may need a lower dosage, depending on the pharmacokinetic profile of the compound. The elderly should be treated with caution, starting with a lower dosage but tolerance is usually good in the elderly.

Patients with a history of psoriasis should take beta-blockers only after careful consideration.

Risk of anaphylactic reaction: While taking beta-blockers, patients with a history of severe anaphylactic reaction to a variety of allergens may be more reactive to repeated challenge, either accidental, diagnostic or therapeutic. Such patients may be unresponsive to the usual doses of epinephrine use to treat allergic reaction.

The label will state “Do not take Trandate if you have a history of wheezing or asthma as it can make your breathing worse.”

Concomitant use not recommended:

• Calcium antagonists such as verapamil and to a lesser extent diltiazem have a negative influence on contractility and atrio-ventricular conduction.

• Digitalis glycosides used in association with beta-blockers may increase atrio-ventricular conduction time.

• Clonidine: Beta-blockers increase the risk of rebound hypertension. When clonidine is used in conjunction with non-selective beta-blockers, such as propranolol, treatment with clonidine should be continued for some time after treatment with the beta-blocker has been discontinued..

• Monoamineoxidase inhibitors (except MOA-B inhibitors).

Use with caution:

• Class I antiarrhythmic agents (eg. disopyramide, quinidine) and amiodarone may have potentiating effects on atrial conduction time and induce negative inotropic effect.

• Insulin and oral antidiabetic drugs may intensify the blood sugar lowering effect, especially of non-selective beta-blockers. Beta- blockade may prevent the appearance of signs of hypoglycaemia (tachycardia).

• Anaesthetic drugs may cause attenuation of reflex tachycardia and increase the risk of hypotension. Continuation of beta-blockade reduces the risk of arrhythmia during induction and intubation. The anaesthesiologist should be informed when the patient is receiving a beta-blocking agent. Anaesthetic agents causing myocardial depression, such as cyclopropane and trichlorethylene, are best avoided.

• Cimetidine, hydralazine and alcohol may increase the bioavailability of labetalol.

Take into account:

• Calcium antagonists : dihydropyridine derivates such as nifedipine. The risk of hypotension may be increased. In patients with latent cardiac insufficiency, treatment with beta-blockers may lead to cardiac failure.

• Prostaglandin synthetase inhibiting drugs may decrease the hypotensive effect of beta-blockers.

• Sympathicomimetic agents may counteract the effect of beta-adrenergic blocking agents.

• Concomitant use of tricyclic antidepressants, barbiturates, phenothiazines or other antihypertensive agents may increase the blood pressure lowering effect of labetalol. Concomitant use of tricyclic antidepressants may increase the incidence of tremor.

• Labetalol has been shown to reduce the uptake of radioisotopes of metaiodobenzylguanidine (MIBG), and may increase the likelihood of a false negative study. Care should therefore be taken in interpreting results from MIBG scintigraphy. Consideration should be given to withdrawing labetalol for several days at least before MIBG scintigraphy, and substituting other beta or alpha-blocking drugs.

Trandate Injection is usually well tolerated. Excessive postural hypotension may occur if patients are allowed to assume an upright position within three hours of receiving Trandate Injection.

Most side-effects are transient and occur during the first few weeks of treatment with Trandate. They include headache, tiredness, dizziness, depressed mood and lethargy, nasal congestion, sweating, and rarely, ankle oedema. A tingling sensation in the scalp, usually transient, also may occur in a few patients early in treatment. Tremor has been reported in the treatment of hypertension of pregnancy. Acute retention of urine, difficulty in micturition, ejaculatory failure, epigastric pain, nausea and vomiting have been reported.

There have been rare reports of positive anti-nuclear antibodies unassociated with disease, cases of systemic lupus erythematosus, drug fever, toxic myopathy, hypersensitivity (rash, pruritus, angioedema and dyspnoea), reversible lichenoid rash, impaired vision, dry eyes, cramps, raised liver function tests, jaundice (both hepatocellular and cholestatic), hepatitis and hepatic necrosis, bradycardia and heart block.

Other possible side effects of beta-blockers are: heart failure, cold or cyanotic extremities, Raynaud's phenomenon, paraesthesia of the extremities, increase of an existing intermittent claudication, hallucinations, psychoses, confusion, sleep disturbances, nightmares, diarrhoea, bronchospasm (in patients with asthma or a history of asthma), masking of the symptoms of thyrotoxicosis or hypoglycaemia.

Pharma Limited

(POM)

26 May 2009