Norbit

Norbit is used in the treatment of cardiac arrhythmias as follows:-

1. The prevention and treatment of arrhythmias occurring after myocardial infarction.

2. Maintenance of normal rhythm following electroconversion eg atrial fibrillation, atrial flutter.

3. Persistent ventricular extrasystoles.

4. Control of arrhythmias following the use of digitalis or similar glycosides.

5. Suppression of arrhythmias during surgical procedures eg cardiac catheterisation.

6. The prevention of paraxysmal supraventricular tachycardia.

7. Other types of arrhythmias e.g. atrial extrasystoles, Wolff-Parkinson-White Syndrome.

Route of administration

Oral

300 mg to 800mg daily in divided doses.

Children :

Not recommended as insufficient data available.

Elderly

A dose reduction due to reduced renal and hepatic function in the elderly (especially elderly non-smokers) should be considered

Disopyramide is contra-indicated in un-paced second or third degree atrioventricular block; bundle-branch block associated with first-degree atrioventricular block ; unpaced bifasicular block; pre-existing long QT syndromes; severe sinus node dysfunction ; severe heart failure, unless of secondary to cardiac arrhythmia ; hypersensitivity to disopyramide. It is also contra-indicated in concomitant administration with other anti-arrhythmics or other drugs liable to provoke ventricular arrythmias, especially Torsade de Pointes. The sustained release formulation is contra-indicated in patients with renal or hepatic impairment.

Some adverse reactions may impair the patients ability to concentrate and react, and hence the ability to drive or operate machinery..

In some cases, severe hypoglycaemia resulted in coma.

Very rarely: cholestatic jaundice, headache, dizzy sensation, neutropenia.

Rapid infusion may cause profuse sweating.

Reporting of suspected adverse reactions

Reporting of suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme at: www.mhra.gov.uk/yellowcard

There is no specific antidote for disopyramide. Prostigmine derivatives can be used to treat anticholinergic effects. Symptomatic supportive measures may include : early gastric lavage ; administration of a cathartic followed by activated charcoal by mouth or stomach tube ; IV administration of isoprenaline, other vasopressors and/or positive inotropic agents ; if needed - infusion of lactate and/or magnesium, electro-systolic assistance, cardioversion, insertion of an intra-aortic balloon for counterpulsion and mechanically assisted ventilation. Haemodialysis, haemofiltration or haemoperfusion with activated charcoal has been employed to lower the serum concentrations of the drug.

Class 1 anti-arrhythmic agent.

It decreases membrane responsiveness, prolongs the effective refractory period (ERP) and slows automaticity in cells with augmented automaticity. Effective refractory period of the atrium is lengthened, ERP of the A-V node is shortened and conduction in accessory pathways is prolonged.

Disopyramide is a myocardial depressant and has anti-cholinergic effects.

Elimination phase of plasma t1/2: 5-8 hours. Increased in hepatic impairment, cardiac and hepatic disease.

Protein binding: 50 - 60%. Saturable and concentration dependent.

Volume of distribution: Variable according to method of determination.

Metabolism: Approximately 25% of a dose metabolised to a mono-N-dealkylated derivative. Additional 10% as other metabolites.

Excretion: 75% unchanged drug via urine, remainder in faeces mono-N-dealkylated metabolite 25% in urine, 64% via faeces.

Not applicable.

Not known.

None.