INDICATIONS     CONTRA-INDICATIONS     DOSAGE     SIDE-EFFECTS     PREGNANCY     OVERDOSE     IDENTIFICATION     PATIENT INFORMATION

Logo NORPACE® RETARD Tablets
SCHEDULING STATUS:
S4

PROPRIETARY NAME
(and dosage form):

NORPACE® RETARD Tablets

COMPOSITION:
Each tablet contains disopyramide phosphate 193,2 mg, equivalent to 150 mg disopyramide base in a sustained release matrix.

PHARMACOLOGICAL CLASSIFICATION:
A 6.2 Cardiac depressants

PHARMACOLOGICAL ACTION:
NORPACE is an antiarrhythmic agent which shortens sinus node recovery time, lengthens the effective refractory period of the atrium and has minimal effect on the effective refractory period of the A-V node. The conduction times through the A-V node and the His-Purkinje system are relatively unaffected by NORPACE in the human. However, prolongation of A-V conduction time and conduction time in the His-Purkinje system has been observed in the dog. Also studies on the transmembrane potential of isolated dog Purkinje tissue have shown that there is a decrease in upstroke velocity and an increase in duration of the action potential, identifying NORPACE as a Type 1 antiarrhythmic agent.

INDICATIONS:
NORPACE is indicated for the treatment of patients with various atrial and ventricular arrhythmias. It has been shown to be effective in the control of unifocal and multifocal premature ventricular contractions, premature atrial contractions, paroxysmal atrial tachycardia and paroxysmal ventricular tachycardia when such arrhythmias appear singly or in combination.
NORPACE has been shown to be equally effective in treatment of primary cardiac arrhythmia’s and those which occur in association with a previous myocardial infarction. NORPACE may be used in patients receiving digitalis when adequate control of congestive heart failure has been achieved.

CONTRA-INDICATIONS:
NORPACE is contra-indicated in the pre-existing A-V heart block, shock, glaucoma, urinary retention and hypersensitivity to the drug. NORPACE should not be administered to patients with cardiomyopathy and associated congestive heart failure unless the patient is digitalised and adequately compensated. NORPACE should not be administered to any patient with poorly compensated congestive heart failure.

WARNINGS:
NORPACE should be used with caution in patients with benign prostatic hypertrophy due to its anticholinergic action. Several instances of disopyramide phosphate induced ventricular flutter of the Torsade de Pointes variety have been reported in the literature. Such dysrhythmias are preceded by a prolonged QT interval and seem to occur more frequently in patients receiving higher than normal doses, or in patients with hypokalaemia or hypomagnesaemia. If first degree heart block develops in a patient receiving NORPACE the dosage should be reduced. If the block persists despite the reduction of dosage, continuation of the drug must depend upon an assessment of risk versus benefit. The development of second or third degree heart block requires the discontinuation of NORPACE therapy, unless the heart block is adequately controlled by a temporary or implanted ventricular pacemaker.
In patients with impaired renal function, the therapeutic dose of NORPACE should be reduced and the electrocardiogram should be carefully monitored for lengthening of the P-R, QT and QRS intervals. NORPACE should be used with caution in the presence of digitalis intoxication.
Development of acute urinary retention, for any reason, requires the discontinuation of NORPACE.
NORPACE should not be used together with other medicines with an anticholinergic action e.g. tricyclic antidepressants.
Antiarrhythmic agents may be ineffective in patients with severe hypokalaemia. In such patients the potassium deficiency should be corrected before instituting the NORPACE therapy.

DOSAGE AND DIRECTIONS FOR USE:
For maintenance therapy, the formulation of NORPACE RETARD provides controlled release of the active ingredient so that adequate therapeutic blood levels of NORPACE are maintained over 12 hours’ therapy providing a twice daily dosing schedule. Patients requiring rapid therapeutic response should be initiated on standard capsules.
The usual adult daily maintenance dosage is 2 tablets in the morning and in the evening. Dosage should be individualised on the basis of response and tolerance.
For patients with cardiomyopathy, possible cardiac decompensation and patients with renal insufficiency where creatinine clearance is less than 40 mL/minute the appropriate dosage on NORPACE capsules should be used.
NORPACE RETARD tablets should not be broken or chewed but should be swallowed whole with water.
NORPACE RETARD should not be used for children, nor for patients whose body weight is less than 50 kg.

SIDE-EFFECTS AND SPECIAL PRECAUTIONS:
Anticholinergic effects may be experienced by some patients and will usually be manifested by dry mouth, constipation, blurring of vision, dizziness or difficulty in initiating a urinary stream. These effects are usually mild and transient in nature and may be eliminated by a reduction of dosage.
Other reactions, which have been reported in association with the administration of NORPACE, include nausea, diarrhoea, abdominal pain or cramping, insomnia, syncope, tinnitus and maculopapular or erythematous cutaneous eruptions.
Animal teratology and reproduction studies with NORPACE have demonstrated no adverse effects. However, safe conditions for the use of NORPACE in pregnant women have not been established. The use of any drug in women of childbearing capability requires that the potential benefits of the drug be weighed against its possible hazards to the mother and foetus.
Clinical studies with NORPACE have not been carried out in children, nor have controlled studies been conducted in which NORPACE is used in combination with other antiarrhythmic agents.

KNOWN SYMPTOMS OF OVERDOSAGE AND PARTICULARS OF ITS TREATMENT:
Overdosage may be manifested by anticholinergic effects, dry mouth, blurred vision, urinary hesitancy or retention and significant widening of the QRS complex. The physician should also be aware of the possibility of ventricular fibrillation or cardiac arrest occurring.
Treatment of overdosage is along conventional lines. Assisted respiration may be necessary, as may the use of a cardiac ventricular pacemaker.
It is advisable to administer intravenous infusions of sodium lactate (1,86% isotonic) 250 mL in 10 to 30 minutes, repeated if needed. Ensure normal serum potassium.

IDENTIFICATION:
White, circular, biconvex, film-coated tablet, engraved “SEARLE 954”on one side, plain on the reverse side.

PRESENTATION:
NORPACE RETARD is supplied in blisters containing 100 tablets.

STORAGE INSTRUCTIONS:
Store in a dry place below 30°C.
KEEP OUT OF REACH OF CHILDREN.

REGISTRATION NUMBER:
N/6.2/97

NAME AND BUSINESS ADDRESS OF THE APPLICANT:
Pharmacia South Africa (Pty) Limited
Alphen West G
George Street
Midrand
1685

DATE OF PUBLICATION OF THIS PACKAGE INSERT:
9 April 1985

New addition to this site: February 2005
Source: Pharmaceutical Industry

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