PURGOXIN TABLETS 0,25 mg
(and dosage form)
PURGOXIN TABLETS 0,25 mg
Each tablet contains 0,25 mg digoxin.
A 6.3 Cardiac glycosides.
The main property of digoxin is its ability to increase the force of myocardial contraction. The effects of digoxin in patients with heart failure - increased cardiac output, decreased heart size, venous pressure, and blood volume; diuresis and relief of edema - are due to increased contractile force, a positive inotropic action. The second important action of digoxin is to slow the ventricular rate in atrial fibrillation or flutter.
Digoxin exerts direct effects on the heart that modify both its mechanical and electrical activity. It also acts directly on the smooth muscle of the vascular system. In addition digitoxin exerts a number of effects on neural tissue and thus indirectly influences the mechanical and electrical activity of the heart and modifies vascular resistance and capacitance. Finally, changes in the circulation brought about by digoxin often result in reflex alterations in autonomic activity and hormonal balance that indirectly influence cardiovascular function.
After oral administration, the concentration of digoxin in plasma typically reaches a peak in 2 to 3 hours, the maximal effect is apparent in 4 to 6 hours. If a loading dose of digoxin is not given up to 1 week can elapse before steady-state plasma concentrations are attained, since the half-life of digoxin in the body is 1 to 2 days.
Digoxin tablets may be used for initial digitalisation or maintenance therapy whenever digitalis therapy is indicated, such as the treatment of auricular fibrillation and congestive heart failure.
Digoxin is contra-indicated in patients with ventricular fibrillation and hypertrophic obstructive cardiomyopathy unless there is severe cardiac failure.
Digoxin is also contra-indicated in patients with the Wolff-Parkinson-White syndrome, especially if it is accompanied by atrial fibrillation, since digoxin may precipitate ventricular tachycardia or fibrillation.
Injections of calcium salts should not be given during digoxin therapy.
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DOSAGE AND DIRECTIONS FOR USE:
The initial dose for rapid digitalisation is 2 to 3 tablets thereafter 1 - 2 tablets every six hours till the ventricular rate has dropped to normal. A total dose of 4 to 6 tablets given over 24 hours is normally adequate. A suitable maintenance dose should then be ascertained, which is 1 tablet once or twice daily. If a patient was digitilised in the preceeding 10 to 14 days the initial dose should be reduced accordingly.
The dosage should also be carefully controlled in patients with impaired renal function and elderly persons. Higher doses are necessary to provide a chronotropic effect in cardiac arrhythmias.
SIDE-EFFECTS AND SPECIAL PRECAUTIONS:
Digoxin commonly produces side effects because the margin between the therapeutic and toxic doses is small.
Nausea, vomiting, and anorexia may be among the earliest symptoms of large doses of digoxin.
The most serious adverse effects are those on the heart. Toxic doses may cause or aggravate heart failure. Atrial or ventricular arrhythmias and defects of conduction are common and may be an early indication of excessive overdosage. In general the incidence and severity of arrhythmias is related to the severity of the underlying heart disease. Almost any arrhythmia may ensue, but particular note should be made of supraventricular tachycardia, especially atrioventricular (AV) junctional tachycardia and atrial tachycardia with block. Ventricular arrhythmias including extrasystoles, sinoatrial block, sinus bradycardia, and AV block may also occur.
Chronic digoxin toxicity is associated with hypokalaemia and adverse reactions to digoxin may be precipitated if there is potassium depletion such as may be caused by the prolonged administration of diuretics.
Allergic and skin reactions; thrombocytopaenia has been reported.
Digoxin may cause gynaecomastia at therapeutic doses and may have some oestrogenic activity.
Visual disturbances including blurred or misted vision may occur; colour vision may be affected with objects appearing yellow or less frequently green, red, brown, blue or white.
For the treatment of chronic poisoning, temporary withdrawal of digoxin is necessary, with subsequent doses adjusted according to the needs of the patient. Potassium supplements should be given to correct hypokalaemia.
Digoxin should be used with caution in heart block, acute myocarditis such as rheumatic carditis and in patients with advanced heart failure and severe pulmonary disease.
Should be given with caution to patients who have received cardiac glycosides before.
Early signs of digoxin toxicity should be watched for and the heart-rate should generally be maintained above 60 beats/minute.
Digoxin doses should be reduced and plasma-digoxin concentrations monitored in patients with impaired renal function, in the elderly, and in premature infants; they should be carefully controlled in patients with electrolyte imbalance, or thyroid dysfunction.
The effects of digoxin are enhanced by hypokalaemia, hypomagnesia, hypercalcaemia, hypoxia and hypothyroidism and doses may need to be reduced until these conditions are corrected.
Drugs which cause electrolyte disturbances increase the risk of toxicity from digoxin. Thiazides and loop diuretics cause potassium depletion and also hypomagnesaemia which may lead to cardiac arrhythmias Corticosteroids, carbenoxolone and amphotericin cause hypokalaemia.
Hypercalcaemia may also increase toxicity, and IV administration of calcium salts is best avoided during digoxin therapy.
Digoxin should be given cautiously to patients receiving parathyroid extract or large doses of Vitamin D. Quinidine reduces renal excretion and thus plasma-digoxin levels may be doubled.
Digoxin plasma concentrations should be monitored if phenytoin, phenobarbitone or rifampicin is administered.
Concurrent administration of verapamil, nifedipine or amiodarone, and digoxin may increase plasma-digoxin concentrations and lead to atrioventricular block in some patients.
Suxamethonium may increase the risk of cardiac arrhythmias, and bradycardia may be anticipated in patients given beta-blockers with digoxin.
KNOWN SYMPTOMS OF OVERDOSAGE AND PARTICULARS OF ITS TREATMENT:
Nausea, vomiting and anorexia may be among the earliest symptoms of digoxin overdosage; diarrhoea and abdominal pain may also occur.
Certain neurological effects are also common symptoms of digoxin overdosage and include headache, facial pain, fatigue, weakness, dizziness, drowsiness, disorientation, mental confusion, bad dreams and more rarely delirium, acute psychoses, and hallucinations. Convulsions have also been reported.
Hyperkalaemia occurs in acute overdosage.
Frequent etopic heart beats indicate poisoning of the myocardium and atricular or ventricular arrhythmias and defects of conduction may be early indications of overdosage.
In the early stages of acute poisoning, the stomach should be emptied by emesis or aspiration and lavage. Activated charcoal may be given to prevent absorption of digoxin. Anti-arrhythmic treatment may be necessary, particularly if there is a risk of progression to ventricular fibrillation.
Potassium chloride may be given in hypokalaemic patients providing that renal function is normal and heart block is not present.
In massive overdosage progressive hyperkalaemia occurs and is fatal unless reversed. Glucose infusions and injections of soluble insulin have been given. Massive overdosage has been treated successfully with fragments of digoxin-specific antibodies.
White, biconvex bisected tablet.
Securitainers containing 100, 500 and 1000 tablets.
Store below 25°C. Store in airtight containers. Protect from light.
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