LANOXIN

What it is

LANOXIN contains digoxin. The tablet formulations contain digoxin 250 microgram or digoxin 62.5 microgram. Digoxin is a cardiac glycoside with molecular haemodynamic, neurohumoral and electrophysiological effects. Its primary action is to reversibly inhibit the alpha subunit of sodium-potassium adenosine triphosphatase (ATPase).

Approved indications

— Congestive heart failure. — Atrial fibrillation. — Paroxysmal atrial tachycardia.

Dosing overview

Dosage of digoxin must be adjusted individually for each patient. For adults and children over 10 years with normal renal function, the usual dose is 250 microgram as a single daily dose or, when required, up to 500 microgram daily in divided doses. Elderly patients require smaller doses because impairment of renal function in the elderly is common and the sensitivity of the myocardium to the drug is thought to be increased. A usual dose in the elderly is 125 microgram daily. For infants and children under 10 years, maintenance dosing is 10 to 20 microgram per kilogram bodyweight daily, in single or divided doses, with the lower dose range applying in neonates and when digoxin is administered parenterally.

Key safety warnings

Concurrent use of digoxin with diuretics can predispose patients to toxicity reactions due to electrolyte disturbances caused by diuretics, primarily hypokalaemia but also hypomagnesaemia. Periodic electrolyte determinations must be performed in patients receiving digoxin and a diuretic. Hypokalaemia and hypomagnesaemia increase the risk of digitalis toxicity, and hypokalaemia can result from drugs, dialysis, mechanical suction of gastrointestinal secretions, malnutrition, diarrhoea, prolonged vomiting, old age, and long standing heart failure. Ischaemic heart disease, acute myocardial infarction, acute myocarditis, myxoedema, or severe pulmonary disease are associated with increased sensitivity of the myocardium to the effects of digoxin and increased risk of digitalis-induced arrhythmias. Hypoxia increases risk of toxicity to digoxin. Digoxin has a narrow therapeutic index and adverse reactions are in general dose-dependent and occur at doses higher than those needed to achieve a therapeutic effect. Adverse reactions are less common when digoxin is used within the recommended dosage range or therapeutic serum concentration range.

Contraindications

Digoxin is contraindicated in intermittent complete heart block or second degree atrioventricular block (especially if there is a history of Stokes-Adams attacks), ventricular tachycardia and ventricular fibrillation, and arrhythmias caused by cardiac glycoside intoxication. Digoxin is contraindicated in supraventricular arrhythmias associated with an accessory atrioventricular pathway, as in Wolff-Parkinson-White syndrome, unless the electrophysiological characteristics of the accessory pathway and any possible deleterious effect of digoxin have been evaluated. If an accessory pathway is known or suspected and there is no history of previous supraventricular arrhythmias, digoxin is similarly contraindicated. Digoxin is contraindicated in hypertrophic obstructive cardiomyopathy, unless there is concomitant atrial fibrillation and heart failure, but caution should be exercised even then. Digoxin is contraindicated in hypersensitivity to digoxin, other digitalis glycosides, or any other constituent.

PBS listing

LANOXIN tablet 250 micrograms is listed on the PBS with restriction, at an ex-manufacturer price of A$5.88.

Regulatory history

LANOXIN was first approved on 29 July 2002. Earlier ARTG registrations for the LANOXIN brand (sponsored by Aspen Pharmacare) include multiple formulations first listed from 1991, including adult and infant injections, tablets, and paediatric elixir.