Introduction
Plasma concentration alone does not determine whether a patient has developed digoxin toxicity. Toxicity may occur even when the concentration is within the therapeutic range. The BNF advises that the likelihood of toxicity increases progressively from 1.5 to 3 mcg/l.
Aetiology
Precipitating factors
- classically: hypokalaemia
- digoxin normally binds to the ATPase pump on the same site as potassium. Hypokalaemia → digoxin more easily bind to the ATPase pump → increased inhibitory effects
- increasing age
- renal failure
- myocardial ischaemia
- hypomagnesaemia, hypercalcaemia, hypernatraemia, acidosis
- hypoalbuminaemia
- hypothermia
- hypothyroidism
- drugs: amiodarone, quinidine, verapamil, diltiazem, spironolactone (competes for secretion in distal convoluted tubule therefore reduce excretion), ciclosporin. Also drugs which cause hypokalaemia e.g. thiazides and loop diuretics
Clinical features
Features
- generally unwell, lethargy, nausea & vomiting, anorexia, confusion, yellow-green vision
- arrhythmias (e.g. AV block, bradycardia)
- gynaecomastia
Management
Management
- Digibind
- correct arrhythmias
- monitor potassium