Digoxin Flashcards
MoA
Cardiac glycose. Increases force of myocardial contraction and reduced conductivity within AV node
What is the therapeutic range for serum digoxin concentration
0.7-2.0 nanograms/ml
Major routes of elimination
Renal excretion
Hepatic metabolism to active metabolites
Dose of digoxin to prescribe
Loading dose of 250mcg-750mcg daily for 7 days, followed by maintenance dose
When is the clinical response usually seen by
Within 1 week
Dose of digoxin to prescribe for elderly and renal impairment
Seek specialist advice for elderly and renal impairment - loading dose of digoxin will need to be reduced
Usual maintenance dose
125mcg-250mcg daily - adjust according to renal function, initial loading dose, and heart rate response
Dose to prescribe if a rapid response is needed
- More rapid response may be achieved by prescribing 750mcg-1500mcg in divided dose over 24 hours
- However, Previous expert reviews suggest usually no more than 1000mcg (1mg) needed in 25 hours
- If more rapid clinical response is required, consider referral to secondary care
If you take digoxin with some medications, it requires a dose adjustment. What are the medications and what is the dose change required?
Concurrent use of amiodarone, dronedarone and quinine: reduce dose of digoxin by half
When may dose reductions of digoxin be required
- If digoxin (or another cardiac glycose) has been given in the preceding 2 weeks
- Concurrent use of amiodarone, dronedarone, quinine: halve dose of digoxin
Switching from IV to oral digoxin
May need to increase dose by 20-33% to maintain the same plasma-digoxin concentration
Contraindications
- Constrictive pericarditis (unless to control AF or improve systolic dysfunction, but use with caution)
- Hypertrophic cardiomyopathy (unless concomitant AF and heart failure, but use with caution)
- Intermittent complete heart block
- Myocarditis
- Second degree AV block
- Supra ventricular arrhythmias associated with accessory conducting pathways e.g. Wolff-Parkinson-White syndrome (although can be used in infancy)
- Ventricular tachycardia or fibrillation
Cautions
- Hypercalcaemia - risk of digitalis toxicity
- Hypokalaemia - risk of digitalis toxicity
- Hypomagnesaemia - risk of digitalis toxicity
- Hypoxia - risk of digitalis toxicity
- Recent MI
- Severe respiratory disease
- Sick sinus syndrome
- Thyroid disease
- Elderly - prescription potentially inappropriate (STOPP criteria)
○ In heart failure with normal systolic ventricular function (no clear evidence of benefit)
○At long term dose greater than 125mcy daily if eGFR less than 30ml/min/1.73m2 (risk of digoxin toxicity if plasma levels not measured) In heart failure with normal systolic ventricular function (no clear evidence of benefit)
At long term dose greater than 125mcy daily if eGFR less than 30ml/min/1.73m2 (risk of digoxin toxicity if plasma levels not measured)
Use in pregnancy
May need dose adjustment
Use in breastfeeding
Amount too small to be harmful