Cardiac Glycosides Flashcards
Give an example of a cardiac glycoside
Digoxin
What is the mechanism of action of digoxin?
Inhibits the Na/K/ATPase membrane pump, which causes an increase in intracellular Na, which is exchanged with extracellular Ca. Intarcellular Ca increases, resulting in an increase in force of myocardial contraction and reduction in conductivity in the AV node.
What are the routes of delivery of digoxin?
- PO
- IV
What must be remembered when giving digoxin IV?
Must be slow
What may need to be done when switching from IV to oral route?
Dose may need to be increased by 20-33% to maintain same effect
What are the indications for digoxin?
- Heart failure
- Atrial fibrillation
What are the contraindications to digoxin?
(in terms of conditions)
- Heart block
- WPW syndrome
- Ventricular tachycardia
- Ventricular fibrillation
- Myocarditis
- Cardiomyopathy
What are the cautions for digoxin?
(in terms of medical state)
- Hypoxia
- Hypokalaemia
- Hypomagnesaemia
- Hypercalcaemia
What drugs increase the risk of digoxin toxicity if given with digoxin?
- Loop and thiazide diuretics
- Spirinolactone
- Calcium channel blockers
- Amiodarone
- Quinine
What monitoring is required with digoxin?
- Plasma digoxin level
- U&Es and GFR
- HR
When should plasma digoxin level be taken?
6 hours post dose, unless toxicity is suspected, in which case as soon as toxicity is suspected
What is the target plasma digoxin level?
1-2 micrograms/L
Why is it important to measure U&Es and GFR with digoxin?
- Patients with renal failure require a lower dose of digoxin
- Electrolyte disturbances may increase toxicity risk
Why is it important to measure HR with digoxin?
HR must remain above 60bpm on maintenance dose
What are the common side effects of digoxin?
- GI disturbance
- Dizziness
- Nausea
- Vomiting
- Blurred or yellowed vision
- Rash
