Digoxin Flashcards
What 3 formulations can be used for digoxin?
IV
PO
Elixir
IV digoxin is absorbed by how much percent?
100%
PO digoxin is absorbed by how much percent?
70%
Elixir digoxin is absorbed by how much percent?
80%
How is PO digoxin converted to IV?
Decrease PO dose by 25%
How is IV digoxin converted to PO?
Increase IV dose by 25%
In what location is digoxin mainly absorbed?
Small intestine
What 3 things can decrease the absorption for digoxin?
- High fiber meals
- Binding drugs
- Malabsorption syndromes
What can increase the absorption for digoxin?
- P-gp inhibitors (amiodarone, verapamil, and quinidine)
Where is digoxin mainly distributed?
Lean organ tissue - muscle, heart, kidneys, and liver
What should the volume of distribution (Vd) be in digoxin?
7 L/kg
Is Vd affected by obese patients?
NO
What two things can decrease the Vd?
- Renal failure
- Hyperkalemia
What major site is digoxin metabolized?
GI tract-hydrolysis (stomach acid) & liver metabolism
What is the name of the bacteria that inactivates digoxin?
Eubacterium lentum
What two classes of drugs eradicates E. lentum causing digoxin to increase?
Macrolide antibiotics
Tetracycline antibiotics
How is digoxin excreted/eliminated?
75% kidneys
25% biliary/hepatic elimination
What is the half-life of digoxin?
36 hours
What health conditions or drugs decrease the clearance of digoxin?
- Heart failure (HF)
- Hypothyroid
- Hypokalemia
- Amiodarone
- Verapamil
What health conditions or drugs increase the clearance of digoxin?
- Hyperthyroid
- Digibind
What is the loading dose (LD) of digoxin PO?
1 to 1.5 mg PO
What is the LD of digoxin IV?
0.5 to 1 mg IV
How is the LD of digoxin administered? (HINT = step by step process)
- 50% of dose initially
- 25% of dose at 6 hours
- 25% of dose at 12 hours
What is the maintenance dose (MD) of digoxin?
0.125 to 0.5 mg daily
What weight (IBW, Adj. BW, Act. BW) should be used to calculate the dose of digoxin?
IBW
If digoxin is being used for HF, what should the therapeutic range be?
0.5 to 1.0 mcg/L
If digoxin is being used for AF, what should the therapeutic range be?
0.8 to 2.0 mcg/L
When should digoxin therapeutic levels be checked after LD has been administered?
Within 12-24 hours
(T/F) - Checking the levels of digoxin within 12-24 hours after LD has been administered helps to determine the MDs
FALSE - ensures us the patient isn’t toxic
When should digoxin therapeutic levels be checked if no LD is given?
wait 3-5 days before obtaining serum levels
If IV MD digoxin is given, when should levels be checked?
After 6 hours from administration
If PO MD digoxin is given, what should be done?
Trough concentrations should be ordered
When would digoxin toxicities most likely occur? [HINT = at what concentration]
> 2.0 mcg/L
What are some common cardiac toxicities associated with digoxin?
- Proarrhythmic
- Bradycardia
- Atrial tachycardia w/ AV block
- Fatal ventricular arrhythmias
What are some common GI toxicities associated with digoxin?
- Nausea
- Vomiting
- Diarrhea
- Abdominal pain
What are some common CNS toxicities associated with digoxin?
- Headache
- Fatigue
- Vertigo
- Confusion
What are some common visual disturbances associated with digoxin?
- Blurriness
- Yellow-green halo vision
Can potassium affect digoxin levels or toxicities?
Yes - hypokalemia increases digoxin potency
Can magnesium affect digoxin levels or toxicities?
Yes - hypomagnesemia increases digoxin toxicity (arrhythmias)
Can calcium affect digoxin levels or toxicities?
Yes - hypercalcemia increases digoxin toxicity
What medication is an antidote for digoxin?
Digibind (Digoxin immune Fab)
How do you calculate the dose of Digibind?
Calculated as the # of vials
Is the # of Digibind rounded up or down?
Rounded up - always
