Digoxin Flashcards
MOA Digoxin
Inhibition of Na+/K+ ATPase pump – highly expressed in cardiac and skeletal muscle
Calcium no longer kicked out of the cell – Build up of calcium in the cell; sarcoplasm release more calcium increasing in contractility.
Digoxin First-pass Aborption
Passive, non-saturable process
Food has minimal effect
No significant first-pass effect
GI metabolism due to hydrolysis or reduction (~10% population) – decrease F
Absorption interactions DIgoxin
Digoxin Compartment
Described by 2-compartment kinetics
Distribution Phase Digoxin
Distribution phase lasts 6 – 8 h
Obese: IBW
Tissue Distribution Digoxin
Skeletal and cardiac muscle:
Significant due to high levels of N+/K+ ATPase
Adipose:
Vd not influenced by obesity
Factors affecting Digoxin Vd
Digoxin Elimination: Main
Digoxin Toixicty
Digoxin Response Effected by…. (PD)
Factors influencing digoxin Cls
Drug Interactions DIgoxin and SOlution
Drug Interactions with Cls
Analysis of Digoxin
What are DLIS? When is it dtected>
Digoxin-Like Immunoreactive Substances (DLIS)
Not well understood
Endogenous substances
- Phospholipids, steroids, bile acids
Digoxin-free patients with detectable levels:
Renal failure, hepatic failure, low renin hypertension, pregnant women (3rd trimester), neonates, infants
Problems with Digoxin PK Monitoring
Pediatric Dosing Digoxin
Digoxin Dosing Flow Chart
First part of digoxin dosing
When is a loading dose for digoxin given?
Usually not necessary to load in CHF (chronic – do not treat acutely)
Load for atrial fibrillation patients
Use IBW (limited fat distribution) if obese
How is a loading dose given with digoxin?
Cls of Digoxin
Systemic Clearance (ClS) Calculation
Digoxin ClS changes in proportion to ClCr
Estimate of digoxin ClS based upon an empirical linear relationship with ClCr
When is digoxin steady state?
Css,min occurs after 3-5 half-lifes
Long t1/2 - steady state in 5-7 days
Css,min taken 1 hour prior to next dose
When to get anothe rblood sample?
No further sampling if renal function OK and desired clinical effect achieved
Unstable patients: repeat every 5-7 days, OR as dictated by clinical state
Indications for Monitorin g (Full List)
Digoxin Monitoring Other factors
When is digoxin withheld?
Antidotes Digoxin
Indications for DIgoxin Antidote
Digibind Dosing
ANtidote Monitoring
Allergic reactions may occur including anaphylactic shock. Therefore monitor:
