Inotropic Agents in CHF Flashcards
What does digoxin do?
blocks Na/K+ ATPase
How does digoxin affect inotropy
1) block Na/K+ ATPase
2) accumulate Na+ inside cell
3) Na+ exchanged for Ca2+ entry
4) Ca2+ stored in SR
5) incr # of crossbridge btwn actin/myosin
6) incr force of contraction –> inotropy
how does digoxin affect sympathetic NS?
baroreceptors lose sensitivity with digoxin
digoxin incr parasympathetic NS, incr SA and AV node
decr HR
Hemodynamic effects of Digoxin
incr CO
Decr WEdge pressure (from lungs to LA)
incr LV ejection fraction
Neurohormonal effects of Digoxin
1) parasympathetic incr
2) incr baroreceptor sensitivity –> parasymp
3) decr NE
4) decr RAAS
Electro effects of Digoxin
1) slow SA and AV node
How is Digoxin excreted
renally = 70%
Bioavailability of Digoxin at various forms
a) oral
b) IV
a) oral = 75%
b) IV = 100%
metabolism of Digoxin
blocks P-glycoprotein (normally pumps drug out)
accumulate digoxin
Time to peak steady state of digoxin
7-10 days
(half-life = 38 hrs) * 4-5
what is therapeutic serum concentration of digoxin
between 0.5 -1 ng/mL
which drugs have DDI with digoxin due to inhib P-glycoprotein
Quinidine Verapamil Amodarone Dronedarone Propafenone Itraconazole Erythromycin Clarithromycin
What three electrolyte abnormalities cause digoxin toxicity?
1) hypokalemia - incr dig binding
2) hypercalcemia - incr Ca2+ abs into myocytes, incr inotropy
3) hypomagnesemia - cause arrhythmias
Symptoms of Digoxin TOXICITY
1) N/V/ABD PAIN
2) CONFUSION
3) HYPERKALEMIA
4) BRADYKARDIA/ARRHYTHMIA
5) visual effect
Digoxin immune fab mechanism
binds Digoxin and doesn’t allow Digoxin to bind receptor
–> toxicity (arrhythmia, bradycardia, heart block)
