Inotropic Agents - Dr. Stevens Flashcards
Which is more hydrophobic, digoxin or digitoxin? Why?
Digitoxin is more hydrophobic because it is missing the 12-OH group that digoxin has. It is the most lipophilic cardiac glycoside.
Which has the longer half-life, digoxin or digitoxin? How do the metabolisms compare?
Digitoxin has the longer half-life. It is extensively metabolized by the liver. Digoxin is eliminated 80% unchanged, and is metabolized by the liver as well.
How does quinidine interact with digoxin? (How does blocks P-gp in the renal tube affect digoxin?)
It increases plasma levels of digoxin.
How does verapamil interact with digoxin? (How does inhibiting P-gp efflux of digoxin affect digoxin?)
Digoxin absorption is increased.
How does rifampin affect digoxin? (How does inducing P-gp efflux affect digoxin?)
The absorption of digoxin is decreased.
How does bile acid binding resins affect digoxin? (cholestyramine?)
Less digoxin absorption.
How does furosemide interact with digoxin?
It decreased extracellular K, which makes it more difficult for the Na/K ATPase to pump K back into the cell to reset the chemical gradient. This increases phosphorylation of the ATPase, which allows digoxin to have a higher binding affinity to the extracellular site. This makes the drug work more effectively.
What are some common side effects of cardiac glycosides?
Blurred vision, loss of appetite. Can also be pro-arrhythmic.
What does GI side effects of digoxin often indicate?
Digitalis toxicity
What can you treat digitalis toxicity with?
Digifab, or Digibind. This will help prevent cardiac arrest.
How do phosphodiesterase inhibitors work?
Block degradation of cAMP to AMP
Should PDE3 inhibitors be used for treating acute or chronic CHF?
Acute CHF. Chronic use increases the mortality rate.
What type of medication is Levosimendan? When is it used?
A Ca-sensitizing agent. It is used in acute CHF patients with no risk of arrhythmias.
How does levosimendan work?
It increases contractility by binding the N-terminus of troponin C and stabilizing the Ca-bound conformation. It also activates ATP-regulated K channels and causes vasodilation in smooth muscles.
What B-adrenergic agent is used as an inotropic agent?
Dobutamine.
