Cardiac Glycosides - Digoxin Flashcards
What is the mechanism of action of the drug Digoxin?
Blocks Na/K ATPase leading to intracellular accumulation of Na+. This reduces the calcium exchanger activity leading to Calcium influx and contraction! “Ionotropy”
What are the cardiac effects of Digoxin?
Decrease end diastolic volume and end systolic volume due to increase ionotropy!
Decreases pulmonary and systemic venous pressure.
Causes a reflex decrease in SANS
Increases vagal effect
Increases coronary flow
Decreases renal resistance
What effect does Digoxin have on body nerves?
Direct Vagal effect!
Increases vagal tone decreasing AV conduction.
Increases the PR interval
Decreases the action potential duration.
An increased PR interval with ST depression looking like a hockey stick is indicative of what?
Digoxin side effects!
Digoxin is pro arrhythmic
What is the half life of Digoxin?
36-48 hours in patients with normal renal function.
When is the steady state of digoxin reached
Reached after 7 days of dosing.
How is digoxin normally excreted?
Excreted by the kidney!
What unique tolerance is present in 10% of the population to Digoxin?
Pts with the bacterium Eubacterium lentum have a tolerance.
What drugs interact with digoxin?
Antiarrythmic class Ia and IV
Spironolactone
Vasodilators
Cimetidine
What electrolyte must be monitored in digoxin use?
Potassium! Commonly causes hypokalemia
Can also cause an acid base unbalance.
What is the role of digoxin in the treatment of heart failure?
Used very frequently in the treatment of heart failure. Especially in CHF with AF.
IT DOES NOT IMPROVE ALL-CAUSE MORTALITY.
what are the antidotes for digoxin overdose?
Cholestyramine
Digoxin immune FAB
Causes digoxin excretion in urine.
What type of drug are Inamrinone and milrinone?
These are both phosphodiesterase inhibitors.
What is the MoA of phosphodiesterase inhibitors Inamirone and milrinone?
These drugs both decrease cellular cyclic AMP degradation elevating cAM levels in cardiac and smooth muscle myocytes.
What cardiovascular effects do inamirone and milrinone have?
These both stimulate myocardial contractility
Accelerate myocardial relaxation
Balance arterial and venous diation
Act to increase cardiac output.
