Inotropic drugs: limitations in HF Flashcards Preview

CVPR: CV Unit I > Inotropic drugs: limitations in HF > Flashcards

Flashcards in Inotropic drugs: limitations in HF Deck (10):

Categories of positive inotropic agents

-cardiac glycosides
-beta agonists
-phosphodiesterase inhibitors (PDEi)
-calcium sensitizing agents


Major goal/target of positive inotropic agents

increase effective intracellular Ca2+ concentration


Major indications for use of digitalis (2)

-treatment of chronic CHF in the presence of atrial fibrillation
-treatment of chronic CHF when there is confirmed S3 gallop


Digitalis =

-plant source of digitoxin and digoxin


Digitalis MOA

-blocks Na+/K+/ATPase pump (which normally pumps Na+ in and K+ out)
-blockage --> increase [Na+]in
-increased [Na+]in --> Na+/Ca2+ exchanger begins pumping Na+ out and thus bringing Ca2+ in --> increased [Ca2+}in


Negative effects of Digitalis

-- Increase intravascular Ca++ too
– Increase sympathetic tone by activation of CNS descending pathways
– Decrease NE reuptake


Positive effects of Digitalis

-Increase parasympathetic (vagal) tone
– Increase renal blood flow thereby decreasing circulating blood volume
– Positive inotropic effect decreases sympathetic tone by
resolving the symptoms of CHF


Digoxin half-life and route of elimination

-t1/2=1.7 days
-ROE=renal excrete of unchanged drug; limited hepatic metabolism


Digitoxin half-life and route of elimination

-t1/2=7 days
-ROE=hepatic degredation w/renal excretion of metabolites


Problems w/positive inotropic agents (5)

1. Tachyphylaxis (desensitization, tolerance)
2. Substantially increased MVO2
3. Increased risk of sudden death (proarrhythmic)
4. Generally not orally active
5. Very short plasma half-life