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44 Cards in this Set

  • Front
  • Back
what is the term for any of the steroid and steroid glycoside compounds that exert typical positive inotropic and electrophysiologic effects on the heart
digitalis
what is the primary agent used clinically
digoxin
during what condition are the digitalis glycosides used to enhance cardiac output
congestive heart failure

have no effect on cardiac output in normal patient
these drugs are used to treat what type of arrhythmias even if toxic doses may cause cardiac arrhythmias
supraventricular arrhythmias
Where do digitalis compounds come from and what is their common structure
foxglove plant

steroid nucleus with a lactone ring at position 17
what has higher oral availability, digoxin or digitoxin
digitoxin - 90-100%, compared to 70-80%
what has higher oral absorption of digoxin- an encapsulated gel or a tablet
encapsulated gel
name three things that retard absorption
food
antacids
steroid binding resins
there is a close correlation between ___ ___ and plasma digoxin concentration
creatinine clearance
what is the consequence of the 10% of patients who metabolize digoxin to inactive products in the gut lumen by bacteria
higher doses are needed
what is a loading dose of digoxin called
digitalizing dose
name three ways drugs interact with digoxin
1. inhibit absorption (cholestyramine)
2. antibiotics eradicate gut bacteria causing increased plasma concentrations
3. increase digoxin blood levels (antiarrhythmic agents like quinidine, verapamil)
what is meant by positive inotropic action
increased force and velocity of contraction by direct action on the heart, not mediated by catecholamines or by activation of adenylyl cyclase
digitalis binds to the external portion of and inhibits which enzyme
membrane bound Na-K-ATPase
is digitalis binding to Na-K-ATPase enhanced or inhibited by hypokalemia
enhanced
What is the net effect of inhibition of the Na-K-ATPase enzyme
increase in availability of Ca to myocardial contractile proteins
digoxin increases the __ and __ of myocardial contraction by increasing intracellular __
force
velocity
Ca
how does digoxin help CHF
direct positive inotropic action -> inc CO -> increased ejection fraction -> decreases cardiac filling pressure -> reflex reduction in heart rate and peripheral resistance
digoxin causes improved renal perfusion, what does this result in
inhanced sodium excretion and reduction in edema
digoxin reduces venous pressure and left ventricular end diastolic volume, what does this allow?
the distended heart to return to a smaller, more normal size, and relieves edema
What is meant by "digitalis increases the efficency of the failing heart"
CO and O2 consumption
why does the hemodynamic outcome of digitalis administration differ between patients with CHF and those without CHF
the DIRECT VASOCONSTRICTOR ACTION of digitalis
What does digitalis do in patients without CHF
it increases peripheral resistance and therefore afterload; no increased CO because of the increased afterload
Why doesn't digitalis increase afterload in patients with CHF
because the peripheral resistance is already very high due to compensatory vasoconstriction
___ is a complex of signs and symptoms which comprise a recognizable clinical syndrome of pulmonary and peripheral tissue congestion with or without the effects of decreased cardiac output at rest
CHF
digoxin is used to treat CHF resulting from ___, which generally results from MI, myocarditis, toxins, or chronic mechanical overload
left ventricular systolic dysfunction (dilated cardiomyopathy)
does digoxin reduce the overall mortality of HF? does it reduce the rate of hospitalization?
no
yes
how does digoxin act as an anti-arrhythmic action
enhances vagal tone- due to sensitized arterial baroreceptors, increased efferent vagal fiber excitability and increased sensitivity of heart to ACh

slows AV nodal conduction and sinus rate
Name three anti-arrhythmic uses of digoxin
a-fib
a-flutter
Paroxysmal supraventricular tachycardia (PSVT)
what is the most frequent antiarrhythmic use of digoxin
atrial fibrillation
can digoxin achieve and maintain sinus rhythm during a-fib?
no- other antiarrhythmic drugs or DC cardioversion are often needed
name 8 predisposing factors for digtalis toxicity
1. ionic imbalance
2. DECREASED K
3. increased Ca
4. heart disease
5. RENAL DYSFUNCTION - DIGOXIN
6. LIVER DYSFUNCTION- DIGITALIS
7. hypothyroidism
8. drug interactions
name four manifestations of digitalis toxicity
1. arrhythmias
2. stimulate "trigger zone"- anorexia, nausea, vomitting
3. visual changes
4. neurologic changes: HA, fatigue, insomnia, confusion, depression
What particular arrhythmia is specific to digoxin toxicity?
none- it can cause most any type of arrhythmia or conduction block
what nerves to the heart are effected by digoxin
both sympathetic and parasympathetic nerves are activated
at toxic doses, the direct toxic effect of digoxin on the ventricle, combined with the enhanced sympathetic input to the ventricle can cause
synergy- AV dissociation, premature ventricular beats, v-tach, and fibrillation
name five steps to treat digoxin toxicity
1. stop digoxin and monitor cardiac rhythm
2. correct electrolytes
3. KCl- unless AV block present
4. atropine or pacing for bradyarrhythmias
5. digoxin-immune Fab or lidocaine for ventricular arrhythmias
except for ___, oral agents for chronic positive inotropic therapy have been show to increase mortality due to increased arrhythmias
digoxin
name two sympathomimetic amines parenterally administered primarily in cardiogenic shock, low output states which follow open heart surgery, and severe refractory CHF
dopamine- i.v.
dobutamine- i.v.
name two phophodiesterase inhibitors whose inotropic action is due to inhibition of cyclic nucleotide phophodiseterase isoenzyme III which leads to inc intracellular calcium
inamrinone
milrinone
what else do inamrinone and milrinone do
vasodilators
how are inamrinone and milrinone given
parenterally
toxicity of which, inamrinone or milrinone, includes reversible thrombocytopenia
inamrinone
which, inamrinone or milrinone, is the agent of choice for short term i.v therapy for severe CHF
milrinone