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27 Cards in this Set
- Front
- Back
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What are the 2 main therapeutic uses for digitalis glycosides?
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Congestive heart failure
Supraventricular arrhythmias |
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What is the very general strategy to improve contractility pharmacologically?
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Increase intracellular Ca
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What is the MOA for digoxin?
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Inhibits the Na K ATPase, which normally repolarizes after the Na influx. With increased Na in the cell, it impacts the Na Ca exchanger, resulting in more Ca coming in the cell.
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What are the 'additional' effects of digoxin?
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Neurohumoral:
Improved baroreceptor function, decreased sympathetic activity, decreased vascular resistance, decreased CVP Reduction in circulating hormones Increased parasympathetic tone |
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What are the direct electrophysiologic effects of digitalis?
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Inhibition affects membrane potential
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What are the indirect electrophysiologic effects of digitalis?
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Enhanced vagal tone (due to sensitized arterial baroreceptors, increased sensitivity in heart to ACh)
Reduced sympathetic activity initially, at toxic concentrations get increased sympathetic activity Predominant in SA and AV nodes and atrial tissue |
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How long does it take digoxin to reach steady state concentrations?
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About 1 week
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Why might antibiotics affect digoxin activity?
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About 10% of patients have gut metabolism of digoxin by bacteria
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How is digoxin excreted?
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Renal - proportional to GFR
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What is the digoxin endpoint in treating heart failure?
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Low therapeutic range
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What is special about digoxin's contractility increasing properties?
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Only drug to increase contractility that doesn't increase mortality
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What kind of HTN/CHF is best treated with digitalis?
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Systolic dysfunction, moderate-severe CHF
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What hemodynamic features are found in people who respond better to digoxin?
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Lower cardiac index, higher PCWP
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When is digoxin contraindicated for arrhythmias?
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Atrial fibrillation
WPW syndrome |
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What arrhythmias is digitalis used for?
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A-fib
A-flutter PSVT |
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Why is diltiazem preferred to digitalis for arrhythmias?
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Diltiazem (IV) has a faster onset
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Generally, what are the first line agents for a-fib, a-flutter?
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Ca channel blockers and Beta blockers
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What is the excellent bioassay for myocardial digoxin concentrations?
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Ventricular response
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Why is digitalis used in PVST?
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Converts to normal sinus rhythm by increasing vagal (parasympathetic) tone
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What causes PSVT with AV block?
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Digitalis toxicity
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What is the more effective therapy for PSVT besides digitalis?
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Ca channel blockers
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What are 3 factors that influence individual sensitivity to digitalis?
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Hypokalemia
Concominant drug administration (anesthetics, catecholamines, sympathomimetics) Renal function |
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What is the general theme of digitalis toxicity?
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Neurally mediated
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What causes the arrhythmias of digitalis toxicity?
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DADs, cellular depolarization, and enhanced automaticity
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What are the symptoms of digitalis toxicity?
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Arrhythmias
AV block GI: anorexia, nausea, vomiting Neurological: visual disturbances, headache, confusion |
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What are the most common arrhythmias with digitalis toxicity?
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Arrhythmias relating to ectopic pacemakers with or without AV block
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What are the pharmacologic effects of phosphodiesterase inhibitors?
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Positive inotropic effect
Venous and arterial vasodilator Enhanced AV nodal conduction Can promote ventricular arrhythmias |
