Digoxin Flashcards
What is digitalis?
It is the term used for the genus name of the family of plants in
which cardiac glycosides occur naturally.
Katzung BG, Masters, SB, & Trevor AJ. Basic and Clinical
Pharmacology. 12th ed. New York: McGraw-Hill; 2012: 215.
Describe the impact digoxin has on resting
membrane potentials of cardiac cells.
Digoxin decreases the resting membrane potentials of cardiac
cells through the inhibition of the sodium pump. The sodium
pump is vital in the maintenance of normal gradients of
potassium and sodium ions. This inhibition decreases the
resting membrane potential, which in turn increases the
excitability (automaticity) of the cardiac cells by altering the
potassium ion gradient.
Stoelting RK, Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. Philadelphia, PA: Lippincott Williams and
Wilkins; 2006: 312.
What is the prototypical cardiac glycoside?
Digoxin
Katzung BG, Masters, SB, & Trevor AJ. Basic and Clinical
Pharmacology. 12th ed. New York: McGraw-Hill; 2012: 216.
How does digoxin affect cardiac contractility?
Digoxin increases cardiac contractility.
Guyton AC, & Hall, JE. Textbook of Medical Physiology. 12th
ed. Philadelphia: Saunders; 2011: 214.
How does digoxin increase cardiac contractility?
Through the increase of intracellular concentrations of calcium
ions in cardiac cells. Inhibition of the sodium pump increases
the concentration of intracellular sodium. This increased
concentration of sodium causes a reduction in the extrusion of
calcium ions from the sodium pump.
Katzung BG, Masters, SB, & Trevor AJ. Basic and Clinical
Pharmacology. 12th ed. New York: McGraw-Hill; 2012: 216.
How does digoxin affect the sodium-potassium
adenosine triphosphatase ion transport system (also
known as the sodium pump)?
It reversibly and selectively inhibits the sodium pump.
Stoelting RK, Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. Philadelphia, PA: Lippincott Williams and
Wilkins; 2006: 312.
How does digoxin affect the conduction velocity
through the AV node at therapeutic dosages?
It reduces it.
Katzung BG, Masters, SB, & Trevor AJ. Basic and Clinical
Pharmacology. 12th ed. New York: McGraw-Hill; 2012: 217.
Is digoxin metabolized to a great extent in humans?
No. A large amount of digoxin (almost two thirds) is excreted by
the kidneys unchanged.
Katzung BG, Masters, SB, & Trevor AJ. Basic and Clinical
Pharmacology. 12th ed. New York: McGraw-Hill; 2012: 216.
Plasma clearance of digoxin is primarily dependent
upon what organ?
The kidneys
Stoelting RK, Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. Philadelphia, PA: Lippincott Williams and
Wilkins; 2006: 313.
How does creatinine clearance affect renal
clearance of digoxin?
Renal clearance of digoxin is proportional to creatinine
clearance. Therefore, the elimination half-time is reduced in
proportion to the reduction in creatinine clearance in the
presence of renal dysfunction.
Stoelting RK, Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. Philadelphia, PA: Lippincott Williams and
Wilkins; 2006: 214.
Katzung BG, Masters, SB, & Trevor AJ. Basic and Clinical
Pharmacology. 12th ed. New York: McGraw-Hill; 2012: 216.
Does digoxin affect the autonomic nervous system?
Are these effects more predominant in the
sympathetic or parasympathetic nervous system?
Yes, digoxin affects the autonomic nervous system. These
effects are more prevalent in the parasympathetic nervous
system. Effects are manifested as a reduction in heart rate
caused by decreased activity of the SA node and prolongation
of the effective refractory period.
Stoelting RK, Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. Philadelphia, PA: Lippincott Williams and
Wilkins; 2006: 313.
Describe how digoxin causes toxicity in the GI tract.
Digoxin causes toxicity in the GI tract through direct effects and
by stimulation of the central nervous system, specifically vagal
stimulation and chemoreceptor trigger zone stimulation.
Katzung BG, Masters, SB, & Trevor AJ. Basic and Clinical
Pharmacology. 12th ed. New York: McGraw-Hill; 2012: 217.
- Outside the heart, where does digitalis toxicity
most frequently manifest? 2. List the symptoms
associated with this toxicity.
- The GI tract. 2. Nausea, diarrhea, vomiting, anorexia.
Katzung BG, Masters, SB, & Trevor AJ. Basic and Clinical
Pharmacology. 12th ed. New York: McGraw-Hill; 2012: 217.
List the most common cardiac signs of digitalis
toxicity.
Bigeminal rhythm, second degree AV block, AV junctional
rhythm, and premature ventricular depolarizations.
Katzung BG, Masters, SB, & Trevor AJ. Basic and Clinical
Pharmacology. 12th ed. New York: McGraw-Hill; 2012: 217.
How does quinidine affect plasma levels of digoxin?
Quinidine increases plasma levels of digoxin in a dosedependent
manner.
Stoelting RK, Hillier SC. Pharmacology and Physiology in
Anesthetic Practice. Philadelphia, PA: Lippincott Williams and
Wilkins; 2006: 316.
