Separate digoxin into DIG - OX - IN. Imagine an ox (OX) digging (DIG) in (IN) its hind legs and refusing to continue pulling a cart. It's decreasing its heart rate since it's not moving, but increasing its contractility since it's digging in its hind legs, as if ready to lunge. The ox is saying K Nah, to signify how digoxin blocks Na/K ATPase and has yellow eyes, a side effect of digoxin toxicity.
AntiarrhythmicDIG = dig | OX = ox | IN = in
HOW STEP TESTS IT
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Digoxin inhibits Na/K ATPase, causing intracellular sodium to accumulate. The cell normally uses the Na/Ca antiporter to pump calcium out by bringing sodium in, but with sodium already high inside, this exchanger slows down. Calcium stays trapped inside the cell, increasing contractility. Digoxin also increases vagal tone, slowing heart rate.
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Side Effects: Digoxin is renally excreted - anything that impairs kidney function, including NSAIDs or aminoglycosides, can cause toxicity even at a normal dose. Toxicity presents with yellow-green vision, bradycardia, and heart block.
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A 68-year-old woman with chronic heart failure is stable on digoxin. She is started on ibuprofen for knee osteoarthritis. Two weeks later, her digoxin level is significantly elevated. What is the mechanism?
Answer & Explanation C - NSAIDs block prostaglandins that maintain afferent arteriole dilation. GFR drops and digoxin clearance falls, causing digoxin toxicity.