Cardiovascular Drugs USMLE Step 1 Practice Question
A 67-year-old man with heart failure and atrial fibrillation on digoxin 0.25 mg daily and furosemide presents with nausea, palpitations, and visual halos. Vital signs: BP 128/76 mmHg, HR 102 bpm with irregular rhythm, RR 18, Temp 37°C, SpO2 98%. Serum potassium is 3.0 mEq/L; digoxin level is 2.8 ng/mL (therapeutic: 0.5-2.0). Troponin is normal. Which mechanism explains this drug toxicity?
Answer choices
- AHypokalemia competitively blocks digoxin cardiac receptors
- BHypokalemia increases hepatic metabolism of digoxin
- CHypokalemia increases Na-K-ATPase inhibition by digoxinCorrect answer
- DHypokalemia decreases digoxin protein binding
- EHypokalemia increases renal clearance of digoxin
- FHypokalemia decreases digoxin volume of distribution
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