Beta Blockers USMLE Step 1 Practice Question
A 72-year-old man with a history of chronic kidney disease stage 4, hypertension, and heart failure with reduced ejection fraction presents to his cardiologist for a routine follow-up. His blood pressure is 158/94 mmHg and heart rate is 96 beats per minute. He is started on atenolol, a renally excreted beta-blocker, at a standard dose of 50 mg daily. Two days later, he presents to the emergency department with profound bradycardia (heart rate 38 bpm), hypotension, and fatigue. Laboratory studies reveal a serum creatinine of 4.8 mg/dL and a creatinine clearance of 12 mL/min, far below the normal range of 90–120 mL/min. Which of the following pharmacokinetic changes most directly explains the rise in plasma drug concentration?
Answer choices
- AIncreased bioavailability
- BDecreased efficacy
- CIncreased potency
- DIncreased volume of distribution
- EDecreased clearanceCorrect answer
- FIncreased renal reabsorption
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