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?
- A)Increased bioavailability
- B)Decreased efficacy
- C)Increased potency
- D)Increased volume of distribution
- E)Decreased clearanceGABARITO
Explicação
Clearance is the volume of plasma from which a drug is completely removed per unit time. Renal failure reduces elimination of renally excreted drugs, so clearance falls and plasma concentration rises, predisposing to toxicity at standard doses. Ver explicação completa e trilha adaptativa →