A 72-year-old woman with a CD4 count of 45 cells/μL presents to the emergency department with palpitations and dyspnea on exertion. She was started on azithromycin 1200 mg weekly 5 days ago for Mycobacterium avium complex (MAC) prophylaxis. Her current medications include digoxin 0.25 mg daily for systolic heart failure. Vital signs: HR 128 bpm and irregular, BP 98/62 mmHg, RR 22/min, temperature 37.1°C. Serum digoxin level is 3.2 ng/mL (therapeutic range 0.8–2.0 ng/mL). Serum potassium is 4.1 mEq/L, serum creatinine is 0.9 mg/dL, and serum magnesium is 2.0 mg/dL. Electrocardiography reveals atrial fibrillation with a rapid ventricular response and nonspecific ST changes. Which of the following best explains the elevated serum digoxin concentration?
- A)Azithromycin-induced hypokalemia and hypomagnesemia potentiating digoxin cardiotoxicity
- B)Inhibition of P-glycoprotein-mediated renal tubular secretion of digoxinGABARITO
- C)Inhibition of cytochrome P450 3A4-mediated hepatic metabolism of digoxin
- D)Increased digoxin absorption due to azithromycin-induced gastric pH elevation
- E)Azithromycin metabolite-mediated direct inhibition of Na+/K+-ATPase activity
Explicação
Azithromycin is a potent inhibitor of P-glycoprotein, an efflux transporter in the renal tubule and intestinal epithelium. Digoxin is a substrate for P-glycoprotein; inhibition of this pump reduces renal and biliary clearance, leading to increased serum digoxi... Ver explicação completa e trilha adaptativa →