A 62-year-old woman with gastroesophageal reflux disease takes daily omeprazole. She is prescribed clarithromycin for H. pylori eradication as part of triple therapy. After 5 days, she develops palpitations, dizziness, and syncope. Vital signs show HR 110 bpm, BP 98/62 mmHg. ECG demonstrates QT prolongation (520 ms). Serum potassium is 3.1 mEq/L. She denies chest pain. Which mechanism best explains this adverse drug interaction?
- A)Clarithromycin blocks cardiac potassium channels directly, causing QT prolongationGABARITO
- B)Combined therapy causes hypomagnesemia, predisposing to arrhythmias
- C)Omeprazole increases gastric pH, reducing clarithromycin absorption
- D)Clarithromycin inhibits CYP3A4, increasing omeprazole levels and causing toxicity
- E)Omeprazole induces CYP1A2, decreasing clarithromycin metabolism and causing accumulation
Explicação
Clarithromycin is a macrolide antibiotic that directly blocks cardiac hERG potassium channels, prolonging the QT interval and increasing risk of torsades de pointes. This effect is dose-dependent and occurs regardless of omeprazole. The syncope suggests tachya... Ver explicação completa e trilha adaptativa →