A 67-year-old woman with atrial fibrillation presents with dysuria, frequency, and suprapubic pain. Vitals: BP 138/82, HR 92, RR 16, Temp 38.2°C, SpO2 98%. Urinalysis shows pyuria and bacteriuria; urine culture pending. She takes warfarin (INR 2.3 baseline) for anticoagulation. Ciprofloxacin 500 mg orally twice daily is initiated for presumed UTI. Within one week, INR increases to 4.8 without dietary changes. Which mechanism best explains this drug interaction?
- A)Fluoroquinolones enhance hepatic production of vitamin K-dependent clotting factors
- B)Ciprofloxacin inhibits CYP2C9, reducing warfarin metabolismGABARITO
- C)Ciprofloxacin inhibits warfarin protein binding, increasing free warfarin levels
- D)Ciprofloxacin increases warfarin absorption through enhanced GI motility
- E)Ciprofloxacin displaces warfarin from renal tubular reabsorption sites
Explicação
Fluoroquinolones, particularly ciprofloxacin, inhibit CYP2C9, the primary enzyme responsible for warfarin metabolism. This reduces warfarin clearance, increases plasma levels, and prolongs the INR. This is a clinically significant interaction requiring INR mon... Ver explicação completa e trilha adaptativa →