PTCB Certified Pharmacy Technician (PTCE)Patient Safety and Quality AssuranceMedium
A pharmacy technician is preparing a patient's medication profile for pharmacist review. The patient is prescribed 'Coumadin (warfarin) 5 mg daily' and 'Bactrim DS (sulfamethoxazole/trimethoprim) twice daily.' The technician recognizes a potential drug interaction. Which type of interaction is MOST likely occurring?
- ASynergistic effect leading to enhanced anticoagulant activity.
- BAntagonistic effect leading to decreased antibiotic efficacy.
- CAdditive effect leading to increased sedation.
- DPrecipitation leading to reduced absorption in the GI tract.
Show answer & explanationAnswer & explanation
Correct answer: A. Synergistic effect leading to enhanced anticoagulant activity.
Sulfamethoxazole/trimethoprim (Bactrim DS) is known to significantly inhibit the metabolism of warfarin, leading to increased warfarin levels and a heightened risk of bleeding (enhanced anticoagulant activity). This is a critical drug-drug interaction that requires immediate pharmacist intervention.
Why the other options are wrong
- B. The interaction does not primarily involve decreased antibiotic efficacy.
- C. This interaction does not typically cause increased sedation.
- D. This interaction is not characterized by precipitation and reduced GI absorption.
Warfarin-Antibiotic Interaction
Certain antibiotics, like sulfamethoxazole/trimethoprim, can enhance the anticoagulant effect of warfarin, increasing bleeding risk.
- Warfarin is a narrow therapeutic index drug.
- Many drugs interact with warfarin.
- Antibiotics can alter gut flora or inhibit metabolism.
Memory trick: Bactrim + Warfarin = Bleeding Alarm!