Drug of the Week Series - 19.2

General
1

Scenario:
A 65-year-old patient taking warfarin for atrial fibrillation is prescribed a new medication. The physician wants to check for a possible drug interaction.

Poll:
Which of the following can significantly affect warfarin’s anticoagulant effect?

  • Paracetamol
  • Antibiotics such as trimethoprim-sulfamethoxazole
  • Calcium carbonate
  • Oral rehydration solution
0 voters

Question:
Why can certain antibiotics increase the risk of bleeding in patients taking warfarin?
What do you think?

MBH/PS

2

I guess trimethoprim and sulfsmethoxazole..

Am I right???

3

Warfarin is an anticoagulant. Antibiotics like sulfamethoxazole-trimethoprim(Bactrim),ciprofloxacin, metronidazole etc. prevent its breakdown in liver; increases warfarin concentration in blood stream, making your blood thinner than it should be..

4

It is due to enzyme inhibition (CYP450)….which decreases metabolism of warfarin and increases its concentration in blood … which causes bleeding