QuestionSBA
QuestionChoice
Trauma is unlikely to increase INR and is absent in this patient. A patient with a raised INR may be at increased risk of bleeding as a result of trauma.
10006814
d
Trauma
QuestionChoice
Metformin has been shown to reduce INR, not increase it.
10006815
e
Metformin
QuestionChoice
A change in diet - specifically intake of more vitamin K-rich foods may result in a fall in INR, not a rise. This is because vitamin K acts as a natural reversal agent for warfarin - a vitamin K antagonist.
10006812
b
Increased green vegetable intake
QuestionChoice
Antibiotics (most notably macrolides and metronidazole) can increase INR by inhibiting warfarin's metabolism, and affecting gut flora and therefore vitamin K absorption. This patient is currently being treated for cellulitis, which is frequently treated with metronidazole, clarithromycin or erythromycin. These antibiotics are known to delay the metabolism of warfarin and therefore enhance its anticoagulant effect. This would result in a raised INR.
10006811
a
Antibiotic use
QuestionChoice
Paracetamol use is considered safe when used in combination with warfarin and would not increase the patient's INR. However, other over-the-counter medicines, such as aspirin and ibuprofen, have been shown to increase the effects of warfarin, increasing the INR.
10006813
c
Paracetamol use
Concept
Chapter
2693
4545
High INR
Topic
157
Haematology
13909
A 62-year-old female patient on long-term warfarin for atrial fibrillation presents to the INR clinic. Her INR on this occasion is found to be raised at 4.6. She has a past medical history of osteoarthritis which she manages with over-the-counter medicines, and type 2 diabetes for which she has recently been started on metformin. She reports that she is currently being treated for cellulitis.

Which of the following is most likely to have increased this patient's INR?
a