It’s only a mouth gel — so why is her INR now 8?
Miconazole oral gel is swallowed, and it greatly increases warfarin’s effect. It is sold over the counter.
Select any card for the reasoning, what to watch for and an exam tip.
The puzzle
An 80-year-old woman takes warfarin for atrial fibrillation. Her denture-sore mouth turns out to be thrush, and she buys miconazole oral gel. A week later she has nosebleeds and large bruises, and her INR is 8.
The answer, step by step
Who is most at risk
- Anyone on warfarin who buys a remedy for oral thrush.
- Older people and denture wearers, who are prone to oral thrush.
- Patients whose INR is checked only every few weeks.
- Other vitamin K antagonists: acenocoumarol and phenindione.
What to do
Key takeaway
Miconazole oral gel is not just a local treatment: it greatly increases the effect of warfarin. Avoid it unless the INR can be monitored closely, and ask every customer with thrush whether they take warfarin.