Sir, we would like to remind clinicians to be mindful of drug interactions when prescribing common anti-infective medications. A warfarinised patient in the 65+ age group was prescribed a course of Daktarin (miconazole nitrate 2% topical gel) for oral candidiasis by their general practitioner, subsequently developing spontaneous bruising on the upper and lower limbs, with the INR increased to 10.
The patient was brought into the Acute Medical Unit for vitamin K therapy to bring the INR back into the targeted range of 2-4 and their warfarin was withheld. The interaction was addressed and promptly managed, avoiding any significant complications. However, the patient did require hospitalisation which should not be taken lightly, especially given the risks of COVID-19 transmission.
Miconazole and other -azole antifungal medications (including topical form) greatly potentiate the anti-coagulant effect of warfarin and can have fatal consequences if bleeding occurs. The interaction is graded as severe and clinicians should avoid prescribing unless essential, with close INR monitoring.
We kindly remind all clinicians to double check interactions for drugs when prescribing, even if they are in topical form, and to continue to use the BNF for reference.