Patients on warfarin should not use over-the-counter Miconazole oral gel (Daktarin)

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Miconazole oral gel indicated for first-line treatment for localised or mild oral candida (oral thrush) infection in children (aged over 4 months) and adults.

Two miconazole oral gel products are authorised in the UK:

  • Daktarin Oral Gel is classified as a prescription-only medicine (POM)

  • Daktarin Oral Gel Sugar Free 2% is classified as a pharmacy (P) medicine available without prescription but only from pharmacies, supplied by or under the supervision of a pharmacist.

Warfarin an oral anticoagulant indicated for prophylaxis of thromboembolic events. Daily dose depends on individual requirements and patients receiving therapy require regular coagulation tests.

The antifungal drug miconazole inhibits several P450 isozymes, including CYP2C9, which heightens the anticoagulant effect of warfarin leading to an increase in international normalised ratio (INR) values and subsequent bleeding complications. The potential for an interaction between miconazole and warfarin is documented in published literature, because of this, warnings are given in the Summaries of Product Characteristics about the potential for drug interactions between anticoagulants/warfarin and azole antifungals hence the anticoagulant effect should be carefully monitored.

In March 2016, the Medicines and Healthcare products Regulatory Agency (MHRA) received a Prevention of Future Deaths (regulation 28) report from a coroner regarding the death of a patient from intracerebral haemorrhage. The coroner raised concerns about the risks for a drug interaction between miconazole oral gel and warfarin, and a possible lack of awareness of the interaction among healthcare professionals.

In response to the report, MHRA initiated a review of available data about this interaction. The Commission on Human Medicines was asked to advise on whether measures were needed to minimise risk to patients. While further measures were being considered, an article in Drug Safety Update cautioned that miconazole oral gel is systemically absorbed and can enhance the anticoagulant effects of warf...