Warfarin and other anticoagulants: monitoring of patients during the COVID-19 pandemic

Guidance has been published on monitoring of patients on warfarin and other anticoagulants during the COVID-19 pandemic.

Following concerns raised by clinicians during the coronavirus (COVID-19) pandemic, we have issued advice to healthcare professionals and patients regarding the safe use of warfarin and other anticoagulants. This advice has been endorsed by the Commission on Human Medicines (CHM).

Healthcare professionals are reminded that:

  • acute illness may exaggerate the effect of warfarin and necessitate a dose reduction; patients on warfarin or other vitamin K antagonists should therefore be asked to tell their GP or healthcare team if they have symptoms of, or confirmed, COVID-19 infection

  • continued INR (international normalised ratio) monitoring is important in patients taking warfarin or other vitamin K antagonists if they have suspected or confirmed COVID-19 infection, so they can be clinically managed at an early stage to reduce the risk of bleeding

  • both vitamin K antagonists and direct-acting oral anticoagulants (DOACs) may interact with other medicines and if a patient using these oral anticoagulants is also prescribed antibiotics or antivirals, follow advice in the product information for minimisation of risk of potential interactions – this includes INR monitoring in patients taking vitamin K antagonists who have recently started new medicines

  • if patients are switched from warfarin to a DOAC, warfarin treatment should be stopped before the DOACs is started to reduce the risk of over-anticoagulation and bleeding

  • patients taking vitamin K antagonists should be reminded to carefully follow the instructions for use for anticoagulant medicines (including the patient information leaflet) and to tell their GP or healthcare team if they:

    • are otherwise unwell with sickness or diarrhoea or have lost their appetite
    • are taking any new medicines or supplements
    • have changed their diet, smoking habits, or alcohol consumption
    • are unable to attend their next scheduled blood test for any reason, including because they feel unwell.

Report on a Yellow Card

Suspected adverse drug reactions should be reported to the Yellow Card scheme. Any suspected adverse drug reactions associated with any medicine used in patients with confirmed or suspected COVID-19, including medicines to manage long-term or pre-existing conditions such as anticoagulant medicines, should be reported to the COVID-19 Yellow Card reporting site.

Article citation: Drug Safety Update volume 14, issue 3: October 2020: 5.

Published 22 October 2020