The UK regulatory agency MHRA has published recommendations for patients and healthcare professionals
King’s College Hospital in London contacted the Medicines and Healthcare products Regulatory Agency (MHRA) of the United Kingdom about its concern regarding an apparent increase in the number of patients taking warfarin who showed elevated international normalized ratio (INR) values during the COVID-19 pandemic.
The reasons for this are probably multifactorial. In most, but not all, of these patients, COVID-19 infection was suspected or confirmed, while others had recently been treated with antibiotics. For other patients, the authors suggest that isolation may have affected access to green leafy vegetables and led to increased alcohol consumption, while the psychological impact of social distancing and serious bereavement may have affected adherence to the usual use of regular medicines.
The MHRA agency has issued recommendations to healthcare professionals and patients on monitoring patients who take anticoagulants during the COVID-19 pandemic. Anticoagulant drugs help reduce the risk of blood clots.
The recommendations include a reminder to doctors to continue regular blood tests in patients taking warfarin or any other vitamin K antagonist who have developed an additional illness. Blood tests will show whether the anticoagulant dose needs to be changed. In particular, it is important that these regular blood tests are performed for any patients with symptoms of COVID-19 or who have tested positive for COVID-19, so that appropriate care can be provided to them at an early stage to reduce the risk of bleeding. Therefore, it is important that you or your caregivers tell your doctor whether you have tested positive for COVID-19 or are ill with COVID-19 (high temperature, new persistent cough, loss of sense of smell or taste).
The recommendations also include a reminder about the possibility of drug interactions between some oral anticoagulants in tablet form and medicinal products used to treat infections, for example antiviral drugs or antibiotics (such as doxycycline, amoxicillin, or clarithromycin, which may interact with warfarin or other vitamin K antagonists). Other anticoagulants in tablet form (including apixaban, dabigatran, edoxaban, or rivaroxaban) may also interact with certain medicinal products. These drug interactions may potentially enhance the blood-thinning effect of some anticoagulants and lead to a higher risk of bleeding.
Recommendations for healthcare professionals
Healthcare professionals are reminded that acute illnesses can enhance the effect of warfarin tablets and require a dose reduction. Therefore, continuous INR monitoring is important for patients taking warfarin or other vitamin K antagonists (VKA) if COVID-19 is suspected or confirmed in them, so that they can be treated clinically at an early stage to reduce the risk of bleeding.
Some patients who were taking warfarin may have switched to direct oral anticoagulants (DOACs) during the pandemic to avoid regular blood tests for INR monitoring. Healthcare professionals are aware that VKAs interact with a large number of medicinal products, but they are also reminded that direct oral anticoagulants (DOACs), including apixaban, edoxaban, dabigatran, or rivaroxaban, also interact with certain medicinal products.
Patients with COVID-19 may receive treatment with antibiotics in accordance with NICE recommendations, as well as with antiviral medicines. Therefore, healthcare professionals are reminded of the possibility of drug interactions between oral anticoagulants (i.e., VKA or DOACs) and certain antibiotics and antiviral medicines, and are advised to follow the existing requirements in the instructions for medical use. This includes recommendations on the need for INR monitoring in patients taking VKA who have recently started new medicines.
MHRA is also aware of a small number of patients whose warfarin treatment continued after the start of DOAC treatment. To reduce the risk of excessive anticoagulation and bleeding, healthcare professionals must ensure that warfarin treatment is discontinued before DOACs are started.
Recommendations for patients
Patients who undergo INR tests or receive prescriptions for VKA should be asked to inform their doctor if they have symptoms or a confirmed COVID-19 infection, since it is important that they continue to monitor INR while they are ill.
Patients taking VKAs should also be reminded to tell their doctor about any recent changes in their diet (including alcohol consumption), smoking, or the use of any new medicines or supplements, and about the need to follow the instructions for use of anticoagulant medicines carefully.
Patients taking VKA should also be instructed to inform their doctor if nausea, diarrhea or loss of appetite occurs, or if they are unable to attend the next scheduled blood test for any reason, including feeling unwell.
If you are taking warfarin or any other vitamin K antagonist, it is important to take your diet into account, as it may affect the efficacy of this medicine. Do not abuse alcohol while taking warfarin or any other vitamin K antagonist. Always take the daily dose at the same time, without chewing, and with a glass of water.
It is important to follow your doctor’s instructions and not to stop using or change the dosage of the medicinal products prescribed to you without an appropriate recommendation.
If you have any questions or concerns about this information regarding warfarin or other oral anticoagulants, you should discuss them with your doctor.
Link
https://www.gov.uk/government/news/warfarin-and-other-blood-thinners-reminder-on-safe-use-during-covid-19-pandemic
https://www.gov.uk/government/publications/warfarin-and-other-anticoagulants-monitoring-of-patients-during-the-covid-19-pandemic/warfarin-and-other-anticoagulants-monitoring-of-patients-during-the-covid-19-pandemic
