risks of intramuscular injections in people taking oral anticoagulants
Risks of intramuscular injections in people taking oral anticoagulants
Increasing numbers of people are prescribed oral anticoagulant medicines such as warfarin, or one of the newer direct oral anticoagulants (DOACs): apixaban, dabigatran, edoxaban, or rivaroxaban, to treat or prevent blood clots.
Most of these people will need to receive an IM injection at some stage.
Due to their increased bleeding tendency, people taking oral anticoagulant medicines may be at increased risk of bleeding complications related to IM injections such as bruising or haematomas (collection of blood that has leaked from blood vessels into tissues, organs or other body spaces).
There have also been occasional reports of compartment syndrome with injections into deeply located muscles.
Intramuscular (IM) injections (injections into a muscle) are invasive procedures that can cause bruising or bleeding at the injection site (1)
- several national guidelines described the practical aspects of vaccination, including the issue of IM vaccination in patients under anticoagulants (1)
- concerning the bleeding risk associated with IM vaccination, the Public Health England addresses the specific case of administering COVID-19 vaccine to individuals taking anticoagulants
- stated that individuals on stable anticoagulation therapy, including individuals on VKA (vitamin K antagonists) who are up-to-date with their scheduled INR testing and whose latest INR was below the upper threshold of their therapeutic range, can receive IM vaccination
- if there is any doubt, a consultation with the clinician responsible for prescribing or monitoring the individual's anticoagulant therapy is recommended
Healthcare professionals may need to consider these factors:
- Is there an increased risk of adverse effects (e.g. bruising, haematoma)?
- Could the injection affect anticoagulant control?
- Could the anticoagulant alter the effectiveness of the injection?
When considering a small volume IM injection for a patient taking an oral anticoagulant:
- Avoid IM injections if possible. Do not administer an IM injection if INR is raised above the therapeutic range.
- Consider if alternative routes of administration are possible or if alternative treatment is appropriate
- If a small volume IM injection is necessary:
- Check the relevant Summary of Product Characteristics (SmPC) for the IM injection to be administered and for the oral anticoagulant the patient is taking
- Evaluate the risk-benefit ratio for the individual
- Administer the IM injection into an upper extremity as a precaution. This will allow easy access for manual compression, inspection of bleeding, and/or to apply pressure bandages if needed
- Use a fine needle and apply firm pressure for at least 2 minutes immediately after the injection
- Advise the patient to watch out for bleeding at or around the injection site and for signs of haematoma
Before administering an IM injection to a person taking an oral anticoagulant, healthcare professionals should consult the product prescribing information (SmPC) or other prescribing references such as the British National Formulary to guide them.
- Perrin G, Beller CL, Darnige L, et al. Intramuscular Vaccination in Adults with Therapeutic Anticoagulation in the Era of COVID-19 Vaccines Outbreak: A Practical Review. TH Open. 2021;5(2):e166-e170. Published 2021 May 25. doi:10.1055/s-0041-1729627
- NHS Specialist Pharmacy Service (May 2022).Small volume intramuscular injections in people taking oral anticoagulants
Last edited 05/2022 and last reviewed 05/2022