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

Considerations for healthcare professionals (2,3)

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?

Practical advice for healthcare professionals (2,3)

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 an IM injection is required and other options are unsuitable:
  • consider administration before the next dose of anticoagulant rather than immediately after a dose (delaying anticoagulant dosing may be possible)
  • administer into an upper extremity to allow easy access for manual compression, inspection of bleeding, and/or to apply pressure bandages if needed
  • use a fine needle (23 or 25 gauge)
  • apply firm pressure for at least 2 to 5 minutes after the injection
  • advise the person to watch out for bleeding at or around the injection site and for signs of haematoma for example, pain and swelling

Advice in product prescribing information

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.

For more detailed advice then click here

Note that IM injection should be performed by medically trained personal (1)

• for IM route, the injection should be performed in the deltoid muscle, with a fine needle (23 - gauge at least)
• a firm pressure, without rubbing, at the injection site should be maintained 2 to 5 minutes after SC or IM injection
• the patient or family should be given information on the risk for hematoma from the injection.

Reference:

• 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
• NHS Specialist Pharmacy Service (September 2023). Using intramuscular injections in people on oral anticoagulants