High risk medicines: anticoagulants

Anticoagulants are medicines that help prevent the blood from clotting as normal.

They treat and prevent blood clots. Examples of anticoagulants include:

• warfarin
• non-vitamin K antagonist oral anticoagulants, also known as direct oral anticoagulants (DOACs) or novel oral anticoagulants (NOACs). These include: 
  • apixaban
  • rivaroxaban
  • edoxaban 
  • dabigatran
• injectable anticoagulants, also known as low molecular weight heparins.

The most common side effects of all anticoagulants are bleeding and bruising. They are critical medicines and must be given at the prescribed times to make sure they are effective.

Information and awareness

People taking anticoagulants should have accessible information to use them safely and effectively. The NICE guideline on venous thromboembolic diseases says that people should know:

• how to use anticoagulants
• how long to take anticoagulation treatment
• possible side effects of anticoagulant treatment and what to do if these occur
• the effects of other medicines, foods and alcohol on oral anticoagulation treatment
• how to monitor their anticoagulant treatment
• how anticoagulants may affect their dental treatment
• what to do if they are planning pregnancy or become pregnant
• how anticoagulants may affect activities such as sports and travel
• when and how to seek medical help.

Include this information in a care plan to support the use of anticoagulants. Add guidance about what to do if a person misses a dose.

Injectable heparins

These are often prescribed for prevention of blood clots in patients after surgery.

Injectable heparins are normally prescribed as pre-filled syringes. The person can administer these by subcutaneous injection. Manufacturers recommend rotating the site of administration.

If a person cannot self-administer the injection, a healthcare professional may administer. Or you can ask a care worker to do this. You must provide relevant training and assess the competency of care workers who accept this responsibility. A care plan should be in place to support this delegated task.

For more information, see Delegating medicines administration.

Dispose of used syringes in a sharps bin. See Handling sharps in adult social care for more information. 

Non-vitamin K antagonist oral anticoagulants (DOACs)

Give DOACs at the prescribed dose and frequency. Their duration of action is shorter than that of warfarin. The anticoagulant effect of DOACs fades 12 to 24 hours after taking the last dose. Omitting or delaying doses could lead to a reduction in anticoagulant effect. This would cause a higher risk of blood clots.

Some DOACs can be given once or twice a day depending on why a person needs them.

If someone misses a dose of a DOAC, you need to know what action to take and record this. For example, you should contact a healthcare professional for advice about taking the next dose. You should also inform the person’s prescriber.

People who take DOACs and injectable anticoagulants must have blood tests both:

• before starting treatment, and
• at intervals throughout treatment as specified by the prescriber.

Warfarin

People taking warfarin need regular blood tests. Support people to access monitoring and testing where necessary.

Blood tests are more frequent at the start of treatment to ensure the person is on the correct dose. They may become less frequent once the person is on stabilised treatment.

The maximum time between blood tests is 12 weeks.

Regular blood tests measure the International Normalised Ratio (INR). This is a measure of how fast the blood clots. A person can get INR blood tests at their GP practice or hospital. Specialist clinics might test blood depending on the services they provide.

The dose prescribed often changes in response to the result of the blood test, so it is often prescribed 'as directed'. Make sure you are aware of the person's current warfarin dose.

The National Reporting and Learning System issued an alert to highlight the importance of warfarin compliance and monitoring. Everyone who is taking warfarin should receive a copy of 'the yellow book'.

The booklet includes a section to write a record of warfarin dose and explains important information about:

• the medicine
• how to take it
• how to recognise side effects
• how to keep track of ongoing blood monitoring.

INR blood test results should be in writing. This could be in the patient's handheld yellow INR record book. Or the results could be in direct written communication from the prescriber.

The person should usually take warfarin at the same time each day.

If you are responsible for administering warfarin, record exactly how much you give each time. You can do this on the MAR or on other appropriate forms.

If a person takes too much or too little warfarin, you must contact their GP.

Warfarin interacts with many medicines. This includes over-the-counter medicines and herbal products. If a person starts a new medicine, the GP and pharmacist should check for any interactions. If the person needs any over-the-counter medicines, you must consult a pharmacist first. They need to know that the person is on warfarin. Also refer to the yellow book for information on how certain foods can affect INR levels.

People should not consume large amounts of alcohol when taking warfarin.

Be aware of known side effects of warfarin. These include:

• spontaneous, severe or prolonged bruising
• blood in the urine or faeces.

For more detail on side effects, see Warfarin (NHS).

Always tell the appropriate healthcare professional if the person taking warfarin has a fall as they are at a higher risk of internal bleeding. Often, they will need to be managed or assessed in secondary care.

Prescribers may decide to switch people from warfarin to a DOAC to reduce the need for blood tests.

People should not be taking both warfarin and a DOAC. If you see this combination, check with the prescriber before administering.