Providers are strongly advised to seek support from district nurses and/or the Pharmacy Support Team prior to and during supporting service users with Warfarin because this drug requires extra caution.

What Warfarin is

Warfarin is an anticoagulant (blood thinner). It reduces the formation of blood clots and is used to treat or prevent blood clots in veins or arteries, which can reduce the risk of stroke, heart attack, or other serious conditions.

Staff should be vigilant and aware of arrangements for individual service users.

How Warfarin works

Warfarin decreases the body's ability to form blood clots by blocking the formation of vitamin K that is needed to make clotting factors and prevent bleeding. Warfarin stops harmful clots from forming and prevents clots from getting larger.

Importance of taking Warfarin at the same time of day

It is important that the service user takes their Warfarin medication at the same time each day, before, during or after a meal.

If for any reason the service user does not take it at their normal time, they need to take it as soon as they can and then continue taking it as normal.

It is important not to take a double dose to catch up unless their GP has specifically advised to do so and further medical advice should always be sought if any dose is missed or there is any doubt about giving a dose at a later time than usual.

If staff are in any doubt or have any concerns about a service users Warfarin, they must contact a health care professional immediately. (District nurse, the service users GP or pharmacist)

Warfarin interactions with alcohol and certain foods

Alcohol intake can affect how the body metabolizes Warfarin and so anyone taking Warfarin should avoid drinking alcohol altogether.

Eating an increased amount of foods rich in Vitamin K can make Warfarin less effective and potentially increasing the risk of blood clots. The highest amount of vitamin K is found in green and leafy vegetables such as broccoli, lettuce, and spinach. It is not necessary to avoid these foods. However, it is important that they are not eaten in excessive amounts.

Possible side effects

If the service user taking Warfarin experiences the following signs of bleeding, staff should seek further medical advice and inform their line manager immediately.

  • Severe headache, confusion, weakness, or numbness
  • Coughing up large amounts of bright red blood
  • Vomiting blood
  • Bleeding that will not stop
  • Bright red blood in stools
  • Fall or injury to the head
  • Headache that is severe or unusual

Signs of unusual bleeding including:

  • bleeding from the gums
  • blood in the urine
  • bloody or dark stool
  • a nosebleed
  • vomiting blood

Warfarin interactions with other medications

Many medications can alter the effectiveness of Warfarin, including some of the most common over-the-counter medications such as aspirin, ibuprofen, and naproxen.

Herbal medicines and supplements can also interact with Warfarin.

The service user should therefore avoid taking other medications without first checking with their GP or pharmacist.

Other key points that are essential for providers to ensure they follow when supporting a service user with Warfarin (or any anticoagulant medication)

  • Staff need to be familiar with the different colours of Warfarin tablets and the various strengths which collectively may be required to make up a specific dose.
  • Staff need to be trained and competency assessed by a suitably trained and competent person before supporting a service user with Warfarin and any other medications.
  • Risk assessments and safe practices must in place before support is provided, to reduce and minimise risks to staff and service users.
  • The providers' medication policy and procedures need to include a section on the administration and support of anticoagulants, including Warfarin.
  • There needs to be a safe system in place to ensure information on service users latest blood results (otherwise known as INR - International Normalized Ratio) and latest prescribed dose of Warfarin are available and accessible for staff to follow. This information is usually recorded in the service user's anticoagulant treatment booklet, usually a 'Yellow Book'. This information and the MAR (Medication Administration Record) need to be cross-referenced for correlation so that the service user is taking the correct dose.
  • It is important to understand that unlike most medications that are prescribed as a fixed dose, Warfarin doses are adjusted according to blood test results. Therefore, staff always need to double-check the most recent INR test result report when giving a dose - it is essential that dosages are not given from old INR reports.
  • The number of milligrams (mg) of Warfarin required needs to be stated on the MAR, NOT the number of tablets.
  • The National Patient Safety Agency (NPSA) recommends that oral anticoagulants are administered from the original packs dispensed for individual patients. Multi Compartment Compliance Aids (Dossett's) are not flexible enough to cope with frequent dose changes and are not recommended for anticoagulants.
  • There should also be a process in place to follow up results if they have not been received within 3 days. If the service user has not received the record within 3 days, or there are any queries or concerns regarding results or doses then the anticoagulation service should be contacted using the telephone number provided on the INR test forms.
  • Medical advice will need to be sought from the service user's pharmacy or GP in the event of a missed or refused dose. (Please note - Service users may need to stop taking Warfarin if they are having surgery, dental work, or other medical procedures but MUST only be stopped if confirmed in writing by the relevant health professional).
  • A record must be made in the service users anticoagulant treatment booklet/yellow book and the Medication Administration Record (MAR) of any missed or refused doses (within the last two weeks will affect the blood test results and so the anticoagulant service MUST be informed of any missed Warfarin).
  • It is advisable for all information relating to the service users Warfarin to be kept together as if the person is transferred to another health or social care setting, the yellow book (or equivalent anticoagulant clinic record log), INR result sheets, a copy of the MAR and any other information received MUST be sent with the service user.
  • It is good practice to attach the written oral anticoagulant dosage supplied by the clinic to the MAR chart.

Warfarin administration recording form

Warfarin Administration Recording

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