Warfarin : raised INR NICE guidance

When managing a patient whose International Normalized Ratio (INR) is outside the therapeutic range, it is crucial to conduct a thorough assessment to identify possible causes for the variation. This assessment should encompass the following aspects:

1. Adherence to Warfarin: Confirm if the patient has been consistent with their warfarin dosing schedule, including any missed doses or accidental overuse.

2. Concomitant Medications: Review any additional medications the patient may be taking. This includes prescribed drugs, over-the-counter products, vitamins, and any herbal or homoeopathic remedies, as they may interact with warfarin and affect its anticoagulant effect.

3. Substance Use: Inquire about the intake of alcohol or the use of illicit drugs, which can alter warfarin metabolism and effectiveness.

4. Dietary Habits: Dietary intake, particularly foods rich in vitamin K (such as green vegetables) and cranberry juice, can influence warfarin activity and should be evaluated.

5. General Health Status: Take into account the patient’s overall health. Factors such as weight loss, acute illnesses (like gastroenteritis), and cessation of smoking may potentiate the effects of warfarin. Conversely, weight gain, episodes of diarrhoea, and vomiting can diminish its anticoagulant impact.