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PO Box 405 Bromley Kent, BR2 9WP Tel/Fax: 020 8289 6875 Email: anticoagulation@ntlworld.com Web site: www.anticoagulationeurope.org
Warfarin Interactions This guide is intended as a quick reference to highlight significant interactions between warfarin and commonly prescribed medicines or complimentary medicines and a list of the vitamin K content of some foods. It is not intended to be exhaustive or give detailed information. Reducing the effect of warfarin will lower your INR. Increasing the effect of warfarin will raise your INR. Always tell your anticoagulant clinic of any changes in medication whether prescribed or over the counter, as it may be necessary to alter your dose of warfarin, particularly when starting or stopping medication. Always tell your pharmacist that you are on anticoagulation therapy before buying over the counter medicines. Tell your clinic about significant changes in diet. If you are self-testing or self-managing the frequency of testing may need to be increased when starting or stopping medication. If in doubt consult your anticoagulation clinic. Changes in your condition, regardless of whether you need to take extra medication, can also affect your INR levels. For example conditions such as heart failure, trauma, infection, sickness and diarrhoea will affect warfarin control. So as much attention needs to be paid to illness as is paid to new medicines. A healthy diet is vital for all of us, whether on warfarin or not. It is important that you are aware of foods containing vitamin K but this does not mean that you should avoid them. A balanced, healthy and consistent diet, with no dramatic changes, is the best one for you. Vitamin k will be found in many foods. See attached list. Reporting of drug interactions – Yellow Card Both patients and health care professionals can report side effects and interactions to do with warfarin. If you detect an interaction with Warfarin (or any drug) we would strongly encourage you to complete a Yellow Card (ask your health care professional for one) or complete a report on the website at www.yellowcard.gov.uk