Registered Charity number 1090250
PO Box 405 Bromley Kent, BR2 9WP Tel/Fax: 020 8289 6875 Email: anticoagulation@ntlworld.com Web site: www.anticoagulationeurope.org
Warfarin Interactions Warfarin is subject to many different types of interactions. Drug - drug Drug – disease Drug – food 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. 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 you pharmacist that you are on anticoagulation therapy before buying over the counter medicines. Tel 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 altogether. A balanced, healthy and consistent diet, with no dramatic changes, is the best one for you.
Name
Potential problem
Alcohol Alfalfa Allopurinol Aminoglutethamide Amiodarone Amitriptyline Anabolic Steroids (e.g. danazol, stanozolol) Angelica Aniseed Anti-epileptics Anti-fungals Arnica Aspirin Azaproprazone Azathioprine Barbiturates (e.g. Phenobarbital) Beta blockers Bezafibrate Bilberry Boldo
Increases anticoagulant effect of warfarin Increase effect of warfarin Increases anticoagulant effect of warfarin Reduces anticoagulant effect of warfarin Increases anticoagulant effect of warfarin Unpredictable increase or reduction in anticoagulant effect Increases anticoagulant effect of warfarin
Carbamazepine Cefaclor Celecoxib Chamomile Chloramphenicol
Coenzymne Q10
Reduces anticoagulant effect of warfarin Increases anticoagulant effect of warfarin Increases anticoagulant effect of warfarin Increases the effect of warfarin Increases anticoagulant effect Increases anticoagulant effect of warfarin May increase the anticoagulant effect of warfarin Increases anticoagulant effect of warfarin Increases anticoagulant effect of warfarin Increases anticoagulant effect of warfarin Increased risk of bleeding, even though INRs remain stable and within range. Reduces anticoagulant effect of warfarin by preventing the absorption of warfarin. Reduces anticoagulant effect
Co-proxamol
Increases anticoagulant effect of warfarin
Co-trimoxazole (Septrin) Corticosteroids
Increases anticoagulant effect of warfarin
Cranberry Juice
Increases anticoagulant effect of warfarin ADVISED NOT TO DRINK
Cimetidine Ciprofloxacin Ciprofibrate Clarithromycin Clofibrate Clopidogrel Colestyramine
May increase the effects of warfarin May increase the effects of warfarin May reduce the anticoagulant effect of warfarin May increase effect of warfarin May increase the effects of warfarin Increases anticoagulant effect of warfarin Increases anticoagulant effect of warfarin Reduces anticoagulant effect of warfarin Reduces anticoagulant effect of warfarin Generally no reaction. Check INR if prescribed Propranolol Increases anticoagulant effect of warfarin May increase the effect of warfarin May reduce anticoagulant effect of warfarin
Variable response
Cytotoxics Danazol (Danol) Dandelion Danshen Devil’s Claw Dexamethasone Dextromethorphan Diclofenac Diflunisal Dipyridamole Disulfiram Dong quai (Angelica sinensis) Erythromycin and Clarithromycin Esomeprazole Eveming Primrose Oil Fenofibrate Fenugrek Feverfew Fibrates Fish Oils Flax Seed oil Fluconazole
Increases anticoagulant effect of warfarin reported with some cytotoxics Increase anticoagulant effect of warfarin Increases anticoagulant effect of warfarin Increases anticoagulant effect of warfarin Increases anticoagulant effect of warfarin Can increase and decrease effect of warfarin. High doses increase effect May increase the effect of warfarin May increase risk of bleeding. Increases anticoagulant effect of warfarin Mild bleeding sometimes occur even though INRs remain stable and within range. Increases anticoagulant effect of warfarin Reports of marked increases anticoagulant effect of warfarin Increases anticoagulant effect of warfarin May increase risk of bruising and bleeding Increases anticoagulant effect of warfarin May increase bleeding Increases effect of warfarin Increases anticoagulant effect of warfarin May increase risk of bleeding May increase risk of bleeding Increases anticoagulant effect of warfarin
Flurbiprofen Flutamide Flu vacine Fluvastatin Garlic
Cases of bleeding reported with concomitant use. Increases anticoagulant effect of warfarin May increase INR test within 7 days Increases effect of warfarin Case reports of increased anticoagulant effect of warfarin
Gemfibrozil Gingko Biloba Ginseng
Increases anticoagulant effect of warfarin Isolated reports of increased risk of bleeding Reports of spontaneous bleeding in patients using Ginseng without anticoagulants May increase the effects of warfarin Large doses (>50mg over 2 days) increase anticoagulant effect of warfarin Increased risk of bleeding
Ginger Glucagon Glucosamine and or Chondroitin Grapefruit or Juice Green Tea
Inhibits meatabolism of warfarin and may increase INR levels
Griseofulvin Ibruprofen Indometacin Influenza vaccine Itraconazole Ketoconazole (Nizoral) Ketorolac (oral) Lansoprazole Liquorice Meadowsweet Mefanamic Acid Menthol Metronidazole (Flagyl) Miconazole (Daktarin) including oral gel Mitrazepine Nettle Non-Steroidal Antiinflammatory Drugs (NSAIDs) Ofloxacin Omeprazole (Losec) Orlistat Oral contraceptives Papaya Paracetamol Parsley Passion flower Penicillins Phenobarbitone Phenytoin Piroxicam A non steroidal anti-inflamatory drug NSAID Propafenone Prednisolone Quinidine Raioxfene Red Clover Rifampicin / Rifabutin Rosuvastatin
Reduces anticoagulant effect of warfarin Increases effect of warfarin Indomethacin inhibits platelet aggregation and so prolongs bleeding. Usually safe & uneventful, but small numbers of bleeding episodes reported. Case report of increased anticoagulant effect of warfarin Case reports of increased anticoagulant effect of warfarin Serious risk of gastro-intestinal bleeding May increase risk of bleeding Known to increase effect warfarin therapy Increases effect of warfarin Increases effect of warfarin May decrease the effect of warfarin Increases anticoagulant effect of warfarin Increases anticoagulant effect of warfarin Increases effect of warfarin Increases effect of warfarin NSAIDs irritate stomach lining and reduce platelet aggregation Unpredictable, requires careful monitoring Increases anticoagulant effect of warfarin Unpredictable, manufacturer recommends close monitoring Reduces effect of warfarin avoid in thromboembolic disorders Increases anticoagulant effect of warfarin Increases anticoagulant effect of warfarin when large doses are used over a prolonged time. Increases effect of warfarin therapy Increases effect of warfarin therapy Increases and decreases in the anticoagulant effect of warfarin have been seen. Greatly reduces effect of warfarin. Can require 60% dose increase Can increase or reduce anticoagulant effect of warfarin Increases anticoagulant effect of warfarin
May increase risk of bleeding May reduce or enhance effects – high doses enhance May increase effect of warfarin May reduce effect of warfarin May increase effect of warfarin therapy Markedly reduces anticoagulant effect of warfarin Increased risk of bleeding
Simvastatin
May increase INR check within 7 days of starting
St John’s Wort
Reduces the effect of warfarin
Sulphinpyrazone Sulphonamides Sulindac Tamoxifen Tumeric Thyroid hormones (Thyroxine) Tramadol Trimethoprim
Increases anticoagulant effect of warfarin Increases anticoagulant effect of warfarin Increases anticoagulant effect of warfarin Markedly increases anticoagulant effect of warfarin May increase effects of warfarin therapy Increases anticoagulant effect of warfarin
Venlafaxine Vitamin C Vitamin E Vitamin K Multi vitamins
Increase anticoagulant effect of warfarin May decrease effect of warfarin May increase effect of warfarin Anticoagulant effects of warfarin are reduced or abolished CAUTION Some multi vitamins contain vitamin K
Increases effect of warfarin Increases anticoagulant effect of warfarin
Minimizing Your Risk Keep your health professional up to date about the medications and natural health products you use, including vitamins, minerals and herbal products.
Taking warfarin, •
take the prescribed dose of warfarin at the same time each day
•
have your blood tested regularly for its clotting time
•
talk to your health care professional if you are going to start taking any new prescribed drug or over the counter medicine and/or natural health products, because your dose of warfarin may have to be adjusted
•
if you are already taking a drug and/or natural health products and warfarin, do not change your routine unless you have discussed it with your health care professional
•
ask your health care professional about foods that may change the effects of warfarin or have a direct effect on blood clotting
•
if you eat or drink food products that can change the effects of warfarin, be sure to keep your intake levels consistent from day to day
•
if you have any unusual bruising or bleeding, contact your health care professional for advice right away.
•
This leaflet does not replace advice given by your doctor or nurse. If in doubt about anything ask your health care professional.
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
Foods and warfarin Vitamin k will be found in foods such as liver, broccoli, brussel sprouts and green leafy vegetables such as spinach, chard, coriander, watercress and cabbage. Beef liver and pork liver are also high in vitamin K. Foods that are low in vitamin K include cauliflower, green beans, carrots, celery, onions, potatoes, cucumber, mushrooms, pumpkin, tomato, corn, peppers, apples, blueberries, lemons, oranges, melons, peaches, grapefruit, mackerel, shrimp and tuna. Fats and oils that are low in vitamin K include peanut oil, corn oil, sesame oil and sunflower oil. Olive oil and margarine contain medium levels of vitamin K. See attached list. This does not mean that you should not eat them. It is important to maintain a healthy diet. You should be consistent in what you eat and drink and avoid sudden changes in your daily intake of any of these foods.
AntiCoagulation Europe is a registered charity committed to the prevention of thrombosis providing help, advice and information to people on anticoagulant and antiplatlet therapy. For more information about the charity, to make a donation or to receive a free copy of our quarterly magazine INReview please write to the address below, email or phone. AntiCoagulation Europe PO Box 405 Bromley, Kent BR2 9WP Tel: 0208 289 6875 Email: anticoagulation@ntlworld.com Web site: www.anticoagulationeurope.org
Please note that this list was updated in December 2012