At Christmas we may eat foods that we don’t eat normally so it’s worth a reminder that some food/drinks can interact with certain medications.
Green leafy vegetables such as sprouts and broccoli contain high levels of vitamin k and this counteracts the effects of warfarin making it less effective. It's important that you eat foods containing vitamin K, so rather than leaving them out of your diet, make sure you eat similar amounts of them regularly. This will mean the level of vitamin K in your blood stays fairly constant and makes it more likely that your INR level stays stable.
Do not drink cranberry or grapefruit juice while you're taking warfarin. It can increase the effect of your medicine and put you at higher risk of bleeding.
Grapefruit contains substances called furanocoumarins, which selectively inhibit isoenzyme CYP3A4. Because this particular enzyme pathway is responsible for metabolising nearly 50% of all pharmaceuticals, this poses a huge potential for interactions. When mixed with grapefruit, certain medications such as antihypertensives, HIV medications, statins and immunosuppressants may have reduced metabolism, leading to possible drug toxicity.
When you get to the cheese board avoid mature or blue cheese as they also contain high levels of vitamin k which counteracts warfarins anti-coagulant effect.
It’s always a good idea to limit alcohol, but if you are taking drugs such antibiotics alcohol will react with them. High levels will also react with warfarin.
Chocolate and red wine contain an amino acid derivative called tyramine. F you are taking Monoamine oxidase inhibitors (antidepressants) including tranylcypromine, phenelzine and isocarboxazid you should avoid foods containing tyramine.
This is by no means a comprehensive list of all food/drink so if in doubt check with your pharmacist or check the patient information leaflet that comes in the box with the drugs as they usually will list anything to avoid.
Angie Davidson
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