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Do vitamin supplements react with methotrexate?

Q) I take plaquenil and methotrexate for my rheumatoid arthritis, and folic acid. My rheumatology clinic has suggested not taking vitamin supplements as it's not known if they'll react with methotrexate and stop it working. What do you think about supplements and methotrexate?
Joyce Almgill, York, Yorkshire (Spring 2010)

A) I presume your clinic was unsure which supplemental vitamins you were taking. From a prescriber’s point of view that's the nightmare – the patient taking a drug or drugs which they have bought themselves and which may interact or counteract with a drug that has been prescribed for their condition. I use the word ‘drug’ loosely, as many food supplements and vitamins can interact with prescribed medication. An example is grapefruit juice and ciclosporin – the one counteracts the other. In the case of methotrexate the concern would largely be folic and folinic acids, which act against the methotrexate. Folic acid is usually prescribed, in small doses, along with methotrexate so that it can minimise the side-effects of the drug. Large doses, particularly taken on the same day as methotrexate, would stop the drug working. Some foods also contain folic acid, particularly green vegetables such as broccoli, Brussels sprouts, asparagus and peas, as well as chickpeas and brown rice.

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