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Methotrexate (Anti-Rheumatic) oral

Methotrexate; Pralatrexate/Sulfonamides; Trimethoprim

This information is generalized and not intended as specific medical advice. Consult your healthcare professional before taking or discontinuing any drug or commencing any course of treatment.

Medical warning:

Serious. These medicines may interact and cause very harmful effects. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.

How the interaction occurs:

When these two medicines are taken together, your body may not process methotrexate or pralatrexate properly.

What might happen:

Your blood levels of methotrexate or pralatrexate may increase and cause easy bruising or bleeding, persistent sore throat or fever, or fatigue. These effects are more likely if you are taking a high dose of methotrexate, such as those used in the treatment of cancer or psoriasis.

What you should do about this interaction:

Contact your healthcare professionals (e.g. doctor or pharmacist) about taking these two medicines together. They may already be aware of this interaction and may be monitoring you for it. If you experience swelling or soreness of the mouth or tongue, easy bruising or bleeding, persistent sore mouth or fever, or unusual fatigue, contact your doctor. Do not start, stop, or change the dosage of any medicine before checking with them first.


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13.Haagsma CJ, van Riel PL, de Rooij DJ, Vree TB, Russel FJ, van't Hof MA, van de Putte LB. Combination of methotrexate and sulphasalazine vs methotrexate alone: a randomized open clinical trial in rheumatoid arthritis patients resistant to sulphasalazine therapy. Br J Rheumatol 1994 Nov;33(11):1049-55.
14.Ferrazzini G, Klein J, Sulh H, Chung D, Griesbrecht E, Koren G. Interaction between trimethoprim-sulfamethoxazole and methotrexate in children with leukemia. J Pediatr 1990 Nov;117(5):823-6.
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