"5-FU binds to an enzyme inside of cancer cells called Thymidilate Synthetase, and then exerts its anti-cancer effect on the cells. In general, 5-FU is relatively well tolerated at standard doses However, an estimated 3-8% of patients have a genetic variation that leads to a deficiency of an enzyme called Dihydropyrimidine dehydrogenase (DPD) that is crucial for the metabolism and deactivation of 5-FU. Patients with this variation have severe toxic reactions that may be fatal with even small doses and often the very first dose of 5-FU."
I am not trying to scare anyone, but I think this is important enough to share with the her2support members who may be considering Xeloda or who have not had success with Xeloda. I understand the test for this deficiency is a blood test.
Apparently Xeloda and 5 FU need the above enzyme to work properly. If a person does not have enough of the DPD enzyme and takes Xeloda it may not work well or it may cause very toxic side effects.
I wonder how many oncologists test their patients for the deficiency when they are considering Xeloda or 5FU?
Xeloda and 5 FU Toxicity
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