EMA’s safety committee (PRAC) has recommended that patients should be tested for the lack of an enzyme called dihydropyrimidine dehydrogenase (DPD) before starting cancer treatment with medicines containing fluorouracil given by injection or infusion (drip) and the related medicines capecitabine and tegafur, which are converted to fluorouracil in the body.
As treatment for severe fungal infections with flucytosine (another medicine related to fluorouracil) should not be delayed, testing patients for DPD deficiency before they start treatment is not required.
No pre-treatment testing is needed for patients treated with topical fluorouracil (applied to the skin to treat various skin conditions).
Lack of a working DPD enzyme [1], which is needed to break down fluorouracil, causes fluorouracil to build up in the blood. This may lead to severe and life-threatening side effects such as neutropenia (low levels of neutrophils, a type of white blood cells needed to fight infection), neurotoxicity (damage to the body’s nervous system), severe diarrhoea and stomatitis (inflammation of the lining of the mouth).
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[1]Up to 8% of the Caucasian population have low levels of a working DPD enzyme, and up to 0.5% completely lack the enzyme.
