Fluorouracil (5-FU) is a commonly used anticancer drug. It functions by irreversibly inhibiting thymidylate synthase. 5-FU is widely used in a number of cancers worldwide. Detoxification of 5-FU is mediated by the dihydropyrimidine dehydrogenase (DPD) gene . Apart from 5-FU, the gene also is involved in detoxification of Capecitabine, and Tegafur. Genetic variations in the gene can cause a partial or complete deficiency of function, which may lead to drug toxicity, which is severe.