Aspirin [2-(acetyloxy) benzoic acid] (Fig 1), acts as an inhibitor of cyclooxygenase which results in the inhibition of the biosynthesis of prostaglandins. It also inhibits platelet aggregation and is used in the prevention of arterial and venous thrombosis . 5-Fluorouracil (Fig 2) is a pyrimidine analogue that irreversibly inhibits thymidylate syntheses. Blocking the synthesis of thymidylate which is required for DNA synthesis. Intracellular metabolites of 5-Fluorouracil exert cytotoxic effects by either inhibiting thymidylate synthesis or through incorporation into RNA & DNA, ultimately initiating apoptosis . 5- Fluorouracil has been widely used to treat many gastrointestinal tract adenocarcinomas. Tegafur [4-Fluoro-1-(2- t e t r a h y d r o f u r y l ) – 2 , 4 ( 1 H , 3 H ) – pyrimidinedione] is a prodrug of 5- Fluorouracil (5-FU) and is converted into 5-FU by cytochrome P450 enzymes .