[5-fluorouracil in high doses. Principles and toxicity]

5 fluorouracil (5FU) is considered the most important chemotherapeutic agent for gastrointestinal cancer treatment. High dose 5FU (3 gr./m2), given together with allopurinol to prevent normal tissue toxicity may be used to get a better therapeutic index. Toxic effects are specially considered in this paper, where effects in 20 advanced gastrointestinal patients are evaluated. Taking into consideration the results obtained, we consider it can be safely used in this way.