They league themselves to the DNA in order to hinder the separation them its two filaments of the double helix to espiralar, phenomenon this indispensable one for the response (Control of the cancer, 2006). The alquilantes affect the cells in all the phases of the cellular cycle in not specific way. Although effective as isolated agents for innumerable forms of cancer, them rare they produce excellent clinical effect without the combination with other phase-specific agents of the cellular cycle. The main employed drugs of this category include the mustard nitrogenada, the mustard fenil-alanine, the ciclofosfamida one bussulfam, it, the nitrossurias, the cisplatina and its analogous carboplatina and the ifosfamida one (Control of the cancer, 2006). The antimetablitos affect the cells inhibiting biosynthesis of the essential components of the DNA and the RNA. In this way, they hinder the normal multiplication and the functioning of the cell. The inhibition of biosynthesis can be directed to the purinas (as is the action of quimioterpicos 6? mercaptopurina and 6-tiogunina), to the production of acid timidlico (5-fluoruracil and metrotexato) and to other stages of the synthesis of acid nuclicos (citosina? citarabina arabinasdeo C or) (Control of the cancer, 2006).
The antimetabolic ones are particularly active against cells that if find in the phase of synthesis of the cellular cycle (phase S). The duration of the life of the susceptible tumorais cells determines the average of destruction of these cells, which are hindered to enter in mitose for the action of the metabolic agents who act in phase S. As it can be deduced, the differences between kinetic the cellular one of each type of tumor can have considerable effect in the clinic, as much in the indication how much in the project of administration of these agents (Control of the cancer, 2006). The antibiotics are a group of substances with chemical structure varied that, even so they interact with the DNA and they inhibit the synthesis of this acid one or of proteins, they do not act specifically on one definitive phase of the cellular cycle.