ABSTRACT
The design of a combination drug protocol must take into account the toxicology and pharmacology of the individual agents and the extent to which they interact with each other, both at the cellular biochemical level and their kinetic effects on normal and neoplastic tissues. Instances where a tumor recurs while undergoing continuous treatment with the same drugs that initially produced response can be more unambiguously attributed to the selection of specifically drug resistant cells. One of the initial objections to combination chemotherapy was the criticism that if one used a combination of drugs and it proved to be beneficial then one would not be in the position of knowing which of the drugs in the combination had been the effective agent. Much of the improvement in end results seen in clinical cancer chemotherapy has come about because of the introduction of effective combination chemotherapy protocols into practice.
