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Resistance to chemotherapy reduces the effectiveness of many anti-cancer drugs. Since many tumours show a steep dose response curve to chemotherapeutics, it is possible to overcome this resistance by increasing the dose of the drug. However, this in turn poses another problem as toxicity to the drug develops. If the toxic effects can be either reduced or eliminated, it is possible to increase the dose of the drugs used to treat cancer. Investigators have explored such possibilities.

Given below are data from an investigation designed to test the abilities of a new drug to reduce the toxicity of a standard anti-cancer drug, MTX. Two groups of mice were used in the study. Both groups were injected with a single intraperitoneal dose (LD50) of MTX. The treatment group received in addition, the new drug, (twice daily by the same route). The investigators charted the survival of both groups over a 30 day period (see Fig below).


This problem was given as a final evaluation in the Introductory Pharmacology course. Students had not done cancer chemotherapy as part of the course, but that was not the issue at hand. They were asked to deal with the issue of toxicity. The majority of the students performed well and had many interesting explanations. However, some students misread the problem and did not realise that the mice used were not tumour-bearing ones. The addition of the single word "normal" would have avoided that difficulty. Unfortunately I failed to spot that until I saw the answers.

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