Chemotherapy refers to drugs that are used to kill microorganisms (bacteria, viruses, fungi) and cancer cells. Most commonly, the term is used to refer to cancer-fighting drugs.

Chemotherapy, as it refers to cancer treatment, is a generic term and includes many different drugs with a wide variety and severity of side effects. Generalizations regarding specific side effects and toxicities are difficult to make.

Cancer chemotherapy kills or arrests the growth of cancer cells by targeting specific parts of the cell growth cycle. However, normal healthy cells share some of these pathways, and thus are also injured or killed by chemotherapy. This is what causes most side effects from chemotherapy.

Chemotherapy usually targets rapidly dividing cells. Some normal cells -- including blood cells, hair, and cells lining the gastrointestinal tract -- are also rapidly dividing. These are the normal cells most likely to be damaged.

Newer cancer therapies, some of which have already been approved by the FDA, are more specifically targeted at growth pathways that are only found in cancer cells. These drugs may be more effective while also being less toxic.