Though there are hundreds of different drugs used for chemotherapy, they all fall within a few common categories. Alkylating agents and topoisomerase inhibitors attack the DNA of cancer cells, stopping them from reproducing and slowing tumor growth. Antimetabolites block the cancer cells' ability to use food for energy and to synthesize DNA. Cell division can be stopped with the use of vinca alkaloids. Cytotoxic antibiotics, also known as anthracyclines, disrupt RNA synthesis and DNA reproduction in the cells.
Some of the main types of chemotherapy chemicals are alkylating agents, including the class of drugs known as nitrosoureas. These drugs work by damaging DNA in the cancer cells, particularly during the synthesis phase, so that they are unable to replicate and spread. They can be given to patients intravenously or in some cases may be taken orally. Drugs in this category include cyclophosphamide, cisplatin, and mechlorethamine.
Topoisomerase inhibitors are another variety of chemical often used in chemotherapy. Like alkalyting agents, they damage the DNA of the cancer cells, destroying their ability to reproduce. The main difference is that topoisomerase inhibitors work while the cell is reproducing instead of after. Taxol and topotecan are drugs of this type, which are mainly administered intravenously.
Antimetabolites are another type of chemical often used in the treatment of several types of cancer. They mimic purines, a substance needed to create DNA during the synthesis phase of cell reproduction. This stops the cancer cells from developing normally, making them unable to reproduce. They also inhibit the ability of the cancer cells to use nutrients to make energy. 6-mercaptopurine and 5-fluorouracil are examples of this type of chemotherapy drug, which can be taken orally or given by IV.
Another group of commonly used chemotherapy chemicals are plant alkaloids, particularly those known as vinca alkaloids. These substances act on the cancer cells during their metaphase by binding to proteins needed for successful cell division. Typically given through an IV, these drugs include vincristine and vinblastine.
Anthracyclines, which are anti-tumor antibiotics, can also be used during chemotherapy treatment for a variety of cancers. They work by blocking RNA synthesis and keeping DNA strands from re-attaching to each other, destroying the cancer's ability to grow and reproduce. Chemicals in this category include mitoxantrone, doxorubicin and daunorubicin. These drugs are generally given intravenously, as they can have harmful effects on tissues other than the blood.