Chemotherapy

Chemotherapy is drug treatment used to treat cancer. In chemotherapy, different chemotherapy drugs are used. Today, various chemotherapy drugs are available in market. Chemotherapy drugs are classified into different categories according to their chemical structure, their working and their relationship with other drug. Some drugs are grouped into one group because they are derived from same plant. Some drugs belong to more than one group. Classification of chemotherapy drugs is helpful for selection of better combination of drugs.
Following are the different types of chemotherapy drugs classified based on their chemical structures and the way act on cancer cells:

Alkylating agents

Alkylating agents were among the first chemotherapy drugs used to treat cancer. This type of chemotherapy drugs attack on DNA of cell which causes cross linking of DNA strand and stop or prevent replication of cancer cells. Now days, alkylating agents are the most commonly used agents in chemotherapy. Alkylating agents can be used for treat most types of cancer, however they are most effective in treating slow growing cancers rather than rapidly growing cancers. Chlorambucil, cyclophosphamide, thiotepa, and busulfan are the commonly used alkylating agents used as chemotherapy drugs.

Antimetabolites

Antimetabolites are another type of chemotherapy drugs. Antimetabolites replace natural substances in DNA molecules which alter the function of enzymes required for cell metabolism and protein synthesis. They stop nutrients from reaching the cell so eventually cells starve to death.
Antimetabolites are specific to cell cycle as they are most effective during the S-phase of cell division. In this phase, cells undergo synthesis of DNA formation of new cells. Antimetabolites attack cells which are growing and dividing rapidly. Antimetabolites drugs include purine antagonists, pyrimidine antagonists, and folate antagonists.

Plant alkaloids

Plant alkaloids are another type of anti-cancerous drugs. This type of chemotherapy drugs are derived from plants. They act on cancers cells and prevent them from dividing themselves. Some drugs of this type act throughout the cell cycle while others are cycle specific that is more effective during the S and M phases of cell. Plant alkaloids that are used in chemotherapy include actinomycin D, doxorubicin and mitomycin.

Antitumor antibiotic

Another type of chemotherapy drugs includes antitumor antibiotics. This type of antitumor antibiotics is not specific to cell cycle. Antitumor antibiotics drugs act on cells by binding with DNA and thus stopping RNA synthesis which create proteins which are necessary for cell survival. These drugs cause the strands of genetic material that make up DNA to uncoil which prevent the cell from reproducing. Some commonly used antitumor antibiotics for chemotherapy are doxorubicin, mitoxantrone and bleomycin.

Chemotherapy drugs are administered by different means including intravenously, intramuscular, orally, topically. Way of administration depends on the type of cancer and the type of chemotherapy drug used. Also, amount or dose of chemotherapy drug is also important as fewer doses are not effective while higher dose causes more side effects.

If you want to know more about the type of chemotherapies available, check the types of chamotherapies page.