Types of Chemotherapy Drugs

            Chemotherapy is a treatment for cancer that kills cancer cells through a variety of mechanisms such as damaging the genetic material of the cells or interfering with the growth and division of the cells.[1] Based on these different modes of action, there are several broad categories of chemotherapy drugs. These include alkylating agents, plant alkaloids (which includes topoisomerase inhibitors and mitotic inhibitors), anti-metabolites, anti-tumor antibiotics, corticosteroids, and miscellaneous other drugs.[2]

            Alkylating agents are the most common type of chemotherapy. They function by damaging the DNA in cancer cells and stopping their division. While alkylating agents can be used to treat most types of cancer, they are best at treating slow-growing cancers. Some examples include breast cancer, ovarian cancer, lung cancer, multiple myeloma sarcoma, and Hodgkin’s disease. High doses of alkylating agents can damage bone marrow, leading to another cancer called leukemia. Some common side effects of these drugs are low blood cell counts, anemia (due to low red blood cell levels), hair loss, intestinal damage, cessation of menstruation, and impaired sperm production. Some drugs in the alkylating agents class are chlorambucil, cyclophosphamide, thiotepa, and busulfan.[2]

            Plant alkaloids are derived from plants that possess anti-tumor qualities. Topoisomerase inhibitors block proteins called topoisomerases to stop cancer cells from dividing. Topoisomerase inhibitors are generally used to treat ovarian cancer, lung cancer, pancreatic cancer, gastrointestinal cancer, and leukemia. This category can be further divided into topoisomerase I and topoisomerase II inhibitors. Topoisomerase II inhibitors may increase the risk of developing another cancer. Other possible side effects of topoisomerase inhibitors are low blood cell counts, anemia, increased risk of infection (due to low white blood cell levels), increased risk of bruising and bleeding (due to low platelet levels), nausea, and diarrhea. Some drugs in the topoisomerase inhibitors category are irinotecan, topotecan, and teniposide.[2]

            Mitotic inhibitors prevent cancer cells from dividing by blocking the process of mitosis (cell division).[3] Mitotic inhibitors are typically used to treat breast cancer, lung cancer, myeloma, lymphoma, and leukemia. High doses of mitotic inhibitors may cause nerve damage. Some other possible side effects are vomiting, lack of appetite, abdominal pain, constipation, back pain, and weakness. Some examples of mitotic inhibitors include cabazitaxel, docetaxel, and vinorelbine.[2]

            Anti-metabolites affect the creation of DNA in cancer cells by taking the place of the metabolites that would normally be used. The cancer cells are then unable to make any new DNA and therefore cannot continue dividing.[4] Anti-metabolites are usually used to treat breast cancer, ovarian cancer, gastrointestinal cancer, and leukemia. Side effects of anti-metabolites may include increased risk of infection, nausea, vomiting, loss of appetite, ulcers, fatigue, fever, hair loss, liver damage, kidney failure, and pancreatitis (inflammation of the pancreas). Drugs in the anti-metabolites class include azacitidine, clofarabine, and floxuridine.[2]

            Anti-tumor antibiotics prevent the DNA in cancer cells from making copies by uncoiling DNA strands. These drugs are often used to treat ovarian cancer, lung cancer, prostate cancer, and colorectal cancer. High doses of anti-tumor antibiotics can cause heart damage, so there is often a lifetime limit of how long these drugs can be given. Some common side effects of anti-tumor antibiotics include low blood cell counts, fatigue, poor appetite, and mouth sores. Some examples of anti-tumor antibiotics are doxorubicin, bleomycin, and mitoxantrone.[2]

Corticosteroids are drugs that mimic the hormone cortisol in the body. Increasing cortisol levels in the body suppresses the immune system, thereby reducing inflammation.[5] Corticosteroids may be used to either treat cancer or prevent certain side effects of chemotherapy such as gastric problems or allergic reactions. Some side effects of corticosteroids are weight gain, increased appetite, mood changes, high blood pressure, trouble sleeping, and upset stomach.[2]

Some miscellaneous chemotherapy drugs that do not fall into any of the previously mentioned categories include hydroxyurea, mitotane, pegaspargase, estramustine, and bexarotene.[2]

References

1.     Common Types of Chemotherapy for Breast Cancer https://www.healthline.com/health/common-types-chemotherapy-breast-cancer (accessed May 27, 2021).

2.     Chemotherapy Types and the Cancers They’re Used For https://www.healthline.com/health/cancer/chemotherapy-types (accessed Jun 15, 2021).

3.     Mitotic inhibitors https://www.drugs.com/drug-class/mitotic-inhibitors.html (accessed Jun 16, 2021).

4.     Antimetabolites for Cancer: Effects, Benefits, Risks https://www.webmd.com/cancer/antimetabolite-medications-overview (accessed Jun 16, 2021).

5.     What to know about corticosteroids https://www.medicalnewstoday.com/articles/corticosteroids#how-they-work (accessed Jun 16, 2021).