Types of Chemotherapy Drugs
All chemotherapy drugs cause side effects, from minor to major adverse reactions. But not all of them are the same class (or chemical type). Different types of antineoplastic drugs (chemo drugs) are now used to kill cancer cells. These medications treat different types and stages of cancer by either shrinking, slowing or stop the growth of the tumor. Chemotherapy drugs tend to affect cell division or DNA synthesis and other cellular functions of the rapidly dividing cancer cells, which is the main reason healthy cells that reproduce rapidly (cells in the bone marrow, digestive tract, hair follicles, and others) tend to be affected by cancer treatment, leading to many side effects (see Chemotherapy Side Effects for more details).
As mentioned above, there are various classesof chemotherapydrugs. The following are some ofdifferent chemotherapy drug types – based on their chemical structure and the mechanism they use to attack cancer cells- used today in cancer treatment:
Alkylating Agents: This class of chemotherapy drugs works by attacking and interfering with DNA replication and [SCRIPT_s/cfm/dict] of rapidly growing cells (the main characteristic of cancerous cells ), thus preventing them from reproducing further. They are the first class of chemotherapy agents used.
Due to their attack on the DNA, they often cause long-term damage to the healthy bone marrow. Although rare, some alkylating agents can lead to acute leukemia when high doses are administered. Some common types of alkylating agents include:
- Alkyl sulfonate: busulfan
- Metal salts: carboplatin, cisplatin and Oxaliplatin
- Ethylenimines: thiotepa and altretamine (hexamethylmelamine)
- Hydrazines and Triazines: procarbazine, altretamine, dacarbazine and temozolomide
- Nitrogen mustards: mechlorethamine, chlorambucil, cyclophosphamide, ifosfamide and melphalan
- Nitrosoureas: streptozocin, carmustine and lomustine. (These drugs are common in treatment of brain cancers due to the fact they can cross the blood-brain barrier)
Plant Alkaloids and Terpenoids: As the name says it, this group of c hemotherapy drugs is derived from plants; that does not mean they are natural though. Their mode of action is simple; they work by targeting cells during different phases of division. These drugs block the microtubule function that is very important for cell division. Some common types of plant alkaloids are as follows:
- Taxanes: paclitaxel and docetaxel
- Podophyllotoxins: etoposide and tenisopide
- Camptothecan analog: irinotecan and topotecan
- Vinca alkaloids: vincristine, vinblastine and vinorelbine
These chemo drugsare made from products produced by species of the Streptomyces bacteria.
They are usually cell cycle specific that inhibit DNA/RNA synthesis during multiple phases of cell cycle. Some common types of antitumor antibiotics include:
- Anthracyclines: daunorubicin, doxorubicin, epirubicin, idarubicin and mitoxantrone
- Chromomycins: dactinomycin and plicamycin
- anthracenedioneor dioxoanthracene : Mitoxantrone
- Miscellaneous drugs: bleomycin, Mitomycin
Topoisomerase Inhibitors: these chemotherapy drugs interfere with the topoisomerase enzymes which help in separation of the DNA strands for further replication. The types of topoisomerase inhibitors used include:
- Topoisomerase I inhibitors: irinotecan and topotecan
- Topoisomerase II inhibitors: amsacrine, etoposide, etoposide phosphate and teniposide
Miscellaneous Chemotherapy Drugs: certain chemo drugs, however, act in different ways which makes it difficult to class them in a specific category; they are called miscellaneouschemotherapy drugs. Most common of them include:
- Ribonucleotide reductase inhibitor: hydroxyurea
- Retinoids: bexarotene, isotretinoin and tretinoin (ATRA)
- Adrenocortical steroid inhibitor: mitotane
- Antimicrotubule agent : estramustine
- Enzymes: asparaginase and pegaspargase.