Chemotherapy is a drug which goal is to stop the proliferation of cancer cells. The drug can be administered intravenously through a catheter in the chest or taken in pills. Once in the blood, it affects the whole body. Regarding cellular exposure, the mechanism of action will differ based on the class of the drug. Most of the therapeutic classes of drugs work through DNA in the nucleus or in the cytoplasm.
Chemotherapy, acting at the DNA level, blocks replication (division) and / or prevents transcription of cells. Thus, most cytotoxic substances act. They work using different mechanisms: covalently binding to DNA (alkylating agents such as Cyclophosphamide or Temozolomide), “sticking” between two bases or causing breaks (topoisomerase inhibitors), inhibiting their synthesis (anti-metabolites). This effect belongs to methotrexate, 5-fluorouracil, analogues of the Pyrimides, Capecitabine.
Other types of chemotherapy affect microtubules (mitotic spindle) and block mitosis. They are also cytotoxic drugs. Taxanes (Paclitaxel, Docetaxel) prevent the depolymerization of tubulin. Thus, microtubules are strengthened and polymerized, which leads to cell death in the mitosis phase.
Cytotoxic drugs have side effects. Most often, they are a direct consequence of their effect on non-tumor cells, because the cellular changes they cause are not specific to cancer cells only. First of all, tissues whose cells are renewed are affected, such as bone marrow (anemia, thrombocytopenia, leukopenia and neutropenia) or the mucous membrane of the digestive tract (oral mucositis, ulcers, diarrhea).
Anticancer drugs may also cause vomiting, alopecia for certain molecules, such as taxanes, infertility, and various adverse effects typical for a class or a specific molecule (peripheral and cold neuropathy for oxaliplatin). There are drugs that are effective against nausea (Ondansetron, Aprepitant), vomiting, or to prevent neutropenia (granulocytic or leukocyte growth factor) or for the treatment of anemia.
Chemotherapy side effects may not appear if the clinic provides effective supportive biotherapy.
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