How do anti-Cancer drugs work?
There are more than 100 chemo drugs for treating cancer. These may be used as combinations with other drugs or in standalone form. Each drug differs from the other in terms of its chemical composition, method of administration and side effects. Chemotherapeutic drugs target cells at multiple phases of their multiplication. This is called cell cycle. Clinical oncologists or doctors who treat cancer medically, work with various drug combinations and apply various treatment protocols that are based on dosages to be given based according to the time of the cell phase.
These drugs, however, are unable to differentiate between malignant and benign cells and damage the latter also, leading to side effects such as acute nausea, weight & hair loss, fever, loose motions, muscular cramps and profuse sweating. However, auxiliary treatment has now been introduced to control and combat these side effects.
Classification of chemotherapeutic drugs
Chemotherapeutic drugs are classified according to their method of working, chemical structure and how they relate to other drugs. Some drugs have multiple functions and belong to more than one group. It, therefore, becomes important to know the ways in which a drug works so that its side effects can be predicted. This also helps oncologists to decide on which drug combinations will work well as also in which order and the amount of each drug to be administered.
Workings of Alkylating Agents:
For instance, alkylating agents prevent cell multiplication by causing damage to their DNA. These drugs work well in all phases of the cell cycle and are given to treat lung, ovarian and breast cancer, lymphoma, leukemia, multiple myeloma, Hodgkin’s disease and sarcoma. However, since DNA damage is caused by these drugs, the patient’s bone marrow may get affected and lead to red blood cell production getting adversely affected. This may lead to leukemia in rare cases, which again is “dose-dependent.” This implies that the risk is lower when smaller doses of alkylating agents are given and goes up proportionately with the rise in dose. Statistics show that the risks of leukemia happening after a patient is exposed to alkylating agents is highest about five to ten years after receiving treatment.
The most notable alkylating agents are: Altretamine, Busulfan, Carmustine, Chlorambucil, Cisplatin, Cyclophosphamide, Dacarbazine, Melphalan, Lomustine, Temozolomide, Oxalaplatin and Thiotepa.
Antimetabolites : These are another group of anti-cancer drugs that arrest RNA and DNA growth by substitution of the normal DNA and RNA building blocks. Antimetabolites damage cells during that phase when cellular chromosomes are replicated. These are commonly used for treating blood, breast, ovarian and intestinal tract cancers. The most commonly used antimetabolites are: 5-fluorouracil, Capecitabine, 6-mercaptopurine, Floxuridine, Cytarabine, Gemcitabine, Fludarabine, Methotrexate, Hydroxyurea and Pemetrexed.
Other categories: The other categories of chemotherapeutic drugs are anti-tumor antibiotics, Anthracyclines, Topoisomerase Inhibitors, Mitotic Inhibitors, Corticosteroids and Differentiating Agents. Each category of drugs has a separate method of working that ranges from altering the malignant cell’s internal DNA to prevent it from multiplying; interfering with enzymes that copy DNA during the cell cycle to separating DNA strands for copying to preventing cell division and prevention of chemo-induced nausea & vomiting as also acute allergic reactions.
In addition to these, targeted therapies are also done to more specifically attack cancer cells so that the cancer is kept under control or prevented from relapsing.