Action and Uses

The five major types of antineoplastic agents may be used in combination or alone. There are often specific research protocols or rules that govern the use of these medications. It is important for the nurse to accurately report all reactions and adverse effects the patient might have so the action of the drug can be understood.

Alkylating agents are used to interfere with the normal process of cell division. They are some of the most widely used antineoplastic drugs. These drugs attach physically to deoxyribonucleic acid (DNA) in the tumor cell, a process called alkylation. As they do this, they change the structure of DNA in cancer cells and prevent it from functioning normally. There are different alkylating agents and they all attach to DNA in different ways. Working together, they are able to kill the cell or stop the production of new tumor cells. Although the alkylation occurs in the cancer cells, the killing action does not occur until the affected cell tries to divide.

This alkylating effect occurs in rapidly growing malignant cells, but it also occurs in some normal cells. Within the body, normal rapidly growing cells such as blood cells, white blood cells (WBCs) and epithelial cells lining the GI tract are also damaged. Thus as soon as the alkylating medications are given, red blood cells, WBCs, and platelets begin dying. These patients experience anemia and higher risk of infection. The death or damage to cells lining the GI tract produces nausea, vomiting, and diarrhea.

Specific antibiotic preparations are used, not for their antiinfective properties, but to delay or prevent cell division of the malignant cells. This action is caused by interference with DNA and ribonucleic acid synthesis. These antitumor antibiotics are obtained from bacteria and have the ability to kill cancer cells. These chemicals are more toxic than other antibiotics and their use is limited to use in treating very specific cancers.

Because the antitumor antibiotics interact with DNA in a way similar to the alkylating agents, their general actions and side effects are similar to those of the alkylating agents. However, all the antitumor antibiotics must be given intravenously or put directly into a cavity of the body using a catheter.

Antimetabolites disrupt normal cell functions by interfering with various metabolic functions of the cells and interrupt critical cell pathways in cells. Cells that are rapidly growing require large amounts of nutrients to build nucleic acids and proteins. These drugs resemble the essential building blocks of the cells but when the cancer cell attempts to use these chemicals as building blocks, the cancer cells slow their growth or die. This action is most effective in cells that are the most rapidly dividing—cancer cells, as well as normal hair and skin cells.

Some tumors may depend on male or female hormones, the chemicals produced by the sex glands. In patients who have these types of tumors, various hormones that counteract the effects of the hormones used by the tumors may be effective in treatment. The mechanism of action is unclear. Administering high doses of specific hormones or hormone antagonists can block the receptors in reproductive tissue tumors and slow tumor growth. An example is the use of tamoxifen to slow specific types of breast cancers that depend on estrogen for growth. Administration of the female hormone estrogen also slows the growth of prostate cancer.

In general, hormones and hormone antagonists produce few of the cytotoxic side effects seen with other antineoplastic drugs. However, as these medications may be given in high doses and for long periods, they may produce other unpleasant side effects. They rarely produce cures but may slow the growth of the cancer.

There are a variety of other primary plant extracts or alkaloids that are used as antineoplastics. These chemicals have been isolated from a number of plants, including common flowers and shrubs. Although these chemicals are structurally different, they all have the ability to stop cell division. As a group, they may be called mitotic inhibitors.

Taxoids and topoisomerase inhibitors are other groups of medications that have biologic properties helpful in treating cancer. They often have significant adverse effects.

Biologic response modifiers are relativity new immunologic drugs that do not kill tumor cells directly themselves, but instead stimulate the body’s immune system to help it fight the cancer. They may also be helpful in minimizing the toxic effects of other antineoplastics. Specifically, some drugs work to prevent anemia, stimulate platelet production, or help prevent severe thrombocytopenia. Thus the quality of life of these patients may be better when these drugs are given.

Drug Interactions

Most antineoplastic drugs interact with other medications the patient may be taking. It is very important to consult the manufacturer’s guidelines before starting treatment.

Nursing Implications and Patient Teaching