Cytotoxic Actions and Precautions

Cytotoxic Chemotherapy and Other Cytotoxic Agents

photo of IV system containing cytotoxic chemotherapy
What does cytotoxic mean?.

Cytotoxic refers to a substance or process which results in cell damage or cell death. The prefix "cyto" refers to cell and "toxic" to poison. the term is often used to describe chemotherapy drugs that kill cancer cells, but it may also be used to describe toxins, such as venom. Within our own immune systems we have cells that are considered cytotoxic, such as the T cells that kill bacteria, viruses, and cancer cells. The label "cytotoxic" is important for medical professionals who will be handling cytotoxic medications or other substances that can cause cell death, and specific precautions are necessary for safety.

Cytotoxic Drugs

Most of the time the term "cytotoxic" refers to the effect that a chemotherapy drug has on cancer cells. In this sense, a cytotoxic agent may be differentiated from one that is cytostatic. A cytostatic medication would, in contrast, inhibit cell division and growth but would not result in cell death directly.

Cytotoxic drugs work by interrupting cells at particular places in the growth cycle. They are most likely to affect cells that are growing rapidly, for example, cancer cells, hair follicles, bone marrow and cells lining the stomach and intestines. The reason that most chemotherapy uses a combination of drugs and that most chemotherapy cycles are repeated is because cells are in various places in the division process.

Not all drugs used to treat cancer are cytotoxic. Chemotherapy drugs are designed to kill all rapidly growing cells, including normal cells in the body that divide rapidly. Some of the newer types of cancer drugs, such as targeted therapies and immunotherapies, are not considered cytotoxic. These drugs work either to interfere with particular pathway in the growth of cancer cells, or to stimulate or use the immune system in some way to fight cancer. Some immunotherapies, such as CAR T, may be considered cytotoxic in a way, as they take advantage of the cytotoxic actions of the body's own cytotoxic T cells.

Cytotoxic Agents in Humans or Animals

There are other cytotoxic substances used for a wide array of functions. As with cytotoxic chemotherapy drugs, this simply means that they kill cells.

Cytotoxic T cells

Cytotoxic agents are not just created to destroy cancers and control diseases. Our bodies also manufacture cytotoxic T-cells (cytotoxic T lymphocytes). Cytotoxic T cells are part of the immune system, which searches for, finds and destroys cells infected by viruses as well as cancer cells.

One of the most rapidly advancing areas of cancer research is now focusing on harnessing and stimulating our own cytotoxic cells to fight cancer in our bodies. These treatments work in a number of different ways; some by allowing the T cells to "see" cancer cells that were previously hidden, others by harvesting and multiplying these cells, and more.

Cytotoxic Venom

Humans are not alone in their use of cytotoxic T cells. Some venoms, such as those emitted by vipers, cobras and violin spiders, are also cytotoxic.

Mechanism of Action

Cytotoxic agents can kill cells in several ways. They may harm the cell so that its cell membrane is weakened and the cell explodes (lysis) or they may interfere with cell division so the cell stops growing and dividing.

Terminology: Cytotoxic vs. Genotoxic vs. Mutagenic, etc.

The terminology can be very confusing when looking at drugs or other substances that damage cells or DNA in cells.

Cytotoxic vs Genotoxic

There is much confusion between the terms cytotoxic and genotoxic. The term cytotoxic refers to the ability of a substance to cause damage to cells. The term genotoxic refers to the ability of a substance to directly damage DNA in cells.


A few other definitions are important to explain when talking about cytotoxicity. The term carcinogenic refers to a cytotoxic substance has the ability to cause DNA damage that could ultimately lead to the development of cancer. In contrast, the term mutagenic refers to cytotoxic substances could potentially instead damage the chromosomes in a fetus.

This is why it is extremely important for people to practice caution when they are handling cytotoxic drugs and substances.

Dangers of Cytotoxic Drugs and Agents

Cytotoxic drugs can kill cancer cells but they can also damage normal, healthy cells as is evidence by the side effects of most chemotherapy drugs.

Cytotoxic Precautions

For those who work with cytotoxic medications or other substances, precautions are recommended specifically to avoid carcinogenicity and mutagenicity. The specific precautions will vary considerably based on the route of possible exposure but may include:

  • Gloves, with cuffs tucked under the gloves
  • Long sleeve clothing
  • Disposable gowns
  • Safety glasses
  • Respiratory protection

A Word From Verywell

The term "cytotoxic" can be frightening, especially if you see the label on something that will be injected into your body. But our own bodies make substances that are cytotoxic as well. It's important to understand how these substances, work, however, to protect yourself in the environment around us.

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