Chemotherapy drugs are chemical agents that work by destroying fast-growing cells in the body. They are in a class of medications known as cytotoxic agents. Chemotherapy is typically used to treat cancer, since cancer cells grow and divide more quickly than other cells.

There are many different types of chemotherapy drugs. Each type can be classified by how the drug interrupts the stages of the cell cycle or the pathways involved in cell growth and division.

Chemotherapy aims to lower the total number of cancer cells in your body and reduce the likelihood that the cancer spreads to other parts of the body.

However, in addition to attacking cancer cells, chemotherapy can also attack some of the normal cells in your body. This can cause serious side effects that can negatively affect your quality of life.

If your doctor recommends chemotherapy to treat your cancer, it’s important that you talk with your doctor to help weigh the side effects against the risks of not treating your cancer with chemotherapy.

The Food and Drug Administration (FDA) has approved at least 61 cytotoxic drugs for cancer to date. These drugs can be broadly classified based on their mode of action (the way they work in the cell).

They may be classified by which activity or process in the cell they interfere with, or which part of the cell cycle they affect.

Chemotherapy often affects the DNA or RNA inside the cancer cell. DNA controls genetic information, while RNA helps send information from the DNA to proteins that control how the cell functions. Interrupting these cell processes causes the cancer cell to die (apoptosis).

The main categories of chemotherapy drugs include:

Alkylating agents

Alkylating agents work by directly damaging DNA and preventing cell division. Some examples of alkylating agents include:

Alkylating agents are used for most types of cancer but are thought to have the greatest value in treating slow-growing cancers.


Antimetabolites work by mimicking natural substances that the cell needs for normal functioning of RNA and DNA. They trick a cancer cell into using them over normal metabolites. The cell is unable to replicate and dies.

Some examples of antimetabolites are:

  • 5-fluorouracil (5-FU)
  • cytarabine
  • gemcitabine
  • methotrexate
  • fludarabine

Antimetabolites can also be used to treat a wide variety of cancer types, including:

Antitumor antibiotics

Antitumor antibiotics work differently than the antibiotics that are used to treat infections. Antitumor antibiotics either work by breaking up DNA strands or by slowing down or stopping DNA production and preventing RNA production.

Examples of antitumor antibiotics are:

  • bleomycin
  • doxorubicin
  • mitoxantrone

Antitumor antibiotics may be used to treat mainly solid cancers such as:

Plant alkaloids

Plant alkaloids are a group of chemotherapy drugs made from plants. For example, a chemotherapy drug known as vincristine is made from the leaves of a periwinkle plant, Vinca rosea.

Plant alkaloids can be further divided based on how they work.

Mitotic inhibitors work by blocking mitosis, or cell division. More specifically, they disrupt microtubules — structures that pull the cell apart when dividing.

Topoisomerase inhibitors interrupt DNA replication by blocking the action of essential enzymes known as topoisomerases. Topoisomerases are involved in the coiling of DNA.

Examples of plant alkaloids include:

  • vincristine
  • paclitaxel
  • docetaxel
  • topotecan

Plant alkaloids like docetaxel and paclitaxel are widely used in cancer treatment. They may treat a variety of cancers, including:

Chemotherapy can have many benefits. Chemotherapy may be used to:

  • cure cancer
  • keep cancer from spreading
  • slow cancer growth
  • shrink a tumor so it’s easier to be surgically removed (this is called neoadjuvant chemotherapy)
  • reduce the size of tumors that are causing pain or pressure somewhere in the body, such as the spine or other organs
  • destroy cancer cells that remain after surgery or radiation (this is called adjuvant chemotherapy)
  • improve outcomes from radiation or immunotherapy treatments

Though chemotherapy mainly acts on rapidly dividing cancer cells, it can also damage or kill other cells in the body, especially:

  • blood cells
  • skin cells
  • hair cells
  • the cells lining the intestine and mouth

The most common side effects of chemotherapy include:

Chemotherapy can also cause long-term side effects, including damage to the:

  • heart
  • kidneys
  • lungs
  • nerves
  • reproductive organs

Chemotherapy is often used in combination with other therapies, such as surgery, radiation, or hormone therapy.

However, sometimes a doctor will decide to forgo chemotherapy in favor of a different type of treatment altogether. This will depend on many factors, including:

  • your overall health
  • the type of cancer you have
  • the stage of cancer
  • previous treatments you’ve had

Examples of alternative cancer treatments include:

  • Hormone therapy. Hormone therapy works by slowing the production of hormones that feed tumors. It’s often used to treat hormone receptor-positive cancers, such as certain types of breast cancers.
  • Targeted therapy. This is a type of treatment directed at specific mutations or abnormalities in the tumor. Targeted therapies aim to specifically kill cancer cells without harming healthy cells.
  • Immunotherapy. Immunotherapy helps your immune system fight off the cancer cells.
  • Radiation therapy. Radiation therapy uses high-energy X-rays to kill cancer cells. It can target a specific tumor or organ.

How is chemotherapy delivered?

Chemotherapy is often given by intravenous (IV) injection, meaning that a needle is inserted directly into a vein. The medication can also be injected into a muscle (intramuscular injection) or under the skin (subcutaneous injection).

Over time, it can be painful to be repeatedly pricked with IV lines. In this case, your doctor may recommend a chemotherapy port to make it easier to receive chemotherapy agents.

A chemotherapy port is a small disc that’s inserted under the skin, usually just below the collarbone. Attached to the disc is a flexible tube called a line or catheter, which is inserted directly into a large vein. Chemotherapy drugs can then be given directly through the port.

Some chemotherapy drugs come in the form of oral pills that you swallow. Others are applied topically to the skin as a cream or ointment.

Is chemotherapy painful?

Most people experience no pain while their chemotherapy is being delivered.

After it’s given, chemotherapy can cause painful side effects such as numbness, tingling, or shooting pains in the hands and feet. This is called neuropathic pain. Chemotherapy can also cause:

  • mouth sores
  • headaches
  • joint pain
  • stomach pain

Speak with your doctor or care team about how to manage pain during chemotherapy treatment.

How can I manage the side effects of chemotherapy?

Treatment aimed at managing side effects and improving quality of life is known as palliative care.

Here are a few examples of palliative care for managing the side effects of chemotherapy:

Though you may experience nausea and vomiting while taking chemotherapy, it’s important to eat when you can to avoid becoming malnourished.

Chemotherapy drugs are one of several treatment options for cancer. These types of drugs work by destroying rapidly dividing cancer cells.

Chemotherapy agents can be further classified into different types depending on how they interrupt important cell processes and lead to cell death.

Your doctor may recommend a single chemotherapy drug or a combination of chemotherapy treatments.

Chemotherapy can be very effective, depending on the type of cancer you have and the stage, but it can also cause serious side effects.

Before deciding to have chemotherapy, try to learn as much as you can about the recommended treatment. Meet with your doctor to weigh the benefits of chemotherapy along with the potential risks and side effects.