Chemotherapy Drugs

Chemotherapy Drugs

Also called: Cancer Drugs, Cancer Medications

Reviewed By:
Martin E. Liebling, M.D., FACP
Mark Oren, M.D., FACP


Chemotherapy drugs are among the most commonly prescribed treatments for cancer. These drugs target fast-dividing cancer cells in an attempt to destroy them. There are many different kinds of chemotherapy drugs, and often they are used in combination to more effectively combat disease.

A medical oncologist is a physician who specializes in diagnosing and treating tumors with drugs. This physician is often considered the patient’s “quarterback” on the cancer care team. The oncologist considers many factors in deciding which chemotherapy drugs are most appropriate in treating a patient’s cancer. It is important that patients receive the exact amount of a medication to properly treat their cancer. Too little of a chemotherapy drug will result in a decreased benefit, while too much can produce an increased chance of life-threatening side effects. Patients are closely monitored to ensure that they are getting the most effective treatment possible for their disease and that the side effects are held to a minimum.

Patients who use chemotherapy drugs may experience significant side effects from the treatment. These side effects must be weighed against the potential life-saving benefits of chemotherapy. While chemotherapy medications most often are administered at a medical facility, they sometimes are taken at home. Patients who use and store chemotherapy drugs at home must follow strict guidelines to ensure that the drugs do not present a danger to themselves or to others.

About chemotherapy drugs

Chemotherapy drugs treat cancer by disrupting the life cycle of cancer cells to destroy them and/or prevent them from growing or reproducing. Chemotherapy may be administered using a single drug, but more often it involves a combination of medications. Treatment with chemotherapy may be used before, after or concurrently with radiation therapy, surgery, biological therapy or bone marrow transplants. 

Treatments can be administered in various ways. The type of chemotherapy medication used will largely determine the form of administration. For example, oral medications are given in pill or liquid form to swallow and topical medications are applied to the skin as creams, lotions or patches.

Other methods of chemotherapy administration can be some form of injection, in which a needle and syringe are used. Injected medications can be placed under the skin (subcutaneous), into muscles (intramuscular), into a body cavity (intracavity) or directly into a cancerous area (intralesional). However, most injected medications are delivered intravenously, that is, directly into a vein. Several types of vascular access devices (VADs) are used for are intravenous drug delivery. These include:

  • Needle. Usually inserted into a vein in the hand or lower arm at the beginning of a treatment session, and removed at the end of the session.

  • Catheter. Consists of a thin, flexible tube inserted into a larger vein, usually in the chest, arm, spine, abdomen, pelvis or chest. There are several types of catheters, including those that thread up towards the heart (peripherally inserted central catheter, or PICC) and those with several openings (tunneled central venous catheter, or TCVC). They may be used for long-term chemotherapy to minimize the number of needle sticks a patient must endure. They also may be used to administer several drugs at one time, or to administer drugs known to cause damage to skin and muscle tissue when they leak outside the vein.

  • Port. In some cases, the catheter is attached to a small plastic or metal disc placed under the skin. This is called a port. External pumps or internal pumps (surgically implanted) are sometimes used to administer certain medications continuously.

Treatment sessions can be scheduled in a patient’s home, physician’s office, clinic, or at a hospital, either as an outpatient or as an inpatient.

In some cases, chemotherapy will be given in high doses to certain specific and restricted areas of the body. This is known as regional chemotherapy, and it is usually focused on the tumor-bearing area of the body. This allows for more of the medication to be concentrated in the cancerous region while minimizing side effects throughout the rest of the body. Examples of this type of chemotherapy include:

  • Intra-arterial (artery)
  • Intravesical (bladder)
  • Intrapleural (chest)
  • Intraperitoneal (abdomen)
  • Intrathecal (central nervous system, via spinal fluid)

Different chemotherapy drugs work in different ways and at different points in the cell cycle. Using a combination of drugs in treatment can both increase the effectiveness of anti-cancer treatment and help prevent a cancer developing resistance to a single drug and sometimes can help minimize the side effects. 

A medical oncologist (a physician who specializes in diagnosing and treating tumors) will decide which chemotherapy drugs to use based on several factors. These include:

  • Cancer type and stage (how far it has spread)

  • Patient’s age and health (including other diseases, such as liver or kidney diseases)

  • Anti-cancer treatments given in the patient’s past

  • Side effects associated with various anti-cancer medications

  • Drug interactions among various anti-cancer medications and any other medications being taken by the patient

In all cases, weighing these factors can give physicians a better picture of which medication is best for a patient. Physicians also have to rely on their own judgment and clinical experience for the most effective treatment. As a result, different physicians may come to different conclusions about the details of the best approach to therapy.

Unlike most over-the-counter drugs, chemotherapy drugs have a very narrow therapeutic index. This means that chemotherapy drugs are only safe when used within strict guidelines – taking too little of a drug will produce little or no benefit, while taking too much of the drug can trigger potentially life-threatening side effects. For this reason, physicians very carefully calculate and measure the amount of chemotherapy medication that is delivered to a patient.

Chemotherapy is designed using two factors: dosage levels and chemotherapy cycles.

Dosage levels

Dosages are usually measured in milligrams (mg), and appropriate levels may be based on a patient’s weight as expressed in kilograms (kg,1 kilogram equals 2.2 pounds). More often, the amount of a medication administered during an individual session is determined by a formula based on a patient’s body surface area (BSA). This is calculated based on a patient’s weight and height.

Chemotherapy session schedule

Chemotherapy sessions are scheduled at regular intervals known as cycles. Cycles are planned in a way that allows the drugs to effectively attack the cancer, while also providing time for normal cells to rest and recover from damage. However, the schedule used for specific patients with specific cancers varies greatly. Sessions may be held every other day or may be divided by weeks. In other cases, continuous administration over several consecutive days is the best approach. Each cancer and each cancer patient responds to chemotherapy drugs differently and different drugs may be used for different cancers. The sessions are adjusted according to the patient‘s recovery time and the tolerance for additional drugs. The characteristics of the drug(s) administered also affect the treatment schedule.

Types and differences of chemotherapy drugs

There are dozens of chemotherapy drugs available to patients. These powerful anti-cancer drugs work by disrupting various aspects of the life cycle of cancer cells. Most living tissues consist of cells that grow and split into two new cells that replace dead cells. This process of division takes place in a series of steps that make up a cell cycle. In each step, activity occurs that affects the components of the cell, such as proteins, ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). Chemotherapy drugs may affect cancer cells during one or several of these phases.

There are four major classes of chemotherapy drugs. Each of these classes targets cancer cells to prevent them from reproducing and spreading to other areas of the body. The four classes include:

  • Alkylating agents. This is the oldest class of anti-cancer drugs that work in all phases of the cell cycle. They block the replication of DNA in cancer cells by attacking the negatively charged sites of DNA, including oxygen, nitrogen, phosphorous and sulfur atoms. This stops the cellular activity, effectively killing the cell. Nitrosoureas are alkylating agents that interfere with enzymes that repair DNA in cancer cells that have been damaged. Nitrosoureas travel easily to the brain and are often used in treating brain tumors. Alkylating agents are administered either orally or intravenously.

  • Anti-metabolites. These drugs interfere with specific metabolic pathways and block enzymes necessary for the DNA and RNA of cancer cells to live and grow. These agents attack during the process of cell division. Anti-metabolites imitate normal cell nutrients and fool the cancer cells into consuming them. They are administered either orally or intravenously.

  • Anti-tumor antibiotics. These agents interfere with cancer-cell DNA by blocking certain enzymes and cell division (mitosis) and by changing the membranes that surround cells. Anti-tumor antibiotics either break up chromosomes or retard the synthesis of RNA that the cell needs to grow. These drugs work in all phases of the cell cycle and are administered intravenously. They are different from the antibiotics used to treat infections.

  • Mitotic inhibitors. These drugs are plant alkaloids and other compounds acquired from natural products. Mitotic inhibitors can halt cell division or hinder enzymes from making the proteins required for cell reproduction. They are administered intravenously.

In addition to these major categories of chemotherapy drugs, other drugs may be used in ways related to chemotherapy. They may include hormone (e.g., corticosteroids, sex hormones) or biological therapies (e.g., immunotherapy). 

Anti-cancer drugs are often used in combination to more effectively attack cancer cells. In some cases, multiple medications may be given concurrently. In other situations, drugs may be prescribed in a sequential or staggered approach. For example, a patient initially may be given a drug that works in all phases of the cell cycle to reduce the size of a tumor. This may cause remaining cells to divide, at which point the patient will receive another drug that attacks a cell during a specific stage of that cell’s cycle.

Potential side effects of chemotherapy drugs

Although chemotherapy medications can be a powerful tool in fighting cancer, they often come with multiple – and sometimes severe – side effects. As a result, physicians are very careful with the doses of these medicines to try to reduce the likelihood of side effects or damage to body organs. For this same reason, treatment with chemotherapy drugs is carefully monitored. The list of side effects is long and broad. 

Drug or other interactions with chemo drugs

Many drugs – especially drugs containing aspirin and vitamins – have significant interactions when used with chemotherapy drugs. They can affect chemotherapy in two ways:

  • Reducing the effectiveness of chemotherapy medications
  • Worsening certain side effects associated with chemotherapy

Physicians will obtain the following information about additional prescriptions, over-the-counter medications, nutritional supplements, vitamins or herbal medications in a patient’s medication regimen:

  • Name of drug
  • Dosage level and schedule
  • Reason for drug use
  • How long drug has been used
  • Physician or healthcare professional who prescribed the drug
  • Source of over-the-counter medications

Physicians can monitor most intravenous chemotherapy and its interactions closely. They may need to be more vigilant for patients taking chemotherapy orally to ensure that the patient understands the drug and its dosage. Some studies show that less oversight of oral chemotherapy regimens may be associated with more adverse reactions.

Safe handling of medications

Some patients will use and store chemotherapy drugs in their homes. Patients need to follow safe handling procedures with chemotherapy drugs because many are potentially dangerous chemicals that can be harmful if mishandled.

The National Institutes of Health (NIH) recommends the following guidelines for patients using chemotherapy drugs:

Handling medications

  • Wash hands before and after handling medications.
  • Wear latex gloves when handling medications injected into the veins or muscles. Some oral chemotherapy drugs also require patients to wear gloves when touching the medication. Torn or punctured gloves should not be used. Gloves should be disposed of in specially marked chemotherapy waste bags.
  • Plastic-backed absorbent pads should be placed under the work area when changing pump cassettes or tubing associated with treatments.
  • IV connections should be checked regularly to ensure they are secure.

Storing medications

  • Keep drugs out of the reach of children and pets.
  • Drugs that require refrigeration should not be placed near the freezer, and should be separated from foods (i.e., placing them in a crisper).

Medication spills

  • Accidental spills that measure less than a teaspoon should be cleaned immediately while wearing two pairs of latex gloves. The area should be wiped with a gauze pad and cleaned three times with soap and water.
  • Larger spills should be wiped up with a gauze pad and cleaned several times with soap and water. Clothing soiled with hazardous drugs should be removed immediately after cleaning and washed separately from other clothing in hot water. Never use bare hands to touch clothing or other materials (such as bed linens) that have come into contact with chemotherapy drugs. If a spill kit is provided with a medication, patients should follow instructions on the spill kit.

Caring for splashed skin

  • Medication splashed on skin may cause irritation. The skin should be washed and dried thoroughly with soap and water. Skin should be observed for a week, and any redness or irritation should be reported to a physician.
  • Medications splashed into the eyes require patients to flush the eyes with tap water for at least five minutes. Patients should then contact a physician immediately for any further treatment.

Disposal of body waste when using chemotherapy drugs

  • Patients can use the bathroom as they normally would, but should be extra careful about washing their hands with soap and water afterward.
  • Caregivers should use gloves when handling a chemotherapy patient’s blood, urine, stool or vomited material. They should thoroughly wash their hands with soap and water after the treatment. Caregivers also should wear gloves for two days after a patient has undergone a treatment session to protect the caregiver from any potential exposure.
  • The diapers of babies who are undergoing chemotherapy should be sealed in zip-lock plastic bags before disposal. This should be done for two days after a chemotherapy session.

Disposal of chemotherapy drugs and supplies

  • All supplies used for preparing or giving chemotherapy drugs should be placed in zip–lock bags. The bags should then be returned to the hospital for proper disposal.
  • Syringes and needles should be placed in a proper disposal container. Ideally, this should be a “sharps box” available from a pharmacy. However, any sealed, puncture-proof disposal container will work. Patients should check with their physician to learn the best method of disposal for these items.

Child use issues with chemotherapy drugs

Children’s bodies process drugs differently than adults and they may have different levels of sensitivity to the medications. As a result, children undergoing chemotherapy may require that dosage levels be adjusted accordingly.

Elderly use issues with chemotherapy drugs

Elderly people may have varying levels of sensitivity to chemotherapy drugs. Factors that can influence this sensitivity include:

  • Poor nutritional status and general physical condtion, including decreased tolerance to medications
  • Other medications, including those currently taken and those used in the past
  • Radiation therapy, either current or in the past
  • Low blood cell counts
  • Presence of other diseases that can be adversely affected by chemotherapy drugs, such as heart, liver or kidney diseases

In addition, few studies have been conducted on the effects of chemotherapy on elderly patients. Several recent retrospective studies have indicated that elderly patients may experience equal or better survival benefits from receiving chemotherapy as younger patients do.

Ongoing research

A great deal of research is devoted to the development of new chemotherapy drugs, drug combinations or delivery methods. The areas of research in chemotherapy and chemotherapy drugs include:

  • New drugs. More than a dozen new chemotherapy drugs are being tested in clinical trials and show promise for fighting some forms of cancer. A special government license supplies these to clinical trial investigators, who are testing their effectiveness and safety. Cancer patients should check with their physicians about possible clinical trials.  
  • Drug combinations. Some chemotherapy drugs are being paired up with monoclonal antibodies (proteins being manufactured in a laboratory). These proteins may help guide the chemotherapy drug directly to the targeted cancer. Other drugs are being tested with chemoprotective agents to reduce the side effects of some chemotherapy drugs.
  • Dosage. Researchers are investigating the use of lower doses of chemotherapy drugs in certain cancer patients. The method, known as metronomic chemotherapy, uses a smaller dose than normal on a steady schedule. This type of chemotherapy is being used in clinical trials for a variety of cancers. Other research studies are examining dose and schedule variations for more effective treatment of cancer with fewer side effects.
  • Delivery system. Researchers are examining drug delivery methods for chemotherapy drugs. Recent studies have discovered increased survival when chemotherapy drugs are placed directly in body cavities, such as the abdomen for ovarian cancer. In addition, scientists are developing other forms of delivery methods, such as chemotherapy drugs that are placed inside of liposomes (synthetic fat globules). Studies suggest that the liposome may help the drug selectively target cancer cells while lowering adverse side effects. Certain forms of this chemotherapy medicine are already in use.
  • Genetic tests. Genetic information may provide more information for physicians about which cancers will respond better to chemotherapy. Certain genes have been identified for particular cancers that may inhibit tumor growth or indicate a better response from chemotherapy. Such tests for some cases of lung cancer and breast cancer have been studied in clinical trials.

Questions for your doctor about cancer drugs

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about chemotherapy drugs:

  1. What chemotherapy drugs will be used in my treatment?
  2. How will the drugs be administered?
  3. Where will I receive my chemotherapy?
  4. What schedule will I follow?
  5. How long do you anticipate me needing chemotherapy?
  6. What are the likely side effects from these drugs?
  7. Do I have any restrictions while I am receiving this drug?
  8. Am I using any medications or supplements that may interfere with my chemotherapy?
  9. How will you monitor the drug during treatment?
  10. Is it likely that I will be changing chemotherapy drugs during treatment?
  11. Will I need to self-administer any of my drugs?
  12. What tests will I need to determine if the drug is effective?
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