Types of chemotherapy drugs: Which drugs are used in chemotherapy?

What are the different types of chemotherapy?

Chemotherapy drugs are classified by their structure and function. They fall mainly into the following five classifications:

• Alkylating agents are known for their chemical action, which interferes with cell division. They are called noncell cycle specific agents because they attack all cells in a tumor whether the cells are resting or dividing. They work by stopping or slowing down cell growth.

• Antimetabolites are drugs which interfere with the cells' ability to replicate. These drugs are designed to starve cancer cells by interfering with vital life processes. They fool the cell by introducing the wrong building elements or blocking synthesis of the right ones.

• Natural products include plant alkaloids and antibiotics. Plant alkaloids stop cell division at one of its phases. Antibiotics are made from molds like penicillin but are stronger and do not act in the same way as regular antibiotics. Rather, they interfere with cell division and damage more cancer cells than normal cells.

• Hormones are naturally occurring substances in the body that stimulate or turn off the growth or activity of specific cells or organs. In cancer treatment, the environment is changed either by adding or removing the hormones, thus antagonizing the growth stimulating hormones that promote growth of cancer cells in certain tissues.

• Miscellaneous agents which don't fit into any of the other categories.

Who prescribes chemotherapy? 

Chemotherapy should be prescribed by a doctor who has had special training in the use of drugs and drug combinations for the treatment of cancer. This may be a medical oncologist (chemotherapist), who is a specialist in internal medicine with special training in the overall care of the cancer patient, or a hematologist, who is a physician who specializes in blood diseases. Most chemotherapy drugs are too risky to be prescribed by general physicians without special training.

Do nurses play a role in actually administering the chemotherapeutic drugs? 

Absolutely. There are specially trained chemotherapy nurses in many parts of the country, both in doctors' offices and in hospitals (outpatient clinics and inpatient facilities), who actually give the majority of chemotherapeutic drugs under the supervision of a physician. These nurses are well trained in the administration of the drugs and know what side effects to look for.

Why is it important to have specially trained personnel dealing with chemotherapeutic drugs? 

Chemotherapy, and especially combination chemotherapy (in which more than one drug is used), may be a highly toxic form of cancer treatment. Patients who are not closely monitored could die from the side effects, because the drugs are very potent. In addition, it is a field of medicine that is new and changing quickly. New forms of therapy may not always reach the doctors who are not specializing in this field. If you are living in a community that does not have a specialist to administer the drugs, you should make sure your doctor seeks a consultation with a cancer center, a medical school, or a large medical center for guidance from experts who know the latest drugs in use, the administration technique, how to adjust doses, and what the side effects are on the normal cells.

Where are the drugs given? 

Chemotherapy can be given either in a doctor's office or in a hospital the latter either in an outpatient clinic or as a patient in the hospital. Most times oral drugs can be taken at home. Many times the first doses of the drugs are given in the hospital so that a trained health care team can give them and closely monitor your reactions to them. This is usually only a 1- or 2-day stay, with the remaining drugs given in the doctor's office or outpatient clinic. In other cases, the drugs are given in the doctor's office or outpatient clinic from the beginning. Occasionally, you may have to stay in the hospital when drugs have to be given intravenously for a long period of time.

What are ‘targeted’ cancer drugs?

How does the doctor decide on what kind of drug to use? 

The doctor must look at your general condition, the type of tumor you have, and the extent of its growth. He evaluates the responses of chemotherapy in similar patients and selects that kind of chemotherapy which is most likely to damage or kill the tumor. However, not enough is known yet about the effects ofthe anticancer drugs on various kinds of cancers and individual differences among patients to make this an exact science. Thus the medical oncologist cannot always specifically predict how the drug will affect the tumor of any given patient, although he can usually predict the amount of toxicity of the drug. It has been said that using chemotherapy is like trying to kill crabgrass without killing the whole lawn.

What is meant by combination chemotherapy? 

That is when more than one drug is being used for treatment. Most often two to five drugs are used in combination. These combinations are often used in an attempt to kill cells in different phases of their reproductive cycle and to delay or prevent resistance of the tumor to the drugs from occurring.

Does each patient get the same dose of the drug? 

No. The doses are based on many things, including body size. Some of the dosages are calculated in milligrams of drug per kilogram of body weight. Others are calculated in milligrams of drug per square meter of body surface area. More and more drugs are being based on surface area because the surface area changes less during the course of the treatment and thus allows a more constant amount of the drug to be given during therapy. When more than one drug is used in a combination treatment plan, the dose for each drug is usually lower than when it is used alone. What the doctor is trying to do for each person is to give him the "maximum tolerated dose" that is, the amount of the drug which will give the greatest anticancer effect with the least amount of damage to normal cells.

Understanding Different Cancer Treatments

Are there any new developments in chemotherapy drugs and how they are administered? 

The following techniques and developments are currently under early investigation:

• Attaching a drug to monoclonal antibodies that will find and kill cancer cells, leaving normal cells alone • Using implanted, refillable pumps to deliver anticancer drugs directly to organs

• Isolating cancer cells from a patient's tumor in the laboratory and testing different drugs against those cells before chemotherapy is begun on the patient. It is hoped that this will allow doctors to match drugs more closely with an individual's disease.

• Finding new drugs which have fewer or less drastic side effects than the present drugs

• Using biological drugs that is, those made by the body itself which may be less toxic than conventional chemotherapy.

Why is it that some of the drugs are given by intravenous injection while others are given in pill form? 

It is because chemotherapy drugs differ in many ways, and this affects the form in which they are given. Some drugs are not absorbed when given by mouth and have to be given by injection.


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