<P> Chemotherapy drugs are also used in conditioning regimens prior to bone marow transplant (hematopoietic stem cell transplant). Conditioning regimens are used to suppress the recipient's immune system in order to allow a transplant to engraft . Cyclophosphamide is a common cytotoxic drug used in this manner, and is often used in conjunction with total body irradiation . Chemotherapeutic drugs may be used at high doses to permanently remove the recipient's bone marrow cells (myeloablative conditioning) or at lower doses that will prevent permanent bone marrow loss (non-myeloablative and reduced intensity conditioning). When used in non-cancer setting, the treatment is still called "chemotherapy", and is often done in the same treatment centers used for people with cancer . </P> <P> Healthcare workers exposed to antineoplastic agents take precautions to keep their exposure to a minimum . There is a limitation in cytotoxics dissolution in Australia and the United States to 20 dissolutions per pharmacist / nurse, since pharmacists who prepare these drugs or nurses who may prepare or administer them are the two occupational groups with the highest potential exposure to antineoplastic agents . In addition, physicians and operating room personnel may also be exposed as they treat people . Hospital staff, such as shipping and receiving personnel, custodial workers, laundry workers, and waste handlers, all have potential exposure to these drugs during the course of their work . The increased use of antineoplastic agents in veterinary oncology also puts these workers at risk for exposure to these drugs . Routes of entry into the worker's body are skin absorption, inhalation, and ingestion via hand - to - mouth . The long - term effects of exposure include chromosomal abnormalities and infertility . </P> <P> There is an extensive list of antineoplastic agents . Several classification schemes have been used to subdivide the medicines used for cancer into several different types . </P> <P> The first use of small - molecule drugs to treat cancer was in the early 20th century, although the specific chemicals first used were not originally intended for that purpose . Mustard gas was used as a chemical warfare agent during World War I and was discovered to be a potent suppressor of hematopoiesis (blood production). A similar family of compounds known as nitrogen mustards were studied further during World War II at the Yale School of Medicine . It was reasoned that an agent that damaged the rapidly growing white blood cells might have a similar effect on cancer . Therefore, in December 1942, several people with advanced lymphomas (cancers of the lymphatic system and lymph nodes) were given the drug by vein, rather than by breathing the irritating gas . Their improvement, although temporary, was remarkable . Concurrently, during a military operation in World War II, following a German air raid on the Italian harbour of Bari, several hundred people were accidentally exposed to mustard gas, which had been transported there by the Allied forces to prepare for possible retaliation in the event of German use of chemical warfare . The survivors were later found to have very low white blood cell counts . After WWII was over and the reports declassified, the experiences converged and led researchers to look for other substances that might have similar effects against cancer . The first chemotherapy drug to be developed from this line of research was mustine . Since then, many other drugs have been developed to treat cancer, and drug development has exploded into a multibillion - dollar industry, although the principles and limitations of chemotherapy discovered by the early researchers still apply . </P>

What type of drug is used to inhibit the growth of malignant cells