The term chemotherapy was coined by Ehrlich himself at the beginning of the 20th century to describe the use of synthetic chemicals to destroy infective pathogens. The word 'chemotherapy' comes from two words: Chemical & Therapy. The term is originally used to describe the use of drugs that are ‘selectively toxic’ to invading microorganisms while having minimal effects on the host. It also refers to the use of drugs to treat tumours, and in the public mind at least, ‘chemotherapy’ is usually associated with cytotoxic anticancer drugs that cause unwanted effects such as loss of hair, nausea and vomiting. In cancer treatment, the term chemotherapy means treatment with cell killing (cytotoxic) drugs. One chemotherapy drug may be administered or a combination of different chemotherapy drugs. There are more than 60 different drugs currently available and new ones are being developed all the time. There are other types of cancer medicines or drugs that are not classify as chemotherapy. Some newer types of cancer drugs kill cancer cells but they work in a different way to chemotherapy. Drugs such as interferon and monoclonal antibodies like trastuzumab (Herceptin) and rituximab help to kill cancer. But they were developed from substances found naturally in the human immune system and they tend to be called immunotherapy or biological therapy or targetted therapy. Sometimes chemotherapy may be given alongside other types of cancer therapy, such as biological therapy.