Chemotherapy refers to the use of drugs to destroy tumor cells, usually by destroying the ability of tumor cells to grow and divide. Chemotherapy is administered by a medical oncologist, who is a medical oncologist who specializes in applying drugs to treat tumors. A chemotherapy regimen usually consists of a specific course of treatment given over a period of time. Patients may be treated with one drug or a combination of other drugs at the same time. Chemotherapy is the application of drugs to treat tumors and may be given with one or in combination with multiple drugs. Systemic chemotherapy regimens reach tumor cells throughout the body through the blood system. Chemotherapy is administered either through an intravenous catheter, which is placed into a vein through a puncture needle, or through oral tablets or capsules (via the mouth). Chemotherapy may be administered preoperatively to reduce the size of the tumor or postoperatively to destroy any remaining tumor cells. Chemotherapy can also be combined with radiation therapy. The commonly recommended chemotherapy drugs are gemcitabine, fluorouracil and cisplatin. The side effects of chemotherapy vary according to the individual and the dose, but all include weakness, risk of infection, nausea, vomiting, hair loss, loss of appetite, and diarrhea. These side effects usually disappear as soon as treatment ends. Chemotherapy is one of the palliative treatment modalities for gallbladder cancer. Chemotherapy may be administered preoperatively to reduce the size of the tumor or postoperatively to destroy any remaining tumor cells.