Samarium (153Sm) lexidronam (chemical name Samarium-153-ethylene diamine tetramethylene phosphonate, abbreviated Samarium-153 EDTMP, trade name Quadramet) is a complex of a radioisotope of the lanthanide element samarium with the chelator EDTMP. It is used to treat pain when cancer has spread to the bone.
It is injected into a vein and distributed throughout the body. It is preferentially absorbed in areas where cancer has invaded the bone. There the radioisotope emits beta particles (electrons) which kill the nearby cancer cells. Pain begins to improve in the first week for most people and the effects can last several months. It is commonly used in lung cancer, prostate cancer, breast cancer, and osteosarcoma.
Side effects result from radiation to the bone marrow and include thrombocytopenia and leukopenia.