Samarium (153Sm) lexidronam

Samarium (¹⁵³Sm) lexidronam (chemical name Samarium-153-ethylene diamine tetramethylene phosphonate, abbreviated Samarium-153 EDTMP, trade name Quadramet) is a chelated complex of a radioisotope of the element samarium with EDTMP. It is used to treat pain when cancer has spread to the bone.^[1][2]

Samarium (¹⁵³Sm) lexidronam

Clinical data
Trade names	Quadramet
Routes of administration	Intravenous
ATC code	V10BX02 (WHO)
Legal status
Legal status	EU: Rx-only In general: ℞ (Prescription only)
Pharmacokinetic data
Bioavailability	N/A
Identifiers
IUPAC name Pentasodium samarium (153Sm) N,N,N',N'-tetrakis(phosphonatomethyl)ethane-1,2-diamine
CAS Number	122575-21-7 Y 176669-18-4 (pentasodium)
PubChem CID	9810246
UNII	745X144DZY
ChEMBL	ChEMBL1201796
CompTox Dashboard (EPA)	DTXSID30936282
Chemical and physical data
Formula	C6H12N2Na5O12P4153Sm
Molar mass	695.93 g/mol
3D model (JSmol)	Interactive image covalent form: Interactive image
SMILES C(CN(CP(=O)([O-])[O-])CP(=O)([O-])[O-])N(CP(=O)([O-])[O-])CP(=O)([O-])[O-].[Na+].[Na+].[Na+].[Na+].[Na+].[153Sm+3] covalent form: C(CN(CP(=O)([O-])O[153Sm-]123)CP(=O)([O-])O1)N(CP(=O)([O-])O2)CP(=O)([O-])O3.[Na+].[Na+].[Na+].[Na+].[Na+]

It is injected into a vein and distributed throughout the body, where it is preferentially absorbed in areas where cancer has invaded the bone. The radioisotope ¹⁵³Sm, with a half-life of 46.3 hours, decays by emitting beta particles (electrons), which kill the nearby 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

Side effects^[3] include the following:

• Black, tarry stools
• Blood in urine/stool
• Cough, hoarseness
• Fever/chills
• Lower back/side pain
• Painful or difficult urination
• Pinpoint red spots on skin
• Irregular heartbeat
• Nausea, vomiting

Supply and administration

Samarium lexidronam is supplied as a frozen solution for intravenous use with an activity of 50±5 mCi/mL^[4] and a maximum beta energy of 0.808 MeV.^[5] Due to the short half-life of the radioisotope, the drug expires 56 hours after the noted calibration time.^[4]