Preparation of 153Sm-citrate-HA for radioactive synovectomy of rheumatoid arthritis

A new kind of labelled radiopharmaceutical hydroxyapatite (HA) by means of transfer complexing for the treatment of rheumatoid arthritis is described. HA with partials of 2-10 μm is labelled with 153Sm by a citrate transfer ligand. 153Sm-citrate-HA is obtained in high yield and is extremely stable in vitro. The complexing capability of HA is about 5 mg Sm2O3/g HA, the decomposition rates of 153Sm-citrate-HA both in saline of 0.9% and in human plasma (37 +- 0.5 degree C) are less than 2.0% for a period of 3 half lives. Biodistribution studies in rabbits demonstrated long term retention of nearly 99% of injected 153Sm-Citrate-HA in arthritis joint. Extra-articular leakage of radioactivity in both blood and urine accounted for 0.5% of injected dose, and few retained in other major tissues after about 14.8 MBq of 153Sm-Citrate-HA has injected into the left knee joint of normal rabbits. 153Sm-citrate-HA could be potentially useful in radio-synovectomy treatment of rheumatism arthritis