Biodistribution studies of the 186Re complex of 3-amino-1-hydroxypropylidene-1,1-bisphosphonic acid in mice.

Preliminary studies of 186 Re-labelled 3-amino-1-hydroxypropylidene-1,1-bisphosphonic acid (APD) were performed to determine its potential for bone pain palliation, and as a treatment for increased bone resorption. The synthesis of 186 Re-APD was carried out by reduction of 186 Re-perrhenate in the presence of SnCl 2 . The APD kit, comprising 2.5 mg of APD, 2.5 mg of gentisic acid and 1 mg of Sn ++ as SnCl 2 2H 2 O, was prepared in-house. The APD was labelled with 186 Re and injected intravenously into normal mice. Mice were subsequently sacrificed at 1, 3, 24, 48, 72, 168 and 240 h post-injection. The greatest accumulation of 186 Re-labelled APD was found in bone, resulting in bone-to-blood ratios of 25, 35, 65, 100, 151, 181 and 189, respectively. 186 Re-APD showed high uptake in bone, and relatively low uptake in soft tissue, suggesting that 186 Re-APD is a potential agent for bone therapy.