Preparation, stability studies and pharmacological behavior of [186Re]Re–HEDP

99mTc–HEDP is widely used as a bone imaging agent and its Re analog [186Re]Re–HEDP is now well established as a therapeutic radiopharmaceutical for palliation of pain due to bone metastases. In the present paper, we report the work carried out for the preparation of stable 186Re–HEDP which retains RC purity up to 5 days when stored at 4°C. 186Re was prepared by irradiation of natural Re metal at a flux of 3×1013 neutrons/cm2/s for seven days and processed after a cooling period of four days. The specific activity of 186Re formed was not, vert, similar35 mCi/mg. A complex with RC purity >98% could be prepared by varying the reaction conditions. By carefully optimizing the reaction and storage conditions, a complex which was stable for over 4 days could be synthesized. Bio-distribution studies carried out in rats revealed not, vert, similar30% bone uptake of 186Re–HEDP at 3 h postinjection which remained almost constant for 48 h, at which time there was negligible activity in other organs.