Preparation and evaluation of a lyophilised kit for the preparation of ^99mTc-alendronate

4-amino-1-hydroxy butylidene biphosphonic acid (alendronate) is used for the treatment of osteitis deformans, postmenopausal osteoporosis, and hypercalcemia related to malignancy. As a part of the on going product development work of our programme, BRIT has undertaken the development work on preparation of a lyophilised kit of 99mTc-alendronate and studied its utility as a bone scintigraphy agent. The 99mTc-Alendronate complex showed good RC purity and excellent pharmacokinetics as indicated by the faster blood clearance, lesser in-vivo degradation leading to better contrast images.

A lyophilised kit having composition of alendronate, gentisic acid, stannous chloride dihydrate, sodium chloride was prepared and evaluated with respect to its radiochemical purity and biodistribution.

The Radiolabeling was done by the addition of sodium pertechnetate solution to the lyophilized kit vial. The radiochemical purity was assessed by paper chromatography using two solvent systems namely 85% methanol and 0.5 M acetate buffer. RC purity was found to be >95% and the complex formed is stable upto 6 h. Further stability studies are going on. Intial bio-distribution studies in Wistar rats showed excellent uptake and retention in femurs at 1 hr post injection. The results are comparable with the currently used bone imaging agent - ^99mTc-MDP. Imaging studies are planned in the larger animals. In conclusion Initial studies showed 99mTc Alendronate complex has excellent potential as a diagnostic bone scintigraphy agent.