Radiochemical purity and stability of generic Tc-99m Exametazime compared to Tc-99m Ceretec

Objectives Tc-99m Ceretec (GE Healthcare) is used to evaluate cerebral blood flow. Recently a generic version of Tc-99m exametazime has been introduced. The objective of this study was to evaluate the radiochemical purity and stability of generic Tc-99m exametazime (AnazaoHealth) and compare the results to Tc-99m Ceretec.

Methods Both radiopharmaceutical kits were evaluated at low (50 mCi) and high activity (80 mCi). Kits were formulated according to manufacturers instructions. For each specific preparation, the radiochemical purity and stability was evaluated up to 7 or 8 hours after formulation using miniaturized chromatography consisting of Whatman 17 with ethyl acetate. For each specific chromatographic evaluation, three replicate samples were analyzed. Data was summarized by calculating mean percent radiochemical purity.

Results At low activity, the initial radiochemical purity of generic Tc-99m exametazime and Tc-99m Ceretec was 87% and 95%, respectively. The radiochemical purity of generic Tc-99m exametazime remained greater than 80% up to 6 hours after formulation. At 7 hours after formulation the radiochemical purity of generic Tc-99m exametazime was 78%, indicating preparation failure. The radiochemical purity of Tc-99m Ceretec remained greater than 80% up to 7 hours after formulation. At high activity, the initial radiochemical purity of generic Tc-99m exametazime and Tc-99m Ceretec was 85% and 95%, respectively. For both formulations the radiochemical purity remained greater than 80% up to 6 hours. At 7 hours post formulation, the radiochemical purity of generic Tc-99m exametazime and Tc-99m Ceretec were 78% and 79%, respectively, indicating preparation failure.

Conclusions The radiochemical purity and stability of generic Tc-99m exametazime and Tc-99m Ceretec was greater than 80% up to 6 hours post formulation at both low and high activity. At 7 hours post formulation, only the low activity Tc-99m Ceretec preparation maintained a labeling efficiency greater than 80%