Stability Of Stabilized Tc-99m-D,L-Hmpao Stored In Vials And Syringes

Our objective was to determine the stability of stabilized Tc-99m-hexamethylpropylene amine oxime (Tc-99m-D,L-HMPAO) dispensed by vial and syringe, with the storage time and labeling activity varied. Methods: Tc-99m-D,L-HMPAO was labeled according to the manufacturer's instructions, but with modification of the (TcO4Na)-Tc-99m activity. Two groups were prepared: 1,110 MBq (30 mCi) and 2,600-3,700 MBq (70.3-100 mCi). Five minutes after labeling, the radiochemical purity (RCP) of the vial content was determined. Afterward, the same activity was distributed into two 2-mL syringes and into the manufacturer's vial. In one of the syringes, the radiopharmaceutical stayed in contact with the needle for 4 h. At 2 and 4 h after labeling, the RCP of the vial and syringe content was checked and compared. Results: The mean RCP of stabilized Tc-99m-D,L-HMPAO labeled with 1,110 MBq (30 mCi) and stored in a vial decreased from 93.1% at 5 min to 92.1% at 2 h and to 91.1% at 4 h. With storage in a syringe, the RCP decreased from 89.8% at 2 h to 88.7% at 4 h. This diminution increased for labeling with higher activities (2,600-3,700 MBq [70.3-100 mCi]), ranging from 91.4% at 5 min, 89.0% at 2 h, and 85.3% at 4 h in a vial and from 85.9% at 2 h to 80.2% in a syringe. (TcO2)-Tc-99m and secondary Tc-99m-HMPAO were themain impurities at t = 0. (TcO4-)-Tc-99m was an impurity that increased with time in both vials and syringes but significantly so in syringes. All these impurities were higher with labeling activities in the range of 2,600-3,700 MBq (70.3-100 mCi). Contact of the needle with Tc-99m-D,L-HMPAO sharply decreased the RCP to 57.1% at 4 h. Conclusion: The RCP of stabilized Tc-99m-D,L-HMPAO decreases significantly in both vials and syringes with high labeling activities. The product is less stable when stored in a syringe than in a vial. The fraction of dose in contact with the needle affects the RCP results.