Stability of stabilized 99mTc-D,L-HMPAO stored in vials and syringes.

Our objective was to determine the stability of stabilized 99m Tc-hexamethylpropylene amine oxime ( 99m TC-D,L-HMPAO) dispensed by vial and syringe, with the storage time and labeling activity varied. Methods: 99m Tc-D,L-HMPAO was labeled according to the manufacturer's instructions, but with modification of the 99m TcO 4 Na 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 99m Tc-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 2h and to 91.1 % at 4h.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. 99m TcO 2 and secondary 99m Tc-HMPAO were the main impurities at t = O. 99m TcO 4 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 99m Tc-D,L-HMPAO sharply decreased the RCP to 57.1% at 4 h. Conclusion: The RCP of stabilized 99 mTc-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.