Evaluation of ^99mTc tetrofosmin formulation change on syringe residual

Objectives In 2012 the commercial formulation was changed. Our primary aim was to compare formulations of ^99mTc-tetrofosmin (A=old and B=new) for residual in disposable plastic syringes. Our secondary aim was to analyze what effect rinsing the syringe had on residual activity for the currently available formulation (B).

Methods Data was collected previously on 41 non-rinsed clinic dosages from formulation A that were assayed before and after administration. 61 non-rinsed clinic dosages from formulation B were assayed before and after administration and percent residual activity was compared with formulation A using an independent t-test. To compare the effect of rinsing, 209 dosages rinsed with normal saline from formulation B were assayed before and after administration and compared to non-rinsed clinic formulation B dosages. In addition, 30 dosages from formulation B were prepared in the nuclear pharmacy according to package insert instructions, assayed before and after emptying, then rinsed and re-assayed.Formulation B rinsed verses not rinsed in both settings was analyzed using a two-way ANOVA model.

Results There was no statistically significant difference between Formula A and B mean syringe residual (t(100)=-0.08, p=0.94). The average syringe residual for formula A and B were 15.5% (95%CI: 13.7%-17.3) and 15.4% (95%CI: 14.2%-16.6) respectively. There was a statistically significant difference between residual pre- and post-rinsing, both in the clinic setting and in the pharmacy setting. Rinsed syringes had a 6.1% (95%CI: 4.9-7.4) lower residual proportion than not rinsed syringes.

Conclusions The newer formulation of ^99mTc tetrofosmin did not show any significant difference in syringe residual when compared to the older formulation. However, rinsing with normal saline significantly affected the administered dose. Residual syringe activity should be investigated as a part of ongoing quality assurance when introducing new syringes, new drugs, or new formulations of current drugs.