Abstract
It has been widely reported that technetium-99m (99mTc) succimer adsorbs to traditional plastic syringes significantly (up to 50%), often resulting in lower administered dosages than intended and inaccurate dosing. This is especially problematic in the pediatric population. To improve 99mTc succimer dosing, the authors compared the adsorption of 99mTc succimer in two types of syringes: traditional silicone-coated syringes with non-latex rubber on the plunger (Type A), and inert non-reactive syringes with no silicone coating and no rubber on the plunger (Type B). The residual activity comparisons for the two type of syringes was investigated in a controlled laboratory environment and in a clinical department environment. Methods: 99mTc succimer kits were compounded according to the manufacturer's instructions. For the controlled laboratory aspect of the investigation, a series of 99mTc succimer dosages (0.03 - 0.14 MBq) were drawn into 3-mL Type A silicone-coated or Type B inert non-reactive syringes in 1 mL volume. Thirty min, 1hr, 2hr, and 4 hr later, the syringes were assayed in a dose calibrator, and assayed again after being emptied and rinsed with saline. For the clinical department investigation, the authors examined the radiopharmaceutical documentation and data from 129 99mTc succimer dosages administered in a pediatric department, in which 52 were dispensed in the traditional Type A silicone-coated syringes and 77 were dispensed in Type B inert non-reactive syringes. The dosages were assayed immediately before and after injection. Each injection was followed by flushing with saline. Results: The labeling efficiency of the 99mTc succimer kits was more than 95%. In the laboratory setting, residual activity left in the Type B inert non-reactive syringes was 0.73% (SD ± 0.18%), which was significantly lower than the activity left in the traditional Type A silicone-coated syringes (P<0.0001), which was 20.9% (SD ± 5.6%). The extent of adsorption did not change significantly between 30 min and 4 hours of incubation. The clinical data showed that the residual activity was 6.38 % (SD±2.95%) from dosages dispensed in Type B inert non-reactive syringes and 30.6% (SD±12.5%) from dosages dispensed in the traditional Type A silicone-coated syringes (P<0.001). Conclusion: The inert non-reactive syringes have significantly less residual of 99mTc succimer than silicone based syringes, making it possible to accurately administer calculated doses of 99mTc succimer to pediatric patients.
