Evaluation of compatibility and stability of filtered 99mTc-sulfur colloid when combined with indocyanine green dye

2414 Objectives It is a common practice to administer dyes and radiopharmaceuticals separately for the localization of sentinel nodes in patients with biliary tract malignancies. The objective of the study is to evaluate the chemical properties and particle size of filtered 99mTc-sulfur colloid (FSC) before and after it is combined with indocyanine green for injection, USP (IG). This study also evaluates the compatibility and stability when combining the two for the possibility of a single injection. Methods 99mTc-SC (Pharmalucence, Bedford, MA) was prepared according to the package insert and the final preparation was filtered through a sterile 0.2-µm filter. IG dye (Akorn, Incorporated, Lake Forest, IL) was also prepared as per package insert. In a sterile syringe, 0.25 mL of 14.8 MBq (400 μCi) FSC was mixed with 0.25 mL of 1.25 mg IG dye in a 1:1 for a total solution volume of 0.50 mL. The radiochemical purity (RCP) and pH values of FSC were obtained immediately, and at 1 and 2 hours post-preparation. Particle size was analyzed using an electron microscope (FEI Tecnai 12 TEM, FEI Company, Hillsboro, OR) immediately and at 2 hours. In addition, bacterial endotoxins and sterility were tested at two hours post-preparation with the Endosafe PTS 100 (Charles River Laboratories, Charleston, SC). Results The average RCP value was 97.6 ± 2.2% (n = 24). The average pH value was 5.47 ± 0.29 (n = 24). Evaluation of the particle size of FSC with the IG dye was determined by electron microscopy to be an average of 62 ± 30nm (n = 271) at zero hour and 71 ± 34nm (n = 215) at two hours. This was compared to the filtered 99mTc-SC without the IG dye to be an average of 71 ± 41nm (n = 41). Measurements of unfiltered 99mTc-SC were recorded at 253 ± 192nm (n = 21) for additional comparisons. All two hour samples passed bacterial endotoxins and sterility tests. Conclusions The chemical properties and particle size of FSC were not impacted by the addition of IG, and thus it is suitable to combine FSC and IG in the same syringe for administration