SPL Set ID: d9c291e0-cd0d-43d2-87b4-defefd531942

11.1 Chemical Characteristics Ceretec (kit for the preparation of technetium Tc 99m exametazime injection) prepares a radioactive diagnostic agent for intravenous use. Each unit consists of the following: One 10 mL vial of exametazime containing a sterile, non-pyrogenic, lyophilized mixture of 0.5 mg exametazime, 7.6 mcg stannous chloride dihydrate (minimum stannous tin 0.6 mcg; maximum total stannous and stannic tin 4 mcg per vial) and 4.5 mg sodium chloride, sealed under nitrogen atmosphere with a rubber closure. The product contains no antimicrobial preservative. One vial of cobalt stabilizer containing a sterile, non-pyrogenic solution of 200 mcg cobaltous chloride 6-hydrate in 2 mL of Water for Injection. The chemical name for Exametazime is [(RR,SS)-4.8-diaza-3,6,6,9-tetramethylundecane-2, 10-dione bisoxime]. The molecular formula of exametazime is C 13 H 28 N 4 O 2 , with the following structural formula: Prior to publication of the USAN, exametazime was known as hexamethylpropylene amine oxime (HM-PAO). The name HM-PAO appears in many publications. When sterile pyrogen-free sodium pertechnetate Tc 99m in isotonic saline is added to the vial of exametazime, a Tc 99m complex of exametazime is formed. Chemical Structure 11.2 Physical Characteristics Technetium Tc 99m decays by isomeric transition with a physical half-life of 6 hours. Photons that are useful for imaging studies are listed in Table 3. Table 3: Principal Radiation Emission Data-technetium Tc 99m Radiation Mean % Disintegration Mean Energy (keV) Gamma 2 88.5 140.5 11.3 External Radiation The air-kerma-rate (exposure-rate) constant for technetium Tc 99m is 5.23 m 2 ∙pGy∙(MBq) –1 ∙s –1 [0.795 cm 2 ∙R∙(mCi) –1 ∙h –1 ]. The first half-value thickness of lead (Pb) for technetium Tc 99m is 0.25 mm. A range of values for the relative attenuation of the radiation emitted by this radionuclide that results from interposition of various thicknesses of Pb is shown in Table 4. For example, the use of a 3 mm thickness of Pb will decrease the external radiation exposure by a factor of approximately 1,000. Table 4: Radiation Attenuation by Lead Shielding Shield Thickness (Pb) mm Coefficient of Attenuation 0 . 25 0.5 1 10 –1 2 10 –2 3 10 –3 4 10 –4 5 10 –5 To correct for physical decay of this radionuclide, the fractions that remain at selected intervals relative to the time of calibration are shown in Table 5. Table 5: Physical Decay Chart – Tc 99m half-life 6.03 hours Hours Fraction Remaining Hours Fraction Remaining 0 Calibration time (time of preparation) 1 7 0.447 1 0.891 8 0.399 2 0.795 9 0.355 3 0.708 10 0.317 4 0.631 11 0.282 5 0.563 12 0.252 6 0.502 24 0.063