ga-68-dotatoc - Medication Listings

11.1 Chemical Characteristics Ga 68 DOTATOC Injection is a radioactive diagnostic agent for intravenous administration. It contains 3.6 mcg/mL (DOTA-0-Phe1-Tyr3) octreotide, 18.5 MBq/mL to 148 MBq/mL (0.5 mCi to 4 mCi/mL) of Ga 68 DOTATOC at calibration time, and ethanol (10% v/v) in sodium chloride (9 mg/mL) solution (approximately 14 mL volume). Ga 68 DOTATOC Injection is a sterile, pyrogen free, clear, colorless, buffered solution, with a pH between 4 to 8. Ga 68 DOTATOC, also known as Gallium-68 (DOTA0-Phe1-Tyr3) octreotide, is a cyclic 8 amino acid peptide with a covalently bound chelator (DOTA). The peptide has the amino acid sequence: H-D-Phe-Cys-Tyr-D-Trp-Lys-Thr-Cys-Thr-OH, and contains one disulfide bond. Ga 68 DOTATOC has a molecular weight of 1489.65 g/mol and its chemical structure is shown in Figure 1. Figure 1: Chemical Structure of Ga 68 DOTATOC Gallium-68 labeled 2-[4-[2-[[(2R)-1-[[(4R,7S,10S,13R,16S,19R)-10-(4-aminobutyl)-4-[[(2R,3R)-1,3-dihydroxybutan-2-yl]carbamoyl]-7-[(1R)-1-hydroxyethyl]-16-[(4-hydroxyphenyl)methyl]-13-(1H-indol-3-ylmethyl)-6,9,12,15,18-pentaoxo-1,2-dithia-5,8,11,14,17-pentazacycloicos-19-yl]amino]-1-oxo-3-phenylpropan-2-yl]amino]-2-oxoethyl]-7,10-bis(carboxymethyl)-1,4,7,10-tetrazacyclododec-1-yl]acetic acid. Figure 1 11.2 Physical Characteristics Table 3 and Table 4 display the principal radiation emission data and physical decay of Ga 68. Gallium-68 (Ga 68) decays with a half-life of 68 minutes to stable Zn 68: 89% through positron emission with a mean energy of 836 keV followed by emission of two 511 keV annihilation photons (178%), 10% through orbital electron capture (with associated X-ray or Auger emissions), and 3% through 13 gamma transitions from 5 excited levels of the daughter Zn 68 nucleus. The most probable prompt gamma emission is a 1088 keV gamma with a 3.2% per decay probability. Table 3: Principal Radiation Emission Data (>1%) Radiation/Emission % Disintegration Mean Energy (MeV) beta+ 88% 0.8360 beta+ 1.1% 0.3526 gamma 178% 0.5110 gamma 3% 1.0770 X-ray 2.8% 0.0086 X-ray 1.4% 0.0086 Table 4: Physical Decay Chart for Gallium Ga-68 Minutes Fraction Remaining 0 1.000 15 0.858 30 0.736 60 0.541 90 0.398 120 0.293 180 0.158 360 0.025 11.3 External Radiation Gamma constant: 1.8 × 10 -4 mSv/hr per MBq at 1 meter [0.67 mrem/hr per mCi at 1 meter] Table 5 displays the radiation attenuation by lead shielding of Ga 68. Table 5: Radiation Attenuation of 511 keV Photons by Lead (Pb) Shielding Shield Thickness (Pb) mm Coefficient of Attenuation 6 0.5 12 0.25 17 0.1 34 0.01 51 0.001