succimer - Generic Medications

CHEMET (succimer) is an orally active, lead chelating agent. The chemical name for succimer is meso 2, 3-dimercaptosuccinic acid (DMSA). Its empirical formula is C 4 H 6 O 4 S 2 and molecular weight is 182.2. The meso -structural formula is: Succimer is a white crystalline powder with an unpleasant, characteristic mercaptan odor and taste. Each CHEMET opaque white capsule for oral administration contains medicated beads with 100 mg of succimer and the following inactive ingredients: povidone, sodium starch glycolate, and sugar spheres. The capsule shell contains benzyl alcohol, butylparaben, edetate calcium disodium, gelatin, methylparaben, propylparaben, sodium lauryl sulfate, sodium propionate, titanium dioxide, and is imprinted with edible black ink. Chemical Structure

11.1 Chemical Characteristics NEPHROSCAN is a sterile, single-dose kit for the preparation of Technetium Tc 99m Succimer Injection a radioactive diagnostic agent, for intravenous use. The active ingredient, succimer is meso-2,3-dimercaptosuccinic acid with a molecular weight of 182.22 g/mol. The chemical structure of succimer is shown below. Subsequent to radiolabeling with sodium pertechnetate Tc 99m, the active moiety technetium Tc 99m succimer is obtained in situ. Each vial contains 1 mg succimer, 0.1 mg ascorbic acid, 0.42 mg stannous (tin) chloride dihydrate, 0.02 mg hydrochloric acid and 0.2 mg sodium hydroxide as a white-yellowish to off-white lyophilized powder. In addition, after radiolabeling with sodium pertechnetate Tc 99m injection, each vial contains up to 1,480 MBq (40 mCi) of technetium Tc 99m succimer in 0.9% sodium chloride injection as a sterile, clear, and colorless solution. pH of the final solution is between 3 and 3.5. FDA approved pH specifications differ from USP. Chemical Structure 11.2 Physical Characteristics Technetium Tc 99m decays by isomeric transition with a physical half-life of 6.02 hours. The principal photon that is useful for detection and imaging studies is listed in Table 3. Table 3 Principal Radiation Emission Data for Technetium Tc 99m Radiation/ Emission Mean % / Disintegration Mean Energy (keV) Gamma 2 89.07 140.5 To correct for physical decay of this radionuclide, the fractions that remain at selected intervals after the time of calibration are shown in Table 4. Table 4 Physical Decay Chart for Tc 99m, half-life 6.02 hours Hours Fraction Remaining Hours Fraction Remaining 0 Calibration time 1.000 7 0.447 1 0.891 8 0.398 2 0.794 9 0.355 3 0.708 10 0.316 4 0.631 11 0.282 5 0.562 12 0.251 6 0.501 11.3 External Radiation The specific gamma ray constant for technetium Tc 99m is 0.78 R/hr-mCi at 1 cm. The first half value layer is 0.017 cm of Pb. To facilitate control of the radiation exposure from millicurie amounts of this radionuclide, the use of a 0.25 cm thickness of Pb will attenuate the radiation emitted by a factor of about 1,000. Table 5 displays the radiation attenuation by lead shielding. Table 5 Radiation Attenuation by Lead (Pb) Shielding Shield Thickness (Pb) mm Coefficient of Attenuation 0.02 0.5 0.08 0.1 0.16 0.01 0.25 0.001 0.33 0.0001