CARDIOGEN-82 Solution for injection Ref.[10196] Active ingredients: Rubidium ⁸²Rb chloride

11.1 Chemical Characteristics

CardioGen-82 contains accelerator-produced Sr 82 adsorbed on stannic oxide in a lead-shielded column and provides a means for obtaining sterile nonpyrogenic solutions of rubidium Rb 82 chloride injection. The chemical form of Rb 82 is ⁸²RbCl.

The amount (millicuries) of Rb 82 obtained in each elution will depend on the potency of the generator. When eluted at a rate of 50 mL/minute, each generator eluate at the end of elution should not contain more than 0.02 microcurie of Sr 82 and not more than 0.2 microcurie of Sr 85 per millicurie of rubidium Rb 82 chloride injection, and not more than 1 microgram of tin per mL of eluate.

11.2 Physical Characteristics

Rb 82 decays by positron emission and associated gamma emission with a physical half-life of 75 seconds. ⁴ Table 5 shows the annihilation photons released following positron emission which are useful for detection and imaging studies.

The decay modes of Rb 82 are: 95.5% by positron emission, resulting in the production of annihilation radiation, i.e., two 511 keV gamma rays; and 4.5% by electron capture, resulting in the emission of "prompt" gamma rays of predominantly 776.5 keV. Both decay modes lead directly to the formation of stable Kr-82.⁴

TABLE 5. Principal Radiation Emission Data:

The specific gamma ray constant for Rb 82 is 6.1 R/hour-millicurie at 1 centimeter. The first half-value layer is 0.7 centimeter of lead (Pb). Table 6 shows a range of values for the relative attenuation of the radiation emitted by this radionuclide that results from interposition of various thicknesses of lead. ⁵ For example, the use of a 7.0 centimeter thickness of Pb will attenuate the radiation emitted by a factor of about 1,000.

TABLE 6. Radiation Attenuation by Lead Shielding:

Sr 82 (half-life of 25 days (600 hrs.)) decays to Rb 82. To correct for physical decay of Sr 82, Table 7 shows the fractions that remain at selected intervals after the time of calibration.

TABLE 7. Physical Decay Chart: Sr 82 half-life 25 days:

* Calibration time

To correct for physical decay of Rb 82, Table 1 shows the fraction of Rb 82 remaining in all 15 second intervals up to 300 seconds after time of calibration [see Dosage and Administration (2.6, 2.7)].