FDA blames CardioGen overexposure problems on improper usage
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This increased radiation exposure was due to the administration of CardioGen-82 generator eluates that contained excessive concentrations of strontium-82 (Sr-82) and strontium-85 (Sr-85). This excessive release of Sr-82 and Sr-85 in generator eluates is known as "strontium breakthrough," wrote the FDA in its Jan. 12 update. “The FDA believes it is unlikely that this excessive exposure posed significant risks to patients, though exposure to any excessive radiation is undesirable,” the agency said.
CardioGen-82 consists of a generator that is used at clinical sites to produce rubidium (Rb)-82 chloride injection. A CardioGen-82 PET scan is one of a variety of nuclear medicine scans that use radioactive drugs to evaluate the heart.
In its July 26, 2011, Drug Safety Communication, the FDA stated that it had identified deficiencies with the manufacturing procedures for CardioGen-82. “To date, these deficiencies do not appear to have been related to the excessive radiation exposure detected in some patients,” wrote the agency. “The recalled CardioGen-82 generators that were functional following shipping were tested by the manufacturer to identify potential structural or functional causes of strontium breakthrough. None of the tested generators showed signs of breakthrough. FDA continues to work with the manufacturer to resolve their manufacturing deficiencies.”
Bracco had announced in October 2011 that it expected Cardio-Gen to return to the U.S. market early this year. In compliance with FDA requests, the company is currently conducting studies of clinical sites across the U.S. to help assess the extent to which patients may have been exposed to excessive radiation. Participation in this study is voluntary and the preliminary data show that, of 375 patients who were surveyed at 43 clinical sites, 54 patients were planned for further radiation testing because of abnormal screening test results. All 54 patients are from two clinical sites. Both sites appear to have insufficient documentation of compliance with the CardioGen-82 labeling recommendations for strontium breakthrough testing.
The FDA said it will continue to work with Bracco and other federal agencies to better characterize the problems that led to excessive radiation exposure to patients at certain clinical sites. The agency also is working with Bracco to revise the CardioGen-82 labeling to better describe how to use the generator and to implement a plan for the return of CardioGen-82 to the market.