PET Scan Drug Side Effects Being Investigated

The U.S. Food and Drug Administration (FDA) just issued a notification to the medical imaging community and the public concerning the potential for inadvertent, increased radiation exposure in patients who underwent or will undergo cardiac positron emission tomography (PET) scans with rubidium (Rb)-82 chloride injection from CardioGen-82, a device manufactured by Bracco Diagnostics, Inc.

The CardioGen-82 is one of a variety of nuclear medicine scans and is a radionuclide generator that produces the radioactive drug Rb-82 chloride injection, which evaluates the heart. The Rb-82 emits the radiation detected in a PET scan and is a medical isotope with a short half-life (75 seconds), and is derived from strontium-82 (Sr-82), which has a half-life of 25 days. Rb-82 is collected from the generator column by injecting a solution of normal saline through the column. Normally, only the Rb-82 is released into the solution, while the strontium remains attached to the column.

The FDA has received reports of two patients who received more radiation than expected from CardioGen-82. The excess radiation was due to strontium isotopes which may have been inadvertently injected into the patients due to a “strontium breakthrough” problem with CardioGen-82.

FDA is actively investigating the root cause of the CardioGen-82 failure and will promptly notify the public with updates. Also, efforts include discussions with the Nuclear Regulatory Commission.

Although the FDA believes the risk of harm from this exposure is minimal, any unnecessary exposure to radiation is undesirable. The agency said the estimated amount of excess radiation involved in these two patients is similar to what a patient may expect to receive with cumulative exposure to other types of heart scans.

The FDA also advises healthcare professionals to closely follow the required testing and quality control procedures essential to help detect strontium breakthrough from CardioGen-82. Other heart scans provide information very similar to CardioGen-82 and professionals are encouraged to consider these alternatives while FDA completes its investigation of the reported cases of excess radiation exposure. If CardioGen-82 is used, apply special attention to the steps to minimize strontium breakthrough risks indicated in the prescribing information and detailed by the FDA on its website at: http://www.fda.gov/Drugs/DrugSafety/ucm263112.htm.

Patients planning to undergo a heart scan should talk to their healthcare professional if they are unsure of the type of planned heart scan and the radiation risks with that scan. Also, said the FDA, patients planning to undergo a CardioGen-82 scan may wish to delay their procedure until the radiation issue is resolved.

At this time, it is unknown whether this safety issue is due to a product problem involving generator failure or due to user error, or a combination of both.

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