The cardiac nuclear stress test drugs regadenoson and adenosine may hold a greater MI and mortality risk in patients with signs and symptoms of unstable angina than had previously been reported, the FDA cautioned in a warning.

Regadenoson (Lexiscan) and adenosine (Adenoscan) have been approved by the FDA for use during cardiac nuclear stress tests in patients who cannot undergo an exercise stress test to identify coronary artery disease. In a drug safety communication, the FDA alerted physicians that MI and death have occurred in patients who received infusions of one or the other drug.

“Both drugs present a risk to patients, especially to those with ongoing cardiac ischemia,” the FDA wrote.  “Some cases of myocardial infarction and death have occurred in patients with pre-existing unstable angina or cardiovascular instability.”

The warnings and precautions section of the two drugs’ labels already informed physicians of possible MI and mortality risks. Due to recent reports in the FDA’s Adverse Event Reporting System (FAERS) database and in the medical literature, the agency updated its recommendations and approved changes to the drug labels.  

The FDA’s review of FAERS data found 26 cases of MI and 29 cases of death that occurred during administration of regadenoson and six cases of MI and 27 cases of death after administration of adenosine. The adverse events tended to occur within six hours of administration.

In addition, the FDA identified deaths that occurred after administration of one or the other drug with exercise stress testing; that use is not approved by the FDA. The FDA looked at cases starting from the date of approval for each drug.

The agency advised physicians to screen patients prior to a stress test to evaluate their eligibility and to avoid using the drugs in patients with symptoms or signs of acute MI. It recommended that cardiac resuscitation equipment and trained staff should be on hand before administering regadenoson and adenosine.

The FDA said the risk is rare but serious, and that limitations in the currently available data made it difficult to identify risk differences between the two drugs. Physicians should report any adverse events involving regadenoson and adenosine to FDA MedWatch.