Gadobutrol, a gadolinium-based contrast agent approved by the FDA in 2011, has a low allergic-like reaction rate similar to other gadolinium-based agents, according to a recent study published by Radiology.

Daniel M. Mandell, MD, PhD, of Toronto Western Hospital, and colleagues studied data from more than 30,000 gadolinium-enhanced MR imaging examinations that used gadobutrol, noting each time it was reported the patient had allergic-like reaction.

Mandell and colleagues explained that allergic-like reactions were the focus of their study, not physiologic reactions.

“We determined the frequency of allergic-like reactions as differentiated from physiologic reactions,” the authors wrote. “As is emphasized in the current American College of Radiology manual on contrast media (version 9), this distinction between allergic-like and physiologic reactions is important because an allergic-like reaction is a reason to administer premedication for subsequent gadolinium contrast material, whereas a physiologic reaction is not.”

Overall, there were a total of 96 allergic-like reactions to gadobutrol, giving the agent a reaction rate of 0.32 percent. That number is higher than the 0.02 percent rate derived from post-market surveillance, but Mandel et al. said that was expected; surveillance data is higher by nature due to physician self-reporting.

The 96 allergic-like reactions were recorded in 82 patients. Eight patients went through two reactions, and one patient experienced seven.

Seventy-eight of the 82 patients had mild reactions to gadobutrol, three patients had moderate reactions, and one patient had a severe reaction.

“The one severe reaction occurred in a 50-year-old woman who underwent outpatient contrast-enhanced breast MR imaging and who previously received intravenous gadolinium contrast material with no reaction,” the authors wrote. “However, she had a considerable history of other allergic-like reactions, including a severe allergic-like reaction to iodinated contrast material and reactions to several medications. Difficulty with breathing and swallowing developed within 8 minutes of the injection, the code team was called, and a 50-minute resuscitation effort in the imaging department was required to stabilize the patient. She was then transferred to the intensive care unit.”

More than 15 percent of the reactions were delayed, but they still occurred on the same day or the following day. Urticaria (hives) was the most common symptom of a delayed reaction.

The authors noted that their findings were significantly lower than a meta-analysis of clinical trial data, which reported a 4 percent reaction rate for gadobutrol in 2011.

“The meta-analysis did not discriminate among physiologic responses and allergic-like reactions to gadobutrol, potentially accounting for the higher rate,” the authors wrote. “Also, the meta-analysis included data from fewer than 5000 patients that were retrospectively gathered from 34 different trials; thus, there may have been heterogeneity in the diagnosis of adverse reactions.”

Mandel and colleagues then compared their findings to similar studies of other contrast agents.

“Our allergic-like reaction rate of 0.32 percent to gadobutrol favorably compares with a rate of 0.67 percent  that was reported in a prospective study of gadoteridol, another macrocyclic nonionic agent, and a rate of 0.76 percent that was reported in a prospective study of gadobenate dimeglumine, a linear nonionic agent,” the authors wrote. “Neither of these studies differentiated between allergic-like and physiologic reactions, potentially explaining their higher reaction rates.”