MONDAY, Dec. 19, 2005 (HealthDay News) -- Acting at the request of the FDA, the makers of NeutroSpec, an imaging agent approved to diagnose appendicitis, are voluntarily withdrawing the product from the market.
The action came after reports of two deaths and 20 "serious and life-threatening" adverse events linked to use of NeutroSpec, the agency said.
The serious adverse events included cardiopulmonary failure, central nervous system reactions, and infusion reactions. Some of the patients had to be admitted to intensive care, Dr. Sandra Kweder, deputy director of the Office of New Drugs at the FDA's Center for Drug Evaluation and Research, said at a news conference Monday.
In addition, there were 46 other patients who had similar but less severe reactions. Most of the patients ranged in age from 45 to 80 and older, although one was a teenager.
"The company made the decision to suspend marketing based on the events being life-threatening and the availability of other means to diagnose appendicitis that don't carry these risks," Kweder said. "They are urging health-care providers to stop using existing stocks, and to contact the company regarding their return."
The reactions occurred within minutes of the drug's administration by injection.
"Most of the patients, but not all of them, did have some sort of underlying cardiac or lung condition that might somehow have placed them at high risk for an event but they may not have been ill at that time," Kweder said. "We don't know the specific way that NeutroSpec and these adverse events is related, but the consistent characteristics of events in the patients makes it likely they were due to NeutroSpec.
NeutroSpec (Technetium 99m Tc Fanolesomab) is a murine or mouse monoclonal antibody tagged with Technetium, a radioactive molecule that allows it to be seen on an imaging scan. The product is made by Palatin Technologies Inc. and marketed by Mallinckrodt.
"The antibody seeks out and finds white blood cells," said Dr. George Mills, director of the Division of Medical Imaging and Radiopharmaceutical Drug Products at the FDA's Center for Drug Evaluation and Research. "Technetium labels to the monoclonal antibody, which binds to white blood cells producing a hot spot on the imaging so we can identify the site of the infection."
The FDA approved NeutroSpec in July 2004 to help diagnose appendicitis in patients aged 5 years and older who do not have the typical signs of appendicitis.
Approval was based on tests in 523 individuals who experienced a very low rate of shortness of breath or declines in blood pressure. "None of the cases were severe," Kweder said.
Since NeutroSpec's approval, an estimated 11,000 patients have received the product. The company estimated that 60 percent of those cases were to diagnose osteomyelitis, an infection of the bone, and an additional percentage to diagnose off-label infections such as fever without a known source. It's unclear how many of the uses were for the approved indication -- diagnosing appendicitis, Kweder said.
Kweder also said she didn't know what risk, if any, the other infections posed.
"We have no reason to believe that that's related," she said. "We're going to be working closely with the company to understand what is causing these events."
The reactions also don't appear to be classic allergic reactions, she said.
The FDA is urging all health-care providers to stop using NeutroSpec and to contact either the company or their distributor about returning existing stocks.
The FDA plans to take information about NeutroSpec to an advisory committee meeting in 2006.
In the meantime, Kweder said she expects NeutroSpec to be available as an investigational new drug in cases where there are no alternatives.
More information
View the public health advisory at the FDA.
