The U.S. Food and Drug Administration, for the first time, has conclusively linked deaths of patients infused with the blood thinner heparin to a foreign substance found in specific lots of the drug made by Deerfield-based Baxter International Inc. In an interview Tuesday with the Tribune, the FDA said it completed its review of 93 death reports related to heparin that the agency received from Jan. 1 to March 31, a period when there was a dramatic spike in potentially deadly allergic reactions from patients who had been injected with heparin. The popular blood thinner is used widely in large dosages, often before patients have dialysis or heart surgery.

Of 10 reports of death from severe shock known as anaphylaxis or hypotension, three of those could be traced to lot numbers of Baxter products that tested positive for an animallike substance known as oversulfated chondroitin sulfate. Heparin lot numbers were not known for the other seven deaths from anaphylaxis or hypotension, so the FDA could not determine whether those 7 patients received heparin contaminated with the substance.

"We have what looks like a cause and effect in some patients," Dr. Janet Woodcock, director of the FDA's Center for Drug Evaluation and Research, said in an interview, referring to the three deaths linked to contaminated heparin. "We know that they got contaminated heparin, and they died subsequently. This is one of the final links in the chain." Baxter recalled its heparin products in February in the wake of the spike in the number of the allergic reactions. In recent months, federal health officials and Baxter believe the oversulfated chondroitin sulfate was intentionally put into the product from suppliers in China.

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