US experts have identified the substance which contaminated made-in-China heparin blood thinner and possibly caused the deaths of 19 patients and severe allergic reactions in hundreds of others.
The US Food and Drug Administration said Wednesday that the anticoagulant drug, commonly used to treat victims of heart attacks, was tainted with oversulfated condroitin sulfate (OCS), a man-made chemical.
The chemical was detected after the FDA linked heparin injections made in China and sold by Baxter International pharmaceuticals to severe allergic reactions and possibly to the deaths.
Most of the active ingredients in the drug came from a plant in Changzhou, China working with Wisconsin-based Scientific Protein Laboratories, which supplies Baxter.
On February 28 Baxter recalled all its heparin from the US market, and last week US health authorities ordered a halt to all imports of heparin blood-thinners to test them for contaminants.
Janet Woodcock, the director of the FDA's Center for Drug Evaluation and Research, said the OCS is not ordinarily found in nature and had to be chemically modified by humans.
"We are investigating how it got in" to the heparin, she said, noting that it also chemically resembles heparin, making it harder to detect.
"We cannot rule in or out whether this was accidentally or deliberately introduced into the product," she said.
"We don't have any evidence if it was intentionally introduced" to the Baxter heparin.
Last week Woodcock said the FDA was working with health authorities in Germany and Japan, where pharmaceuticals have recalled apparently contaminated heparin products linked to allergic reactions.