In late 2007 and early 2008, a cluster of adverse events in patients receiving Heparin Sodium Injection occurred in the United States and in some countries in Europe. The adverse events were reported as being "allergic type" reactions, chiefly characterized by acute hypotension, nausea, and shortness of breath. The root cause of the cluster of adverse events was determined to be a contamination of the heparin by oversulfated chondroitin sulfate. The isolation and structure determination of this contaminant was accomplished by an FDA-led consortium of academic and government laboratories and independently by Baxter Healthcare, whose vial products were first identified in the USA as being associated with the adverse events. Oversulfated chondroitin sulfate was shown to produce acute hypotension in animal models, demonstrating that it was most likely the causative agent responsible for certain of the reported adverse events in patients receiving the contaminated heparin products.