Baxter International was forced to issue a recall of the blood thinning drug heparin after hundreds of cases of serious allergic reactions were reported among patients who were given the drug.

In January 2008, the Centers for Disease Control and Prevention learned of several cases of severe allergic reactions out of Missouri among patients who were treated with heparin during dialysis. After being alerted of these cases, Baxter issued a heparin recall for nine lots of the drug that were linked to the allergy cases.

The Food and Drug Administration subsequently learned that cases of heparin allergic reactions were occurring beyond the nine lots that were initially recalled. As a result, Baxter suspended manufacturing of the drug and issued a complete heparin recall.

Over the beginning of 2008, reports of heparin side effects rose by almost 30 times the number reported during the previous year. Patients have experienced severe allergic reactions that can include breathing problems, increased heart rate and a severe drop in blood pressure that can lead to fatal shock.

Subsequent research by the FDA found that as much as 20% of the heparin in the recalled vials was actually a contaminant which was so similar to heparin that normal tests were unable to detect it. The agency is currently investigating the Chinese plant where Baxter’s heparin was manufactured to determine whether deliberate contamination could have been the cause of the heparin side effects outbreak.