Heparin is a medication commonly used to prevent blood clots during a heart a attack. Much of the Heparin used in the United States is made by Baxter International, which, in turn, buys its supplies from a Chinese manufacturer. The Food and Drug Administration reported last week that 21 deaths resulted from the use of heparin from Baxter. It’s unclear how exactly the medication contributed to the deaths; an allergic reaction is suspected. It is also possible that those who died were already seriously ill and would have died whether or not heparin was used.

Heparin and enoxaparin (Lovenox) are blood thinners critical in the treatment of heart attacks and during balloon and stent procedures. They prevent blood clots from forming inside a coronary artery.

Baxter International responded to the reported deaths by recalling nearly all of its heparin products. Another supplier, APP Pharmaceuticals, should be able to meet the demand for this life-saving drug.

Read more about drugs used in treating a heart attack.