Endo Health Solutions’ (ENDP) popular pain-killer drug opana may cause a “serious blood disorder” if misused, the U.S. Food and Drug Administration warned on Thursday.

The disorder, called thrombotic thrombocytopenic purpura (TTP), has resulted in kidney failure in some cases and at least one death.

The FDA observed the negative reaction to the drug when people abused the extended-release tablet by injecting opana into their bloodstream.

TTP causes blood to clot in small blood vessel throughout the body, which can limit or block food flow to the body’s organs, including the kidneys, brain and heart. The FDA warned that TTP can cause death or lead to other complications with permanent damage such as brain damage or a stroke.

The FDA said the disease appears to only occur when the drug is abused and injected.

Shares of Endo Health are trading slightly higher Thursday afternoon to $30.71.

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