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The FDA said the action came after reports of serious allergic reactions and hypotension in patients who received high "bolus" doses of the blood-thinning drug. The serious reactions included difficulty breathing, nausea, vomiting, excessive sweating, and rapidly falling blood pressure that can lead to life-threatening shock. Four people have died after receiving heparin, although the relationship to the drug is unclear.

"FDA concurs with Baxter's decision to halt manufacture of heparin sodium in multiple-dose vials," said Dr. Janet Woodcock, the FDA's deputy commissioner for scientific and medical programs. "FDA is vigorously investigating to determine the root cause of these serious reactions … in the meantime, patients and health care professionals who cannot obtain alternative sources of heparin should use caution in administering any Baxter multiple-dose vials that remain."

Heparin is commonly used before certain types of surgery, including coronary artery bypass graft surgery, and in kidney patients before they undergo dialysis.

Over one million multiple-dose vials of heparin are sold monthly in the United States, with half of the vials manufactured by Baxter