Baxter International on Thursday recalled nearly all of its heparin blood-thinning products six weeks after they were linked to severe allergic reactions in some patients.

The full recall was delayed until Thursday to ensure that another manufacturer would have enough supply to prevent a shortage. Heparin is vital in many medical and surgical procedures.

The company’s heparin products have been associated with as many as four deaths and more than 400 reports of severe allergic reactions, the FDA said in January.

The FDA has acknowledged it didn’t inspect a Chinese plant that supplies the active ingredient for Baxter’s heparin before approving it because the agency mixed up the plant’s name with a different company.

The raw ingredient in heparin is derived from the lining of pigs’ intestines and comes primarily from China.

Baxter recalled its multidose vials of heparin on Jan. 17, but had not recalled its single-dose individual vial products and a device containing heparin called a Hep-Lock, used to flush intravenous lines to ensure that they aren’t blocked by blood clots.

There have been no reports of allergic reactions in patients using Hep-Locks on their IV lines, said Sandra Kweder, deputy director of FDA’s Center for Drug Evaluation and Research. She called Thursday’s recall of Hep-Locks “precautionary.”

Because Baxter supplied half the heparin used in clinical settings in the USA, the FDA agreed that a full recall could be medically dangerous. Since that time, the FDA has worked with the nation’s other main producer of heparin, APP Pharmaceuticals, to ensure that it had the capacity to produce the drug, which is crucial in surgical applications.

“Today, APP is now able to adequately supply the U.S. market,” so Baxter was free to do a full recall, Kweder said.

The only Baxter products remaining on the market that contain heparin are premixed bags of IV solutions, but there have…