Baxter International has temporarily suspended production of certain doses of its blood-thinning agent heparin after reports of severe allergic reactions and US regulators are advising doctors to switch suppliers.

The company has stopped manufacturing multiple-dose vials of heparin due to reports of an increase in serious allergic reactions and low blood pressure in patients who receive high ‘bolus’ doses of the drug. These reactions have included difficulty in breathing, nausea, vomiting, excessive sweating, and rapidly falling blood pressure that can lead to life-threatening shock.

The US Food and Drug Administration says that about 350 adverse events associated with Baxter’s product have been reported since the end of last year compared to less than 100 cases in 2007. Four patients died, “although the relationship to the drug is unclear”, the agency stated.

Heparin is derived from pig intestines and has been marketed in the USA since the 1930s. “Millions of patients benefit from the intravenous administration of this drug every year to avoid potentially life-threatening blood clots in the veins, arteries and lungs,” the FDA stated.

Janet Woodcock, the acting director of the FDA's Center for Drug Evaluation and Research, said the agency concurs with Baxter's decision to halt manufacture of heparin in multiple-dose vials, saying it is "vigorously investigating to determine the root cause of these serious reactions”. She added that 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”.

Over one million multiple-dose vials of heparin are sold per month in the USA and half of those are manufactured by Baxter, though it is no longer a big earner for the firm. The FDA added that it is currently investigating whether similar events have been seen with other heparin manufacturers.

The news comes just a month after Baxter voluntarily recalled nine lots of its injectable heparin injection in 1,000-unit vials, citing an increase in adverse patient reactions. Since then, it has received reports of adverse reactions in additional lots of multi-dose vials of 1,000, 5,000 and 10,000 units, and in single-dose vials of 5,000 units when single doses were combined to create a larger bolus dose.

In agreement with the FDA, Baxter is continuing to distribute these products, saying that their removal from the market “would create more risk to the population of patients requiring heparin therapy than the increased potential for experiencing an adverse reaction”.