Sanofi heparin drug impurity found in 4 countries

A logo of pharmaceutical company Sanofi Aventis is seen in Ambares near Bordeaux, southwestern France, September 20, 2006.

LONDON (Reuters) - Batches of Sanofi-Aventis's blood-thinning heparin injection Lovenox have been found to contain small amounts of impurity in Britain, Sweden, Spain and Australia, officials said on Thursday.

Lovenox is Sanofi's top-selling drug, with sales last year of 2.6 billion euros ($4.1 billion).

Sanofi spokesman Salah Mahyaoui said the problem only involved a small number of batches and there were no reports of patient injuries.

"It affects a very limited number of batches ... and it's very low concentration (of impurity)," he said by telephone from Paris.

The Swedish Medical Products Agency said it was withdrawing a small number of contaminated batches of the drug, which is also known as Clexane or Klexane, as a precaution.

The move follows similar withdrawals by Australian authorities on Wednesday and by Spanish regulators last week, Mahyaoui said.

In Britain, the Medicines and Healthcare products Regulatory Agency stopped short of withdrawing the product. It said doctors could continue to use the drug but should be vigilant to any adverse reactions.

It added there was currently no evidence that the presence of very small amounts of over-sulphated chondroitin sulphate in the medicine was associated with any risk to patients.

The latest discoveries follow a series of recent contamination problems with different heparin products in the United States and Germany, which have led to a number of adverse drug reactions (ADRs) in these countries.

"It is important to note that there is no evidence of any increase in the number of ADRs as has been seen in other countries with other heparin products," the British agency said.

In the United States, tainted heparin from China was used by at least 81 patients who died soon afterwards. They suffered serious allergic reactions, with plummeting blood pressure, swelling of the larynx and other severe symptoms.

Adverse reactions seen in the United States and Germany were from heparin products primarily manufactured by Baxter International Inc and Rotexmedica, respectively.

Sanofi's Mahyaoui said the problems with Lovenox were on a much smaller scale to those seen earlier.

"This impurity was found in a very low concentration, particularly in comparison with what has been observed in some other situations with unfractionated heparins in the United States and Germany," he said.

Shares in Sanofi ended 0.6 percent higher at 49.91 euros. Given the precautionary nature of the action by health authorities and the low level of contamination, analysts said the issue was unlikely to have a significant commercial impact.

Dresdner Kleinwort expects Sanofi to report first-quarter Lovenox sales up 6 percent at 672 million euros when it unveils financial results on April 30.

(Editing by Will Waterman)