(Adds company comments, byline, updates shares) By Susan Heavey WASHINGTON, April 9 (Reuters) - Cubist Pharmaceuticals Inc <CBST.O> is warning doctors that a chemical used in manufacturing rubber has been found in some of its Cubicin injectable antibiotic stored in pumps made by Cardinal Health Inc <CAH.N>, U.S. health regulators said on Wednesday. The chemical, called mercaptobenzothiazole or MBT, is a "potentially significant impurity" that can irritate the skin, Cubist officials wrote in an April 4 letter to health care providers. Laboratory tests have also linked it to an increased risk of tumors in rodents. MBT is an additive used in a variety of rubber products and has been known to seep from medical devices, according to the U.S. Food and Drug Administration, which posted the Cubist letter on its Web site on Wednesday. "The clinical significance of this finding is unknown," Cubist wrote. Both Cubist and the FDA are urging doctors to discontinue use of the ReadyMed pumps, smaller-sized devices that can be used by patients at home. It was also not immediately clear what caused the problem. Cubist spokeswoman Eileen McIntyre said the impurity was found during routine testing but that the contamination was "definitely" linked to Cardinal's pump, not Cubicin. She added it was unclear when the issue would be resolved. "We don't know because Cardinal has to investigate this," she said. Cardinal spokesman Troy Kirkpatrick said the company had been notified by Cubist about the problem and was conducting its own investigation. "It's too early for us to say" if the pump was responsible for the chemical, Kirkpatrick said. All components used in manufacturing the pump are made either in the United States or Mexico, he added. One patient has called the company to complain about skin irritation after using the ReadyMed pump, which brings in less than $10 million in annual revenue, Kirkpatrick said. Cubist has said it expects Cubicin to bring in up to $385 million in U.S. sales in 2008 and the company does not expect that to change. "We think there may be an inconvenience certainly to customers ... but we don't expect it to impact our business," Cubist's McIntyre said. Use of the antibiotic with the ReadyMed pump represents about 2 to 3 percent of the drug's use, she said. MBT was found in reconstituted Cubicin stored in Cardinal's ReadyMed elastomeric infusion pumps but not I-Flow Corp's <IFLO.O> Eclipse pump, which was also tested, McIntyre said. Patients can also use Baxter International Inc's <BAX.N> Intermate pump. Shares of Cubist fell 2.9 percent, or 58 cents, to close at $19.53 on the Nasdaq on Wednesday, while Cardinal shares closed down more than 1 percent, or 61 cents, at $53.26 on the New York Stock Exchange. Shares of I-Flow closed down 2.7 percent, or 35 cents, at $12.81, also on the Nasdaq. A copy of the FDA letter is online at http://www.fda.gov/medwatch/safety/2008/cubicin_DHCP.pdf (Additional reporting by Lisa Richwine; Editing by Brian Moss and Braden Reddall)
A Mexican soldier stands guard on a street in Ciudad Juarez, Mexico April 4, 2008. Hundreds of camouflage-clad Mexican troops patrol in Ciudad Juarez to quell a surge in drug gang ...
