The U.S.-based Boston Scientific Corp. has admitted there is an increased risk of blood clots caused by use of its drug-coated cardiac stent.

The company -- the leading stent seller in the nation -- says an analysis of clinical data reveals the increased risk of blood clots months after a stent is implanted, The Wall Street Journal reported, noting the announcement marks the first time any stent maker has acknowledged the heightened risk of side effects from using drug-coated stents.

Stents are small, wire-mesh tubes that are inserted into a blood vessel or other body structure to provide support and keep the structure open. The drugs used to coat some stents are designed to prevent growth of tissue after implantation.

The Journal said stent sales exceed $5 billion annually in a market dominated by Boston Scientific and Johnson & Johnson.

Boston Scientific, which has its headquarters in Natick, Mass., claims recent studies suggest both its Taxus brand of stent and J&J's Cypher stent present similar risks of late-occurring blood clots. J&J company officials, however, told the Journal they see no statistically significant risk of late thrombosis caused by their Cypher stents.

Copyright 2006 by United Press International