CNBC's Huckman: More Questions Arise on Drug-Coated Stents

Two studies and an editorial in the journal of the American Medical Association are raising even more questions about the safety of drug-coated stents and could further hurt already-declining sales.

This concerns so-called "off-label" use of drug-coated stents, which actually makes up the majority of procedures. It involves people who are in the throes of a heart attack, have big, multiple blockages or other medical complications.

Researchers say after one year, those patients had double the risk of death versus those who were treated "on-label" or have just one blocked artery.

And one of the studies says it only saw that problem with Boston Scientific's stent and not Johnson & Johnson's, though J&J paid for that study.

The JAMA editorial says doctors shouldn't "succumb to the hope and hype" of drug-coated stents. In fact safety issues and other new studies have led more doctors to switch back to bare metal stents or old-fashioned heart drugs.

J&J and Boston Scientific make the only drug-coated stents on the U.S. market. But Medtronic and Abbott hope to come to market here soon.