New evidence shows that the drug makers Merck and Schering-Plough have conducted several studies of their popular cholesterol medicine Zetia that raise questions about its risks to the liver, but the companies have never published those results.
Partial results of the studies, alluded to in documents on the Food and Drug Administration’s Web site, raise questions about whether Zetia can cause liver damage when used long term with other cholesterol drugs called statins.
Most of the millions of people who use Zetia take it along with a statin like Lipitor, Crestor or Zocor. Or they take it in a single pill, Vytorin, that combines Zetia with Zocor.
The discovery of the unpublished research comes as Merck and Schering are already under criticism for not yet releasing data from an important Zetia study, called ENHANCE, that they completed early last year.
The Enhance data may also contain important information about Zetia’s liver risks. At least some patients were dropped from the Enhance study after testing revealed that they had elevated liver enzymes, a Schering-Plough spokesman confirmed this week.
But a full report on that trial, including the number of patients who had liver problems, will not be available until March.
Doctors say that by failing to disclose promptly all their research, Merck and Schering-Plough may be leaving the public with a misleadingly favorable view of Zetia’s safety and benefits.
“You don’t want to have data missing,” said Dr. Bruce Psaty, a professor of medicine and epidemiology at the University of Washington. “When there have been adverse effects, when the benefits don’t look impressive, those are the trials that historically don’t make it to press.”
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