Zelnorm Deemed Safe for IBS Constipation
Watchdog Group Still Worried, but GI Docs Happy
Editor's Note: In March 2007 the FDA asked Novartis -- the maker of
Zelnorm -- to pull the drug from the market because of evidence that it raises
the risk of heart attacks and stroke. But in July 2007 the FDA ruled that
Zelnorm may be used by some patients in critical need of the drug who do not
have heart problems.
Oct. 29, 2002 -- Zelnorm is safe for at least 12 months of use,
say doctors who tested the newly approved drug for the constipating form of
irritable bowel syndrome (IBS). But not everyone agrees.
Zelnorm -- known as Zelmac in Europe -- traveled a rocky road
on its way to U.S. approval. Concerns that the drug might cause gallbladder
problems held up approval for a year. Those fears proved groundless, experts
However, the consumer watchdog group Public Citizen
unsuccessfully petitioned the FDA to deny approval. It says the drug's small
benefit in clinical trials doesn't justify the risk of possible side effects.
And the group points to evidence that ovarian cysts -- sometimes requiring
surgery -- could be a rare but serious Zelnorm side effect.
One reason for concern is recent history. Zelnorm affects the
serotonin system, a complex series of chemical signals that keep the body in
synch. Two other digestive system drugs that affect this same pathway system
recently ran into problems. Propulsid was taken off the market when it turned
out to harm the heart. And Lotronex, a drug for IBS diarrhea, can cause
So there's lots of interest in a new study that followed 579
patients who were supposed to take Zelnorm for one year. About half of them
stopped taking it, but only a few stopped because of side effects. Those who
kept taking the drug had very few problems. One patient did develop an ovarian
cyst, but lead researcher Gervais Tougas, MD, says it appeared unrelated to the
medication. Tougas is director of the gastrointestinal motility laboratory and
chief of gastrointestinal Services at St. Joseph's Hospital in Hamilton,
Ontario. His study appears in the current issue of Alimentary Pharmacology
"There is nothing in these data to support the idea that
this [ovarian cyst] is a signal that such problems happen with increased
frequency in [people who take] Zelnorm," Tougas tells WebMD.
The data show nothing because the study was poorly designed,
counters pharmacologist Elizabeth Barbehenn, PhD. Barbehenn is a former FDA
scientist who now serves as a research analyst for Public Citizen.
"It's a big joke," Barbehenn tells WebMD. "There
was no control group, so you could say anything you want. Half the people
dropped out before the study ended. And there was no protocol for whether the
drug caused problems. They let the investigators just decide whether they
thought adverse events were related to the drug."