A few weeks ago, a long-awaited study known as the Victor trial was published in The New England Journal of Medicine about Vioxx and colorectal cancer. The findings were contentious, however, because they suggested the painkiller may have caused heart attacks far sooner than Merck indicated. And buried in the methodology section was something else of interest.

The authors, led by Oxford University’s David Kerr, wrote that paperwork given trial participants was “amended twice to reflect evolving data on the possible adverse cardiovascular effects” associated with Vioxx. The statement apparently refers to the ongoing debate over Vioxx and heart risks, which took place while the trial was conducted between 2002 and September 2004, when Vioxx was withdrawn.

However, the patient information sheets didn’t include any reference to cardiovascular risk. This is the 2002 form, and this is the 2004 form.

This is an issue for a couple of reasons. For Merck, this omission may augur greater liability beyond the 27,000 or so product-liability lawsuits already filed in state and federal courts, because it raises questions about the extent to which the drugmaker was willing to acknowledge cardiovascular risks. On a broader plane, a failure to provide risk info is the sort of behavior that can undermine public confidence in the value of participating in clinical trials, which affects the entire medical community and the pharmaceutical industry at large.

“It’s an unacceptable omission,” says Art Caplan, who directs the Center for BioEthics at the University of Pennsylvania, after reviewing the forms. “There’s just nothing there, and there should have been some mention of the CV risk. When risk info isn’t there, people are being recruited under false pretenses. If people worry risks aren’t fully disclosed, they’ll be much more worried about participating.”

We wrote Kerr for an explanation, twice, but he never replied. A spokesman for Merck, Kent Jarrell, wrote us that the patient information sheets noted Vioxx may cause an “increase in blood pressure”; that patients with prior heart attacks were provided additional info (although it’s not clear what info or how or when it was transmitted) and that doctors had access to Vioxx product labeling at all times. But the drugmaker didn’t provide any documentation to support Kerr’s claims in the New England Journal article or assert that trial participants were, in fact, given additional paperwork at any time, despite repeated requests.

In fairness, the forms do indicate that patients were warned they may experience a “swollen tummy and wind.” In other words, Vioxx trial participants weren’t given a heads up that they may have been at risk for a heart attack, but they were cautioned the painkiller was likely to make them fart.