Many of the studies that raised the risk were done by Dr. Peter C. Butler, chief of the division of endocrinology at the University of California, Los Angeles. In an email Wednesday, Dr. Butler, who has been hailed as a hero by his backers and assailed as a zealot by critics, said the commentary “provides very little information as to how they reached this conclusion.” He called for the analyses to be made public for independent scrutiny.

Dr. Sidney M. Wolfe, founder and senior adviser to the Public Citizen Health Research Group, which has petitioned the F.D.A. to remove Victoza from the market, was also critical of the F.D.A.’s conclusions, saying, “I don’t know what purposes are served by giving false assurances of safety.”

The European agency had already said last July that it did not see much cause for concern and the F.D.A. had said it basically agreed with that, though it was still investigating. This is the first time, however, that the F.D.A. is offering a detailed written explanation of its conclusions.

Dr. Amy G. Egan, an F.D.A. official and the first author of the article, said she was not aware of another instance in which European and American regulators had jointly published conclusions in a medical journal. She said in an email that because of the “intense interest” in the issue, the agencies had been sharing their reviews and findings, and decided “that a joint publication would best convey this consensus of opinion.”

The officials cautioned that they had not reached a final conclusion and would continue to gather more data. They said, however, that “the totality of the data that have been reviewed provides reassurance.” They said pancreatitis, an inflammation of the pancreas, is considered a risk with the drugs but one that is already adequately reflected in the labels.