Almost a dozen authors of a key study on the safety of Merck & Co.'s (MRK) arthritis medicine Vioxx Wednesday defended themselves from critics who claim the study excluded three heart attacks among patients who took the drug, which has since been withdrawn.

The authors, who are not affiliated with Merck, took issue with highly publicized allegations lodged in December by the New England Journal of Medicine against the so-called VIGOR study.

"We stand by our original article," the authors said, adding they do not believe the study needs to be corrected to include the heart attacks, as had been demanded by the Journal.

"We believe it is important to emphasize that Merck consistently made full and appropriate disclosures of the cardiovascular results from VIGOR," Merck officials said in an accompanying letter to the editor of the medical Journal on Wednesday.