US regulators on Tuesday published a long-awaited study that estimated Merck's painkiller Vioxx, withdrawn from the market in September, could have caused 27,785 heart attacks or deaths since it was approved in 1999.

The study, sponsored by the US Food and Drug Administration, also attacked Merck and its efforts to explain away signs in company-sponsored clinical trials four years ago that showed Vioxx increased the risk of heart attacks.