Embedded Player Merck documents show that in 2000, the maker of Vioxx tried to censor critics of the drug's safety. That was the year that drug giant Merck learned that Vioxx might cause heart attacks and other problems. The documents show a concerted effort by the company to identify doctors who were raising questions about the drug's safety and to put pressure on them to stop making critical comments. A spokesman for Merck denies the allegations.