On September 17, 2001, the FDA issued a warning letter on Merck's marketing of Vioxx. Does this demonstrate liability is appropriate?
Not when read in the appropriate context.
When faced with a violation, the FDA has discretion for engaging in an enforcement action or issuing a "warning letter" for a "minor violation." See 21 U.S.C. § 336. This is an unreviewable decision of prosecutorial discretion. See Heckler v. Chaney, 470 U.S. 821, 837-38 (1985). The FDA is very strict about what pharmaceutical companies can say, sometimes even penalizing them for prematurely repeating scientifically-true facts that are published in medical journals before the FDA signs off on the principle. If plaintiffs are allowed to seek civil damages on the basis of a warning letter, which was issued because Merck committed only a minor violation, it completely disrupts the entire regulatory structure. "This flexibility is a critical component of the statutory and regulatory framework under which the FDA pursues difficult (and often competing) objectives." Buckman v. Plaintiffs Committee, 531 U.S. 341, 349 (2001).
The letter further demonstrates that there is no failure-to-warn problem: Merck was required to send a "Dear Healthcare Provider" letter (p. 7) and did so in April 2002. Doctors knew everything Merck did about the possibility of pro-thrombotic risk. The claim that Merck hid something is a claim that Merck had perfect foresight that it did not share.