In the 1970’s, the Food and Drug Administration adopted a laboratory test for acid neutralizing capacity (“ANC”) which defines OTC antacids for purposes of labeling and measures their strength. The test determines how much acid is neutralized in a glass beaker by a single dose of antacid over a fifteen-minute period. The ANC test does not measure an antacid’s capacity to neutralize acid in vivo, which depends on other factors in addition to ANC,3 nor does it provide information on an antacid’s ability to relieve the symptoms of acid indigestion. Such information would be more useful to consumers than the results of laboratory studies, but the FDA concluded human testing would be too laborious. ANC information is provided to physicians, but because the FDA thought the consuming public might mistakenly take the ANC rating as a measure of effectiveness, it decided to exclude such information from product labels. It concluded that this “technical information on the consumer label could result more in confusion than enlightenment and could result in unwarranted consumer reliance solely upon this information as an indication of relative effectiveness.” 38 Fed.Reg. 31264 (11/12/73). Ironically, the very information the FDA feared would mislead consumers has become the basis of advertising claims and is called upon to support such claims when they are challenged as false or misleading.