This study points out the sometimes unusual dose response curves which prompts the old saying, the dose makes the poison. And people's individual metabolism varies quite a bit.
Few would have guessed a result such as in this study, 1mg/kg of ethanol in mice improved memory recall, for example. This would equate to around a quarter to a half of a normal drink in adults.
A review of the literature indicates that, for several drugs and chemicals, the effects of nanogram doses are the opposite of the effects of milligrams, because different doses have different sites as well as mechanisms of actions. In conclusion, from the above results one may suggest that, in determination of the dose-response of at least some drugs, the study of the effects of doses much lower than two orders of magnitude of the minimum effective dose are warranted.