Assessment of the effects of phenylpropanolamine on appetite and food intake.

Single 37.5 mg doses of phenylpropanolamine (PPA) were given on each of two separate, nonconsecutive days to each of twelve nonobese women. PPA's effects on reported appetite and food intake were compared to those of a placebo also given on two nonconsecutive days. To control for possible effects on appetitive behavior of knowledge about the drug's putative role as an appetite suppressant, the subjects were told that PPA was a nasal decongestant which was expected to affect their sensitivity to flavors. Hunger rating before eating was significantly lower on trials after PPA than on trials after placebo (carry-over effect), but the direct effect of PPA on hunger was not significant. Although food intake was 26 g less under the PPA condition (407 g) than under placebo (433 g), this difference was not significant. However, because of insufficient power, the null hypothesis could not be accepted. The true effect of PPA on intake remains inconclusive. Either more subjects must be tested at this dose or the effect must be made larger by changing the dose, in order to obtain conclusive results.