Some Implications of the Double-Blind Format in Evaluating Drug Efficacy: Studies of the Appetite Suppressant Phenylpropanolamine

It is hypothesized that the weight loss effected by phenylpropano-lamine (PPA) is a function of whether the product is taken as part of a double-blind placebo-control comparison, a double-blind comparison between PPA and an active substance, or by persons purchasing and using it on their own in the community. In a series of studies, the hypothesis was confirmed, with a statistically significant weight loss ratio of 1.00:1.28:2.81 among the three modalities. Some reasons for the greater weight loss experienced by users in the community over those in the two double-blind studies are discussed. Some implications of the findings in terms of the design employed for assessing drug efficacy are noted.