An investigation of drug expectancy as a function of capsule color and size and preparation form.

Much of a drug response is related to nonspecific factors. Perceptual characteristics of drug preparations likely play a major role in expectancy and response. This study focused on perceptual characteristics of a preparation related to anticipated effect: capsule color, capsule size, and preparation form (capsule versus tablet). College students ranked capsules for perceived strength based on capsule size, categorized capsules in terms of anticipated pharmacological effect based on color, and evaluated strength based on preparation form. Data showed nonchance distributions for nine capsule colors in anticipated action, with specific effects for four colors. A significant difference between capsule and tablet for perceived strength was found, as was a trend relating capsule size to perceived drug strength. Discussion centered on awareness and consideration of drug perceptual characteristics in support of drug efficacy.