Determinants of response to anorexiants.

We analyzed data from an 81-patient clinical trial of anorexiant medication, searching for the predictors of response. In the trial we assigned treatments to participants by minimization, a process that decreases differences between treatment groups. Based on the literature, the investigators' experience, and the pharmacologic properties of the medications, we selected 25 factors for use in the minimization process. Retrospective examination by contingency-table analysis indicated that the most important predictors of weight loss in this study were weight loss during the 3-wk diet-only run-in period (chi 2, p less than 0.001), physician estimation of patients motivation (chi 2, P less than 0.003), participant eating habits (nighttime "binge" eaters responded best; chi 2, P less than 0.003), adherence to treatment (chi 2, P less than 0.01), and type of treatment (chi 2, P = 0.05). When multiple regression analysis was applied, several other factors aided in explaining the variance in the weight loss results. For example, duration of obesity was inversely related to weight loss and weight loss during the study increased with family income. Depending on the treatment used, anxiety and depression visual analogue scores also explained some of the variance. Failure to account for factors such as these in treatment assignment may account for the low discriminant power of clinical trials of anorexiants.