Placebo in functional dyspepsia: Symptomatic, gastrointestinal motor, and gastric sensorial responses

Objective: Therapeutic trials in functional dyspepsia consistently show a s ubstantial placebo response, but there is no clear explanation for such an effect. Our aim was to evaluate symptomatic, gastrointestinal motor, and ga stric sensorial responses to placebo treatment in patients with chronic and severe functional dyspepsia who were part of a therapeutic trial. Methods: Thirty patients mere treated during 8 wk with placebo (white-colored 8-mm tablets containing cellulose) by mouth, 20 min before breakfast, lunch, and dinner. We quantified the symptomatic response to placebo as a change in g lobal health status, and also as a change in the individual and combined (g lobal symptom index) of a five-symptom complex: upper abdominal pain, nause a, vomiting, bloating/fullness, and early satiety. Gastroduodenal motility, during fasting and postprandially, was evaluated by manometry in all patie nts pretreatment and in 17 patients posttreatment. Gastric sensitivity to d istension was evaluated in 18 patients pretreatment and in five patients po sttreatment (all of them clinical responders). Results: Placebo treatment p roduced a striking symptomatic improvement; by 8 wk 80% of the patients rep orted an improved global health status and their global symptom index marke dly decreased (23.9 +/- 1.3 pretreatment vs 9.1 +/- 1.2; p < 0.05). Placebo increased the number of gastric phases III starting in the antrum during t he fasting period (1.1 +/- 0.1 vs 1.6 +/- 0.2; p < 0.05). As a group, no si gnificant changes in posaprandial gastroduodenal motility were observed aft er placebo treatment. However, after placebo a significant improvement in t he antral motility index (MI) was observed in the subset of patients with a ntral hypomotility (MI pretreatment: 7.9 +/- 1.0; MI posttreatment: 11.7 +/ - 0.4; p < 0.05). Before placebo treatment, patients with functional dyspep sia showed increased sensitivity to stepwise distension of the stomach rela tive to healthy individuals. After 8 wk of placebo treatment sensitivity to distension remained unchanged, even though patients' clinical status was m arkedly improved. Conclusion: In patients with functional dyspepsia, the sy mptomatic response to placebo is substantial. Some significant changes were also observed in gastric motility: increase in the gastric phase III numbe r as well as in the postprandial antral motility index in those with hypomo tility pretreatment. Remarkably, however, clinical improvement seems to occ ur independently of detectable changes in gastroduodenal motor activity or gastric hypersensitivity to distension. (C) 1999 by Am. Coll. of Gastroente rology.