Placebo effect in the treatment of duodenal ulcer

Aims To assess whether frequency of placebo administration is associated wi th duodenal ulcer healing. Methods A systematic literature review of randomized clinical trials was un dertaken. 79 of 80 trials that met the inclusion criteria. The pooled 4 wee k placebo healing rate of all duodenal ulcer trials that employed a four ti mes a day regimen was compared with the rate obtained from trials with a tw ice a day regimen. Results The pooled 4 week healing rate of the 51 trials with a four times a day regimen was 44.2% (805 of 1821 patients) compared with 36.2% (545 of 1 504 patients) in the 28 trials with a twice a day regimen (difference, 8.0% [equal effects model]; 95% confidence interval, 4.6% to 11.3%). Depending on the statistical analysis, the rate difference ranged from 6.0% (multivar iable random effects model) to 8.0% (equal effects model). A number of sens itivity analyses showed comparable differences between the two regimens. Mo st of these sensitivity analyses were not significant, probably because a n umber of trials were excluded resulting in a loss of power. Conclusions We found a relation between frequency of placebo administration and healing of duodenal ulcer. We realize that the comparison was based on nonrandomized data. However, we speculate that the difference between regi mens was induced by the difference in frequency of placebo administration. A better knowledge of various placebo effects is required in order to make clinically relevant assessments of treatment effects derived from placebo-c ontrolled trials.