Gender and the placebo analgesic effect in acute pain

Objective: Our objective was to examine the placebo arms from a series of c linical trials in which the post-third molar extraction dental pain model w as used to elucidate the time course of the placebo effect and the proporti on of the population that are responders, as well as to evaluate whether th e placebo analgesic response of female subjects may differ from that of mal e subjects. Methods: We performed a meta-analysis of 596 subjects included in the place bo treatment arm of 16 double-blind, post-third molar extraction dental pai n (moderate to severe) studies submitted to the Food and Drug Administratio n electronically. The inclusion and exclusion criteria were practically ide ntical in all studies. Pain relief and pain intensity measurements used the same metrics in all studies. The measurements were recorded just before dr ug administration and at least at postdose hours 0.5, 1, 1.5, 2, 3, 4, 5, a nd 6. Results: There were325 female subjects and 271 male subjects. They were all otherwise healthy; with a mean age of 21.6 years for female subjects and 2 2.3 years for male subjects. The postoperative baseline pain was greater in female subjects than in male subjects, and this difference was statistical ly significant. Both pain intensity and pain relief scores demonstrate the well-established placebo effect in 10% of the pooled subjects, as well as i n all the individual studies: Over time, however, the mean pain intensity a nd pain relief scores for the female and male treatment groups were not not iceably different at any time point after medication. Further analysis of t he data showed no gender difference in duration of action of the placebo. Conclusions: The results demonstrated no gender difference in response to p lacebo. These results were obtained from the post-third molar extraction si tuation, in which the least possible confounding factors were present. To f ully establish the generality of this phenomenon, studies should be carried out in other pain models.