BERKELEY, CA (UroToday Inc.) - The placebo response in trials for stress urinary incontinence (SUI) can be quite marked. It can range anywhere from 27% to as high as 75%. This phenomenon is seen in both pharmaceutical as well as sham pelvic floor muscle training (PFMT). It is not clear if there are underlying factors which may affect the placebo response. Yalcin and

Bump from the Lilly Research Laboratories in Indianapolis, Indiana sought to describe the effects of previous treatment for SUI and initial severity of incontinence on the subsequent placebo response to therapy in women with SUI.

They analyzed data from four double blind, placebo-controlled, randomized, multinational studies that compared duloxetine treatment to placebo therapy. Subjects all had dominant symptoms of SUI and a minimum of four incontinence episodes per week. At baseline, subjects reported any previous continence interventions including PFMT and surgery. Incontinence episode frequency (IEF) was the primary measure in all the trials and was recorded by completing voiding diaries on at least three days, one week prior to baseline visit and at three times during the treatment phase of the study. IEF was then compared to baseline and broken into subgroups: severity of incontinence (IEF <14 or IEF =14), current use of PFMT and presence or absence of previous continence surgery.

They reported their results in the July 2004 edition of the American Journal of Obstetrics and Gynecology. A total of 1913 women were randomized to receive duloxetine (958 subjects) or placebo (955 subjects). When the placebo group was analyzed, the mean baseline IEF was 17. They then showed an overall 33 % median decrease in IEF after treatment. The placebo group also had 55.5% with an IEF = 14, 16.5% who were currently using PFMT and 11.5% who had previous continence surgery. The median percent decrease in IEF in the placebo group was lower in women with more severe SUI, those who had previous continence surgery, and those undergoing PFMT. However, only the PFMT group was statistically different.

This study demonstrates that the measurable placebo response for SUI can be influenced by pretreatment variables and must be considered when planning a study or reviewing data from such studies.

Am J Obstet Gynecol 2004; 191:194-7