Clinical Question: Are selective serotonin reuptake inhibitors (SSRIs) effective for the treatment of irritable bowel syndrome (IBS)?

Setting: Outpatient (specialty)

Study Design: Randomized controlled trial (double-blinded)

Allocation: Concealed

Synopsis: Although tricyclic antidepressants are somewhat effective for the treatment of IBS, it is less clear whether SSRIs are similarly helpful. Patients in this study came from two groups: (1) those on a low-fiber diet who presented to a gastroenterologist and did not improve on a subsequent high-fiber diet; and (2) those already eating a high-fiber diet when they presented for care. The patients were randomized to treatment with placebo (n = 43) or paroxetine (n = 38) in a dosage of 10 mg per day, increased to 20 mg or 40 mg per day if there was no improvement at the lower dosage. The mean age of patients was 46 years, 74 percent were women, and most had diarrhea-predominant IBS. Eight patients withdrew from the paroxetine group, and seven withdrew from the placebo group; approximately one half of the patients in each group withdrew because of perceived adverse drug effects.

The primary outcome was overall well-being measured on a 5-point scale, in which an increase of 0.5 points signified a clinically significant improvement. (It was not clear whether the overall well-being score was part of the Irritable Bowel Syndrome Quality of Life or whether it was a separate, unvalidated scale.) A clinically significant improvement was reported by 63 percent of patients receiving fluoxetine compared with 26 percent receiving placebo (P = .01; number needed to treat [NNT] = 2.7). The benefit was similar for the subset of patients with a Beck Depression Inventory score of less than 10. Although a small improvement in food avoidance was noted for the patients taking paroxetine, there was no difference in work or social function. When patients were asked at the end of the 12-week study whether they wanted to continue the study medication, 84 percent in the paroxetine group said yes compared with 37 percent in the placebo group (P < .001; NNT = two). The mean improvement in scores for well-being was not reported.

Bottom Line: Paroxetine in a dosage of 10 to 40 mg per day provides at least a small benefit in terms of overall well-being for patients with IBS who already have tried a high-fiber diet. The true magnitude of this benefit is unclear because of the way the results in this study were reported. It also is unclear whether SSRIs are more effective than tricyclic antidepressants in patients with IBS. (Level of Evidence: 1b)