Background & aims: Although widely prescribed, the evidence for the use of antidepressants for the treatment of irritable bowel syndrome (IBS) is limited. In this study, we hypothesized that fluoxetine (Prozac), a selective serotonin reuptake inhibitor, has visceral analgesic properties, leading to increased sensory thresholds during rectal distention and improvement of symptoms, in particular in IBS patients with visceral hypersensitivity.
Methods: Forty non-depressed IBS patients underwent a rectal barostat study to assess the sensitivity to rectal distention before and after 6 weeks of treatment with fluoxetine 20 mg or placebo. Abdominal pain scores, individual gastrointestinal symptoms, global symptom relief, and psychologic symptoms were assessed before and after the intervention.
Results: At baseline, 21 of 40 patients showed hypersensitivity to rectal distention. Fluoxetine did not significantly alter the threshold for discomfort/pain relative to placebo, either in hypersensitive (19 +/- 3 vs. 22 +/- 2 mm Hg above MDP) or in normosensitive (34 +/- 2 vs. 39 +/- 4 mm Hg above MDP) IBS patients. Overall, 53% of fluoxetine-treated patients and 76% of placebo-treated patients reported significant abdominal pain scores after 6 weeks (not significant). In contrast, in hypersensitive patients only, fluoxetine significantly reduced the number of patients reporting significant abdominal pain. Gastrointestinal symptoms, global symptom relief, and psychologic symptoms were not altered.
Conclusions: Fluoxetine does not change rectal sensitivity in IBS patients. Possible beneficial effects on pain perception need to be confirmed in larger trials.