What is the role of antidepressants in IBS?
Antidepressants are commonly used for moderate to severe abdominal symptoms associated with IBS. TCA medications are the most commonly used antidepressants for IBS symptoms. Typically the TCAs are administered in low doses (e.g., between 10-50 mg). The exact mechanism of action is not clear, but includes visceral analgesia, improvement in sleep, and normalization of the GI transit. Their effects in IBS appear to be independent of the TCAs’ effects on depression or other psychological parameters. Data on the efficacy of TCAs in patients with IBS are inconsistent. However, in the largest published randomized, placebo-controlled trial to date, desipramine (escalating dose from 50 to 150 mg) was not superior to placebo in intention-to-treat analyses but in a per protocol analysis limited to patients with detectable plasma levels of desipramine showed a significant benefit over placebo.
Several small trials suggest that SSRIs may have beneficial effects in patients with IBS. These effects appear to be mostly limited to improvement in well-being and less so in abdominal pain. SSRIs may be particularly beneficial for patients with concomitant psychological disorders such as anxiety, panic, and depression. Because serotonin is associated with diarrhea, SSRIs may be better tolerated in IBS-C. SSRIs have been associated with agitation, nausea, and sleep disturbance, among other side effects.