Low doses of the antidepressant amitriptyline seem to be effective in relieving the symptoms of Irritable bowel syndrome (IBS), according to the results of a small study.

Brain imaging has shown unusual activity in an area called the anterior cingulate cortex, “an area relevant to pain and emotions,” during painful rectal distension in people with IBS, Dr. H. Mertz and colleagues from Vanderbilt University, Nashville, Tennessee, write in the medical journal Gut.

The researchers looked into whether low-dose amitriptyline reduced this activation of the anterior cingulate cortex. Also, because stress appears to be an important IBS trigger, the team examined the effects of amitriptyline during mental stress.

Nineteen participants with IBS were randomly assigned to take amitriptyline or an inactive placebo for a month. Then, after a 3-week “washout” period, the subjects crossed over to the alternate treatment.

Thirteen patients reported improved symptoms on amitriptyline and five reported improved symptoms on placebo. One patient reported no change on either treatment.

Patient ratings of pain during the last 2 weeks of treatment were 4.2 on amitriptyline and 5.3 on placebo.

Reduced pain-related activation in the anterior cingulate cortex was observed with amitriptyline treatment, and this effect was greater during stress.

“We postulate that amitriptyline improves symptoms in IBS due to a central nervous system effect rather than a peripheral one,” the investigators write. They say the drug may work by reducing the perception of pain, or by a reduction in stress-related aggravation of symptoms.

SOURCE: Gut, May 2005.