Treatment Options for Irritable Bowel Syndrome (IBS)

In long term management of Irritable Bowel Syndrome (IBS), diet is more important than medication. You need adequate fiber to maintain a soft, formed, moist, preferably daily bowel movement. Inadequate bowel motility causes constipated stool that irritates the bowel wall and causes colon spasms. Eating too large a meal (especially a fatty meal) causes spasms of the colon via the gastro colic reflex. Some people are intolerant of certain foods – milk products, wheat, and lettuce are common examples. Of course, good sleep, physical fitness and general stress management are essential to the management of IBS.
Muscle in the intestine is controlled by the autonomic nervous system and therefore doesn’t respond to the same relaxants as skeletal muscle. Some antidepressants – Paxil of the SSRI’s and the tricyclics have relaxation of the intestines as a potential side effect by blocking the parasympathetic system. Paxil may help IBS with predominantly diarrhea. Zoloft is more stimulating to the intestine and might help IBS with constipation. Medications that increase norepinephrine (Effexor, Cymbalta, and Wellbutrin) can also decrease intestinal bowel activity by activating the sympathetic nervous system. Both of these effects can decrease the spasms associated with IBS.
Intestinal muscle is especially sensitive to serotonin and medications that block a certain serotonin receptor (5HT3) are strong intestinal wall relaxants (Lotrinex and Zofran). Conversely IBS with predominantly constipation responds to the more recently available stimulant of a particular serotonin receptor (5HT4) called Zelnorm. Opiods Lomotil (Imodium) at the milder level, and Paregoric at the strongest level are powerful relaxants that are sometimes used for severe spasms of the colon. Anticholinergics (especially Levsin) work better for stomach spasms but have some relaxant effects for spasms of the colon. Levsin has the advantage of coming in a quickly acting sublingual (under the tongue) tablet.
Benzodiazepines that reduce general arousal and anxiety have an indirect effect on gastrointestinal muscle. The only one that may have more direct relaxant effect would be Klonopin (clonazepam) since it is the one that decreases serotonin release. Xanax is better for depression. Klonopin is best for obsessing and especially racing thoughts.