Prokinetic agents are currently being investigated as potential
therapies for motility disorders of the lower gastrointestinal tract.
Cholinergic agonists such as
bethanechol are known to improve postoperative
ileus but are limited because of side effects.
Dopamine antagonists such as
domperidone appear to have maximal prokinetic effect in the proximal gastrointestinal tract and are effective for such conditions as
gastroparesis and
gastroesophageal reflux, but they appear to have little physiologic effect in the colon or in colonic motility disorders.
Naloxone, an
opioid antagonist, appears to hold promise in patients with
irritable bowel syndrome, small
intestinal pseudo-obstruction, and
constipation.
Erythromycin exerts its prokinetic effect by acting as a
motilin agonist; it has been used in the treatment of diabetic
gastroparesis and appears to improve symptoms of
colonic pseudo-obstruction and postoperative
ileus.
Metoclopramide, a combined
cholinergic agonist and
dopamine antagonist, is currently used exclusively for proximal motility dysfunction.
Cisapride appears to hold the most promise for patients with colonic motility disorders. In patients with postoperative
ileus,
cisapride is associated with an increased return of bowel function compared with placebo. In patients with chronic
constipation,
cisapride increases stool frequency and decreases
laxative abuse in both adults and children. Hopefully, as an understanding of gastrointestinal motility increases, effective prokinetic agents will be developed that will improve symptoms of patients with large bowel motility disorders and may also help to predict those patients who benefit from surgical management for
constipation.