Effects of pharmacological agents on gastrointestinal motility

The control mechanisms of gastrointestinal motility are complex. Extrinsic neurohormonal effects modulate an intrinsic system, often called the "gut brain," composed of nervous and neuropeptide components. To exert pharmacologic influence on GI motility, use is made of agents that mimic the external control system. Agents that stimulate opioid receptors, block adrenoceptors, block or facilitate acetylcholine action, or antagonize the action of prostaglandins are used to effect changes in GI motility. The major indications for pharmacologic intervention are to increase motility in constipation, to reduce it in most cases of diarrhea, and to restore propulsive coordination in postoperative ileus. In cases of clinical colic the primary requirement is control of pain. Agents used for this purpose may adversely affect motility, and choice requires knowledge of their actions in this respect. In addition, drugs used for other purposes, anthelmintics for instance, may also influence gut motility. A synopsis of the actions of the agents commonly employed in GI motility control and some associated drugs are displayed in Table 3. Recent advances in the understanding of drug action on the gut should help in the selection of drugs for clinical use.