Opioid receptor signaling: relevance for gastrointestinal therapy.

Opiate drugs, such as morphine, are renowned for their analgesic properties. To date, opioid narcotics represent the largest and most potent class of pain relievers available to treat both acute and chronic pain conditions. The use of opiates, however, is severely limited by several adverse side effects. Upon chronic use, opiates can produce tolerance, physical dependence and addiction. Although these conditions warrant consideration, there are acute effects that present more immediate concerns when choosing opiate narcotics for pain therapy. One of the most prevalent side effects, which continues for as long as the opiate is used for pain control, is constipation. This can impact patient compliance, as it is often one of the top reasons why patients discontinue opiate treatment. The challenge, therefore, is to develop pain therapies that preserve potent analgesia while preventing constipation.