Reply To: Methadone and the Sphincter of Oddi
This is an interesting question that much better developed in human medicine:
The most common functional disorder of the biliary tract and pancreas relates to the activity of the Sphincter of Oddi. The Sphincter of Oddi is a small smooth muscle sphincter strategically placed at the junction of the bile duct, pancreatic duct, and duodenum. The sphincter controls flow of bile and pancreatic juices into the duodenum and prevents reflux of duodenal content into the ducts. Disorder in its motility is called Sphincter of Oddi dysfunction. Clinically this presents either with recurrent abdominal biliary type pain or episodes of recurrent pancreatitis. Most of these patients present with abdominal pain. Symptomatic treatment comprises treatment of abdominal pain. In patients with a severe episode of either biliary or pancreatic Sphincter of Oddi dysfunction the most appropriate pain medication is parenteral opiates. This is despite the known observation that opiates produce sphincter of Oddi contraction. The rational for their use is that the contraction has already occurred and the opiate is unlikely to aggravate matters further. However, on the other hand opiates are the most effective therapy for pain relief. In order to prevent future episodes in patients who have identified opiates such as codeine to provoke pain avoidance of these medications is recommended. There is no effective pharmaceutical therapy for these patients.
Reflecting on that, I would not withhold methadone/full opioids in cases of abdominal pain. If the rationale is that we are preventing Sphincter of Oddi contraction, it has probably already happened in these cases. In cases of known pancreatitis we would still use opioids, as further contraction will not worsen signs.
The only thing that we may have to be cautious of is long term opioid use, which is not really a thing for our patients:
Hope that helps!