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Why oral opioids may not be effective in a subset of chronic pain patients

PainSci » bibliography » Tennant 2016
Tags: medications, self-treatment, treatment

Three articles on PainSci cite Tennant 2016: 1. The Complete Guide to Trigger Points & Myofascial Pain2. Complete Guide to Frozen Shoulder3. Opioids for Chronic Aches & Pains

PainSci commentary on Tennant 2016: ?This page is one of thousands in the bibliography. It is not a general article: it is focused on a single scientific paper, and it may provide only just enough context for the summary to make sense. Links to other papers and more general information are provided wherever possible.

We tend to think of opioids as potent drugs that are going to make pretty much anyone high, and therefore probably provide some pain relief … but there’s an incredible range of responses to drugs, even strong ones. This paper presents some specific reasons why some people just aren’t much affected by (oral) opioids: “there is a group of intractable pain patients who do not effectively metabolize oral opioids,” mainly because of gastrointestinal disorders and an inherited metabolic problem (cytochrome P450 enzymatic defects).

~ Paul Ingraham

original abstract Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.

OBJECTIVE: To identify possible underlying causes of poor oral opioid effectiveness.

METHODS: Ninety-five (95) adults who were referred for evaluation and medical management of their intractable pain were screened to determine if oral opioids provided enough pain relief to physically and mentally function and carry out activities of daily living. A clinical evaluation included history, physical examination, cytochrome P450 enzyme testing and a hydromorphone injection to help confirm lack of oral opioid effectiveness.

RESULTS: Twenty (20; 21.1%) of the 95 patients reported that three or more oral opioids had not provided enough pain relief to allow them to mentally and physically function and carry out activities of daily living. Patients all reported some typical symptoms of malabsorption including nausea and steatorrhea, and 14 (70.0%) reported that they had observed undigested medication in their stools. Fifteen (15; 75.0%) had experienced pain relief with an injectable opioid. Two major causes for lack of oral opioid effectiveness were apparent: (1) gastrointestinal disorder (11; 55.0%) and (2) cytochrome P450 enzymatic defects (9; 45.0%). In addition to these basic causes, a number of other possible contributing factors were identified which included abdominal, pelvic and spine surgeries, traumatic brain and neck injury, and autoimmune disorders.

CONCLUSIONS: There is a group of intractable pain patients who do not effectively metabolize oral opioids. Although gastrointestinal disease and cytochrome P450 enzymatic defects appeared to be dominant causes of oral opioid ineffectiveness, there were other possible contributing factors such as abdominal, pelvic and spine surgeries, head and neck trauma, and autoimmune disease. Pain patients who report poor oral opioid effectiveness should be evaluated for the presence of underlying pathologic conditions which may interfere with oral opioid metabolism and, if found, be considered for nonoral opioid treatment.

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