Elsevier

The Journal of Pain

Volume 7, Issue 1, January 2006, Pages 43-48
The Journal of Pain

Original report
Opioid Tolerance and Hyperalgesia in Chronic Pain Patients After One Month of Oral Morphine Therapy: A Preliminary Prospective Study

https://doi.org/10.1016/j.jpain.2005.08.001Get rights and content
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Abstract

There is accumulating evidence that opioid therapy might not only be associated with the development of tolerance but also with an increased sensitivity to pain, a condition referred to as opioid-induced hyperalgesia (OIH). However, there are no prospective studies documenting the development of opioid tolerance or OIH in patients with chronic pain. This preliminary study in 6 patients with chronic low back pain prospectively evaluated the development of tolerance and OIH. Patients were assessed before and 1 month after initiating oral morphine therapy. The cold pressor test and experimental heat pain were used to measure pain sensitivity before and during a target-controlled infusion with the short-acting μ opioid agonist remifentanil. In the cold pressor test, all patients became hyperalgesic as well as tolerant after 1 month of oral morphine therapy. In a model of heat pain, patients exhibited no hyperalgesia, although tolerance could not be evaluated. These results provide the first prospective evidence for the development of analgesic tolerance and OIH by using experimental pain in patients with chronic back pain. This study also validated methodology for prospectively studying these phenomena in larger populations of pain patients.

Perspective

Experimental evidence suggests that opioid tolerance and opioid-induced hyperalgesia might limit the clinical utility of opioids in controlling chronic pain. This study validates a pharmacologic approach to study these phenomena prospectively in chronic pain patients and suggests that both conditions do occur within 1 month of initiating opioid therapy.

Key words

Tolerance
hyperalgesia
chronic pain
opioid
morphine

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Supported by a research fellowship grant from the Foundation for Anesthesia Education and Research.