Long term opioid use can induce persistent pain as an automatic
adaptive response:
Because its main effect is mediated through the reward system, the brain
undergoes several adaptations in response to repeated opioid use. For
example, opioids can create pain as an adaptive counterbalancing effect
(opponent effect) to pain relief while the opioid dose is active.52,53,62-65 As this opponent effect grows with
continued long term opioid use, a broad physiological adaptation called
allostasis resets the baseline pain experience to higher set points
around which the pain/relief cycles fluctuate.52,53,65 Paired together, these phenomena are referred
to as allostatic opponent effect. 52,53,65 Disability
and suffering that includes anxiety, anger, irritability, depression,
concentration problems, sleep problems, fatigue, and lethargy can also
similarly increase as a part of the increasing allostatic opponent
effect. 52,53,65 The clinical experience of worsening
pain, suffering, disability, and overall health with psychiatric and
medical instability due to opioid induced allostatic opponent
adaptations may persist or worsen whether LTOT dose is continued,
increased, decreased or discontinued.52,65 When this
clinical picture emerges after discontinuation – also described as
protracted withdrawal/abstinence syndrome – it may persist and even
worsen for months or years after LTOT cessation or dose decrease due to
persistence of allostatic adaptations.52,65-68 More
detailed discussion of the allostatic opponent adaptations is provided
in Appendix 1.