3.2 Physical dependence and opioid withdrawal
In addition to tolerance and OIH, pain in patients with OUD can be
complicated by the consequences of physical dependence, namely opioid
withdrawal hyperalgesia89-91. Opioid withdrawal is
commonly assessed using standardized scales such as the Clinical Opiate
Withdrawal Scale (COWS)92, the Subjective Opioid
Withdrawal Scale93, and the Objective Opioid
Withdrawal Scale (OOWS)93. These tools evaluate
self-reported symptoms and observer-rated signs of opioid withdrawal,
including anxiety or irritability, perspiration or sweating, tearing or
lacrimation, runny nose or rhinorrhea, goosebumps or piloerection,
restlessness, as well as the presence of specific types of pain itself
(e.g., abdominal pain and cramps).
However, there is considerable overlap between the symptoms of opioid
withdrawal and those associated with poorly treated chronic pain. For
example, feelings of irritability94,
anxiety95, and restlessness96 can be
associated with chronic pain as well as opioid withdrawal. This
overlapping symptomatology makes it challenging to differentiate
etiology, potentially leading to inadequately treated pain in clinical
practice. Hence, clinicians must consider the possibility of
undertreated pain when evaluating opioid withdrawal, especially in
patients with known OUD. Figure 2 provides clinical pain
assessment parameters to distinguish between opioid hyperalgesia,
tolerance, and withdrawal. Such differential assessment can prevent
premature diagnostic closures that negatively affect pain-related
functioning.