Table 1.

Differential opioid dosing regimens and opioid-induced hyperalgesia

Condition	Pain and diagnostic symptoms	Onset	Response to opioid treatment
OIH during chronic opioid maintenance	Pain is abnormal in presentation (often with concurrent allodynia)	Abrupt	Pain worsens
	Pain may occur at a distant location from the original source or be widespread (panalgesia), and is poorly defined in terms of locality and quality
	OIH can be associated with delirium, agitation, seizures, and myoclonus
OIH after brief high doses of opioids	Large opioid doses may increase tenderness in skin and soft tissue; seen often in postoperative periods or hospitalizations for pain	Abrupt	Pain worsens; may be appropriate to switch to a piperidine derivative (eg, fentanyl)
	Inconsistent data and contradictory case reports
OIH after brief, low, or ultra-low doses of opioids	Little experimental work exists in humans, but rodent models suggest some evidence	Unknown	Pain may improve with increased dose

It is uncertain if the phenomenological differences in hyperalgesia induced by chronic maintenance or brief high or brief low doses of opioids have distinct mechanisms or if an OIH dosing continuum exists [43]

OIH opioid-induced hyperalgesia

(Adapted from Angst and Clark [43])