Immunologic effects of opioids in the presence or absence of pain.

Opioids are acknowledged to suppress immune functions following both acute and chronic administration; however, there appear to be differences according to the schedule of administration as well as the state of the organism. For example, whereas a single dose of morphine in the absence of pain is well known to be immune suppressive, the biologic consequences of this suppression are largely unknown. Repeated and chronic opioid ingestion in the absence of pain appears to result in significant consequences including high infectious disease prevalence. On the other hand, in the presence of acute pain, there is evidence that opioid administration in analgesic doses is protective. Much less is known regarding the immune and disease implications related to chronic opioid treatment for chronic pain states.