[Effect on morphine and other opioids on immune function]

Already 1898 first clinical observations of a possible immune suppression after morphine intake were published. Today there are many reports describing opioid effects on nearly all parameters of the immune system. The question arises, whether there exists any evidence for clinical (harming) effects on patients.

Recent experimental and clinical publications are reviewed. Results are summarized, pathophysiological mechanisms and clinical conclusions discussed.

Morphine and other opioids have immunomodulating effects on nearly all measurable parts of the immune system (macrophages, granulocytes, nk-cells; mediators like Interleukin 1, 2 and 6, TNF). However, most studies did not include pain models, and in addition, high morphine doses were used. First studies using a combined pain/morphine-approach report immune stimulating effects. There are three pathophysiological mechanisms under discussion, including opioid receptors on immune competent cells, central opioid receptors activating the adrenergic system and opioid-induced steroid release with consecutive immunosuppression. It is completely unclear, if there is any relevance of these findings for clinical settings.

The question whether use of opioids can harm chronic pain patients is unsolved. There is an urgent need for studies in clinical settings with clinical relevant parameters.