Effects of fentanyl on cellular immune functions in man

In order to analyze the effects of the opioid agonist fentanyl on cells of the innate immune system, seven healthy individuals were treated intravenously with the opioid fentanyl and five subjects received a placebo. Respiratory burst of polymorphonuclear cells (PMNC) and phenotypes of peripheral blood lymphocytes (PBL) were analyzed from blood samples drawn before, 15 and 30 min after fentanyl or placebo application. In addition, in vitro effects of fentanyl on natural killer (NK) activity was assessed. Fentanyl administration affected neither superoxide production of PMNC nor circulating numbers of B-and T-lymphocytes. In contrast, NK cell (CD16+/CD56+) numbers significantly increased in response to fentanyl. However, no direct influence of fentanyl on NK cell function in vitro could be detected. These results suggest a transient effect of fentanyl on NK cell circulation which seemed to be centrally mediated rather than a direct effect of this opioid on NK cells.