Neutrophil function and opioid receptor expression on leucocytes during chronic naltrexone treatment in humans

We report that neutrophil function was impaired in former heroin addicts on chronic naltrexone maintenance. Of the subjects, 62.5% had elevated plasma ACTH, 25% had elevated plasma cortisol and one subject had increased urina ry cortisol. All subjects showed enhanced expression of opioid receptors on monocytes, neutrophils and lymphocytes. In vitro, incubation with therapeu tically relevant concentrations of naltrexone induced a slow increase of ne utrophil cytoplasmatic free Ca2+ concentrations ([Ca2+](i)) and slowed down the [Ca2+](i) rise induced by N-formyl-methionyl-leucyl-phenylalanine. Nei ther naltrexone nor its metabolite beta-naltrexol affected human neutrophil function in vitro. We conclude that impairment of neutrophil function duri ng chronic naltrexone may be related to opioid receptor overexpression. Wit h this regard, the possible role of naltrexone-induced [Ca2+](i) changes de serves further investigation. (C) 1999 Academic Press.