Chronic exposure of human macrophages in vitro to morphine and methadone induces a putative tolerant/dependent state.

We have shown previously that whereas acute exposure of cultured murine peritoneal macrophages inhibits phagocytosis, chronic exposure results in a putative tolerant/dependent state. We now report similar observations using human cultured monocyte-derived macrophages (hMDM) from a control population and from methadone patients. With hMDM, acute exposure to morphine and methadone inhibited phagocytosis in a dose-dependent manner.