Exogenous and endogenous opioids as biological response modifiers.

Narcotic opioid compounds are among the most widely prescribed drug interventions for individuals suffering pain. Among the unwarranted side effects of respiratory depression, constipation, and physical dependence are the immunosuppressive qualities, particularly those which affect cell-mediated immunity. The immunosuppressive characteristics of opioid narcotics (e.g., morphine) have recently come into focus with the advent of acquired immune deficiency syndrome (AIDS) and the putative causative agent, human immunodeficiency virus type 1 (HIV-1). Specifically, a vast reservoir of HIV-1-infected individuals exists among drug abusers. Moreover, experimental evidence would suggest narcotic opioids may increase viral load in infected individuals by modifying the cellular machinery of activated leukocytes. Likewise, investigators have shown that opioids modify tumor growth and development. In this review, a comparison between endogenous opioid peptides and exogenous opiates on cell-mediated immunity and its relationship to viral infection and tumors is described.