Opiates and Their Immunomodulation Properties

Overview

Opiates have been recently used for suppression of the neuropathic pain or to relieve pain in patients with cancerdiseases. However, opiates are also used by drug abusers to achieve feeling of euphoria. These drugs influence notonly the nervous systembut they can alsomodulatemany other physiological functions including those of the immunesystem. Since opioid receptors have been found on the surface of cells of the immune system, two possiblemechanismsof opiate actions have to be considered. The first one represents a direct action of the opiates through the opioidreceptors on immune cells; the second mechanism is mediated by the nervous system. The immunomodulatoryproperties of the opiates have been demonstrated in numerous models. Especially the enhanced sensitivity to viraland bacterial infections, observed in drug abusers, is accounted to the side effects of opiates. Experimental animalmodels have shown even more complex actions of opiates, which can lead to suppression as well as to stimulationof individual immunological parameters. Although proliferation of lymphocytes tested in vitro after application ofopiates in vivo is generally reduced, production of the pro-inflammatory cytokines and some functions ofmacrophagescan be enhanced. Effects of opiate action depend on the experimental model used, the drug dose, way of drugapplication, time of testing and on the tested immunological parameter. This article summarizes recent knowledgeof effects of opiates on the functions of cells of the immune system. It also refers global problems of exploitationof illegal drugs and the importance of methadone in the substitution treatment.

Key words:
opiates, morphine, heroin, methadone, substitution treatment, immune system.