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Heroin Addiction and Related Clinical Problems: 2008, 10, 4 (pages: 39 - 44)

Opioid Therapy and Restoration of the Immune Function in Heroin-Addicted Patients

Somaini L., Giaroni C., Gerra G.

Summary: There are several reports suggesting that opioid compounds may influence the immune response. Studies carried out in experimental animals and in humans have shown that both innate and acquired immunity are significantly affected by opioids. From a molecular viewpoint, opioids behave like cytokines, modulating the immune response by interacting with their receptors both in the central nervous system and in the periphery. One of the main features of opioid-mediated modulation of the immune function is the development of immunosuppression, which has been documented in injecting heroin abusers. Over the last few years, however, evidence has been provided to suggest that various opioid drugs may have distinctive effects on the immune function. Data obtained from animal studies have demonstrated, for instance, that long-acting opioids, such as methadone and buprenorphine, are devoid of any intrinsic immunosuppressive activity. In this connection, the hypothesis, which was first put forward some years ago, that the normalization of altered cellular immunity can, in injecting heroin abusers, be achieved through long-term methadone or buprenorphine treatment, has been positively re-evaluated in recent times. Our group has recently investigated the immune response in heroin-addicted patients currently under methadone or buprenorphine maintenance treatment, comparing them with untreated heroin addicts and healthy controls. In agreement with the data obtained by other groups, our study has provided evidence confirming the ‘immunoprotective' effect of long-acting opioid drugs. From a pathophysiological viewpoint, the ability of opioids to modulate the immune function may have some bearing on the development of the infectious diseases that are often associated with drug abuse. The high percentage of infections among injecting drug users is partly related to injection methods and life-style practices, but it is now accepted that heroin-induced immunosuppression may contribute as a co-factor in the contraction of several microbial and viral infections, such as Hepatitis C virus (HCV) infection. Conversely, in view of the ‘immunoprotective' action of some opioids, such as buprenorphine, it has now been proposed that the administration of these latter compounds may improve the outcome of chronic HCV virus infections.