Immunotoxicology of opioids, inhalants, and other drugs of abuse.

Drug abuse is a problem of increasing worldwide significance. In addition to the obvious socioeconomic problems associated with the use of so-called street drugs, the abuse of ethical pharmaceuticals may also result in serious untoward health effects depending upon a wide range of variables (Chiang and Goldfrank 1990). One possible medical complication of drug abuse is modulation of the immune system, or immunotoxicity (Pillai and Watson 1990). The immune system is a highly regulated organ system that presents a variety of potential targets for modulation by drugs. This modulation may take the form of immunosuppression, leading to an enhanced susceptibility to infection or neoplasia; conversely, it may take the form of immunostimulation, resulting in hypersensitivity (allergy) or autoimmunity (Luster and Rosenthal 1993). Closely associated with drug abuse in recent years has been the emergence of the acquired immunodeficiency syndrome (AIDS), a retroviral infection spread by sexual contact or hematogenously by the sharing of needles among intravenous (IV) drug abusers. One of the hallmarks of AIDS is a profound and irreversible suppression of immune competence, usually resulting in death of the host from opportunistic infections. Thus, the combination of drug abuse and human immunodeficiency virus (HIV) infection represents a formidable challenge to the immune system. Although the scientific literature is replete with studies describing drug-related immunosuppression, the sheer number of abused drugs precludes detailed examination using traditional methodology. Moreover, as new therapeutics are developed for the treatment of drug abuse, an efficient screening approach will be required to assess their immunomodulatory potential.