Opioid addiction is a complex syndrome involving a maladaptive pattern of drug use that is characterized by tolerance, physical dependence (withdrawal during abstinence), continued drug use despite acknowledged harm from the drug, excessive preoccupation with use of the drug, and social isolation. A medication that reduces the physiological manifestations could be an important part of addiction prevention and treatment, but would not address all of the complex neuroplastic events that underlie the overall symptom complex [66,67]. In contrast, the increased use of opioid narcotics for control of chronic pain has focused attention on the physical dependence associated with chronic opioid use. Although a patient receiving chronic opioid medications may not develop addiction, the physical dependence, tolerance and hyperalgesia that can develop may limit the value of chronic narcotic therapy and can complicate ongoing patient management [34,68]. Therefore, treatment with 5-HT3 antagonists may provide part of the solution to significant public health problems associated with opioid use.
