The development of opioid tolerance and dependence, through chronic and/or inappropriate use, increases the risk of problematic adverse effects and imposes severe social costs. Unfortunately, the high fatality rate of heroin overdose and incidences of addiction to prescription opiates continue to escalate.1–3 However, the associated risk of developing opiate dependence is difficult to predict due to large individual variability in opiate sensitivity.3 This imposes major implications to the likelihood of opioid addiction, addiction treatment, and analgesic drug dosing due to the possible risk of under or overdosing.
