Opioid vs. money choice preference patterns in regular heroin users

About two-thirds of people treated for opioid use disorder (OUD) return to opioid use within the first-year post-treatment, and about 10% report use while on agonist therapy. Understanding determinants of opioid-seeking is vital to reducing recurrence and its risks. We assessed individual differences in effortful choices between opioid and money amounts, modeling real-world choices. Our lab conducted studies in which regular heroin-users were stabilized on buprenorphine to suppress withdrawal. Within experimental sessions, the participant could choose repeatedly across 12 trials between units of hydromorphone (HYD, 1 or 2 mg IM) vs. money ($2 or $4); HYD and money amounts differed parametrically across studies. After initiating a choice for HYD or money (one mouse-click) on each trial, the work required to earn the same commodity increased exponentially across later trials. We analyzed trial-by-trial choices (drug vs. money) and latencies (speed to choose) and correlated these patterns with individual differences. Participants with recent pre-experiment cocaine use and those who chose HYD on the first trial during sessions took significantly longer to choose money than HYD (i.e. difference in median latencies). Faster latency to choose drug (vs. money) correlated with significantly greater effortful responding for drug (vs. money). The strongest predictor of high effortful responding for drug was whether the initial choice a participant made in a session was for HYD or money. These results highlight that recent cocaine use and participants with faster relative decisional speed for drug (than money) may be more likely to engage in effortful opioid-seeking behavior.