Craving is defined to be a measurable, subjective state associated with drug-related stimuli, which may co-occur with drug-taking behavior under certain pharmacological and/or ecological conditions. This study assessed whether naloxone-precipitated withdrawal would occasion opiate craving and, if so, whether reported craving would be greater when an opiate could be taken during withdrawal. Nine methadone-maintained volunteers participated in a repeated measures, randomized crossover design involving four test sessions. Under double-blind conditions, each volunteer was injected intramuscularly with saline on two test days and with 0.2 mg naloxone on two test days. On two days (one naloxone and one saline), volunteers were told that if the withdrawal distress was too intense they could choose to receive methadone 30 minutes after the test injection. However, this choice resulted in losing $10. Observer-rated physiological and subjective measures of opiate withdrawal, mood, and craving were assessed before naloxone or saline injection and for two hours afterwards. As predicted, naloxone precipitated significant opiate withdrawal. Opiate craving, as measured by a new multi-item scale, showed significant and parallel increases during precipitated withdrawal; in contrast, standard single-item questions failed to show any effect. Contrary to expectation, measures of opiate withdrawal, mood, and craving were not significantly influenced by drug availability, although mean scores tended to be highest in the naloxone/drug availability test session. The present findings have several important implications for conceptualizing and measuring opiate craving, and for investigating the functional relationship between drug craving and drug-taking behavior.
