Abuse liability of oxycodone as a function of pain and drug use history

Abstract

The relationship between pain and prescription opioid abuse is poorly understood. Determining whether a patient is seeking additional opioid medications in order to alleviate pain or to abuse the drugs can be difficult. The present study was designed to evaluate two variables that may influence the abuse liability of opioids: drug use history and the presence or absence of experimentally induced pain. Eighteen healthy participants completed this outpatient study. One group was abusing prescription opioids (N=9) and one group had used prescription opioids medically but did not abuse them (N=9). All participants completed twelve sessions during which the effects of orally delivered oxycodone (0, 15, 30mg/70kg, PO) were examined. One dose was tested per day under double-blind conditions and sessions were separated by at least 48h. During the first "sample" session each week, participants were given $10 and the dose that was available later that week. During the second "choice" session, participants could self-administer either money or the previously sampled dose. Six sessions involved repeated hand immersions in cold water (4 degrees C) and six sessions involved immersions in warm water (37 degrees C). Most of the positive subjective effects of oxycodone were similar between the groups, but oxycodone self-administration significantly differed between groups. Non-abusers self-administered active doses of oxycodone only when they were in pain while abusers self-administered oxycodone regardless of the pain condition. These data suggest that an assessment of the reinforcing effects of opioids may be a sensitive method for differentiating opioid abusers from non-abusers.

Figure 1

Average (± 1 standard error of the mean, SEM) progressive ratio breakpoint values for drug (left panels) and money (middle panels), and amount of drug self-administered (right panels) as a function of available dose and water temperature (4°C, 37°C) in non-drug abusers (top panels) and drug abusers (bottom panels). * represents a significant difference from placebo, # represents a significant difference between the cold and warm water conditions. One symbol represents p<0.05, two symbols represent p<0.01, three symbols represent p<0.001, and four symbols represent p<0.0001.

Figure 2

Average (± 1 SEM) ratings for selected items on the visual analog scale as a function of dose and time in non-drug abusers (top panels) and drug abusers (bottom panels). For clarity, significance symbols are not shown.

Figure 3

Average (± 1 SEM) sum scores on the short form of the McGill Pain Questionnaire (range: 15–60; left panels), and responses to the questions “How painful is it?” (middle panels), and “How much does it bother you?” (right panels) after the cold water immersion as a function of dose and time in non-drug abusers (top panels) and drug abusers (bottom panels). For clarity, significance symbols are not shown.