Factors associated with using opiates while under extended-release naltrexone blockade: A descriptive pilot study

Extended-release naltrexone (XR-NTX) blocks the effects of opioids for 4weeks, yet many patients continue to use them. To learn more about why this occurs, we collected self-reports on subjective effects and drug use factors from participants' most recent heroin/opiate use while under XR-NTX blockade.

Participants (n=38) were unemployed, heroin-dependent adults enrolled in a randomized controlled trial evaluating employment-based incentives to promote adherence to XR-NTX. A subset of participants (n=18) were asked to complete a survey about their most recent use of heroin/opiates when they provided an opiate-positive urine sample while under XR-NTX blockade. Surveys were administered weekly, and participants could complete multiple surveys throughout the trial. Participants reported how high they were (11-point scale; 0=not at all, 10=extremely), how much heroin/opiates they took (less, more, or about the same as usual before starting naltrexone), whether they used cocaine at the same time, and the routes of administration for heroin/opiates and cocaine (if used). All analyses were descriptive.

Of the 107 surveys, 75.7% indicated being "not at all" high the last time heroin/opiates were used. 75.5% of surveys reported opiate amounts that were less than usual, and only 7.5% reported amounts larger than usual. Cocaine was used at the same time as heroin for 57.9% of surveys but typically through a different route (74.2%).

Using heroin/opiates while under XR-NTX blockade is not strongly associated with self-reports of high, taking larger than normal amounts of opiates, or taking opiates and cocaine simultaneously via the same route. Future research should incorporate measures of naltrexone concentration and more comprehensive and frequent assessments using ecological momentary assessment.