At the end of the study, and once analysis of the main outcome variables were conducted, the medication assignment blind was broken and all day-6 urines of those assigned to take naltrexone as well as a random selection (n=10) assigned to take placebo were analyzed for naltrexone/6beta-naltrexol levels by LC-MS/MS (Laboratory of Peter Jatlow M.D., Yale University School of Medicine) to assure proper medication assignment and compliance. All subjects assigned to the naltrexone group had evidence of urine naltrexone/6beta-naltrexol while the placebo group had no measureable levels.
