Exploring Opioid Use Disorder Outcomes by Quantitative Urinalysis: Post Hoc Analysis of a Phase 3 Randomized Clinical Trial

Objectives: Opioid use disorder (OUD) is a global concern. Urine drug screening uses opioid immunoassays to monitor OUD treatment response but is limited to yes/no results. Analytical cutoff variation complicates interstudy comparisons. This study investigated whether quantitative urinalysis can provide additional clinically meaningful treatment efficacy information and assessed the impact of different cutoffs on treatment differences. Methods: Quantitative urine drug test data were analyzed from a randomized, active-controlled, parallel-group, double-blind, 31-week phase 3 trial (N = 428; December 29, 2015, to October 19, 2016) assessing CAM2038 subcutaneous (SC) buprenorphine (BPN) extended-release injections compared to daily sublingual (SL) BPN/naloxone (BPN/NX) tablets, and equivalent placebos, in OUD treatment (NCT02651584). Urine samples were analyzed by gas or liquid chromatography with mass spectrometry. The European Medicines Agency (EMA)–directed primary endpoint, based on opioid detection above the lower limit of quantification (LLOQ), was explored using different cutoffs. Results: Using the LLOQ, the mean percentage of opioid-negative samples was 35.1% and 28.4% for CAM2038 and SL BPN/NX, respectively (mean difference [95% confidence interval], 6.7% [-0.1% to 13.6%]). Using standard cutoffs (1 ng/mg creatinine [fentanyl/norfentanyl], 300 ng/mg creatinine [other opioids]), results were 41.2% and 32.2% (9.0% [1.8%–16.1%]). Increasing cutoffs led to greater differences favoring CAM2038. Significant differences in mean concentrations over time and cumulative distribution of exposure to different opioids also favored CAM2038. The difference in fentanyl exposure between treatments was nonsignificant. Conclusions: Quantitative urinalysis provides insights into opioid use beyond assessment of abstinence. Study outcomes are impacted by analytical thresholds, which should be carefully considered when designing, interpreting, and comparing clinical trial results.