Buprenorphine Dosage and Urine Quantitative Buprenorphine, Norbuprenorphine, and Creatinine Levels in an Office-Based Opioid Treatment Program

BACKGROUND: Treatment progress is routinely monitored by urine testing in patients with opioid use disorder (OUD) undergoing buprenorphine medication-assisted treatment (MAT). However, interpretation of urine test results could be challenging. This retrospective study aims to examine the results of quantitative buprenorphine, norbuprenorphine, and creatinine levels in urine testing in relation to sublingual buprenorphine dosage to facilitate an accurate interpretation of urine testing results. METHODS: We reviewed the medical charts of 41 consecutive patients, who were residing in halfway houses where their medication intake was closely monitored and who had enrolled in an office-based MAT program at an urban clinic between July 2018 and June 2019. The patients’ urine testing results were reviewed, and demographic variables were recorded. We focused on the patients treated with 8-, 12-, or 16-mg/day of buprenorphine, examining their urine buprenorphine, norbuprenorphine, and creatinine levels. Analysis of variance tested the statistical association between the dosage and urine testing results on the norbuprenorphine-to-creatinine ratio. RESULTS: A total of 240 urine samples from 41 patients were included for this study. The 41 patients received a mean buprenorphine dose of 10.5 ± 3.7 mg/day (range, 4-20 mg/day). Then, this study examined the distribution of the 240 urine samples and then focused on 184 urine samples that came from the 33 patients who were treated with 8-, 12-, and 16-mg/day of buprenorphine, the 3 most common dosages. All of the 184 urine samples had a creatinine level of >20 mg/dL and buprenorphine-to-norbuprenorphine ratio <50:1. The average norbuprenorphine-to-creatinine ratio in the 8 mg/day dosage group was 3.85 ± 2.24 × 10(−4) (n = 66; range, 0.44-11.12). The respective ratios in the 12- and 16-mg dosage groups were 5.64 ± 3.40 × 10(−4) (n = 83; range, 1.55-22.72) and 6.23 ± 4.92 × 10(−4) (n = 35; range, 1.37-27.12). The 3 dosage groups differed significantly in the mean ratios (P < .01), except when the 12- and 16-mg dosage groups were compared (P = .58). The results of this study thus suggest that prescribers should pay attention to the following features: (1) unexpected substance(s) in urine testing, (2) creatinine level under 20 mg/dL, (3) buprenorphine-to-creatinine ratio over 50:1, (4) buprenorphine dosage over 24 mg/day, and (5) norbuprenorphine-to-creatinine ratio consistently under 0.5 × 10(−4) in patients treated with 8 mg/day or 1.5 × 10(−4) in patients treated with 12 mg/day or more. CONCLUSION: This study suggested parameters for interpreting quantitative urine test results in relation to buprenorphine intake dose in office-based opioid treatment programs.