An Approach for Improving the Detection and Quantitation of Buprenorphine and Its Metabolites in Maternal and Neonatal Hair.

Background: Buprenorphine (BUP) use is prevalent in pregnant women with opioid use disorder (OUD). Drug monitoring during pregnancy is critical for optimizing dosing regimen and achieving the desired clinical outcomes. Hair can be used as a critical biological matrix for monitoring long-term exposure to drugs. The aim of this study was to optimize the methodology used to quantify BUP and its metabolites in hair samples.

Methods: Conditions for hair sample processing (ie, hair washing, incubation temperature, and extraction time) were optimized to maximize extraction recovery. The LC-MS/MS strategy employed here used 4 deuterated internal standards for quantifying BUP and its major metabolites [norbuprenorphine (NBUP), buprenorphine glucuronide (BUP-G), and norbuprenorphine-glucuronide (NBUP-G)] in human hair samples. The optimized conditions were used to measure BUP and its metabolites in hair samples of 5 women undergoing OUD treatment and their neonates.

Results: Unwashed hair samples processed by shaking with acetonitrile for 24 hours at 37 °C showed higher BUP (36%) and NBUP (67%) recovery, compared with those processed by incubation at room temperature. The standard curves showed excellent linearity over 0.05-100 ng/mL for BUP and NBUP and 0.1-200 ng/mL for BUP-G and NBUP-G. The assay was partially validated for reproducibility and accuracy and was successfully used for measuring BUP and metabolites in aforementioned hair samples. BUP was identified in all hair samples, while BUP-G was not. BUP was the primary analyte in maternal hair (median: 38.3 pg/mg; 25-75 percentile: 17-152.4 pg/mg), while NBUP-G was predominant in neonatal hair (median: 28.6 pg/mg; 25%-75% percentile: 1.9-112.8 pg/mg).

Conclusions: The methodology used for quantifying BUP and its metabolites in hair samples of maternal female patients and their neonates is simple, accurate, and reproducible. The developed method may be useful for measuring fetal exposure to BUP during gestation.