Confirmatory analysis of buprenorphine, norbuprenorphine, and glucuronide metabolites in plasma by LCMSMS. Application to umbilical cord plasma from buprenorphine-maintained pregnant women

An LCMSMS method was developed and fully validated for the simultaneous quantification of buprenorphine (BUP), norbuprenorphine (NBUP), buprenorphine-glucuronide (BUP-Gluc), and norbuprenorphine-glucuronide (NBUP-Gluc) in 0.5 mL plasma, fulfilling confirmation criteria with two transitions for each compound with acceptable relative ion intensities. Transitions monitored were 468.3 > 396.2 and 468.3 > 414.3 for BUP, 414.3 > 340.1 and 414.3 > 326.0 for NBUP, 644.3 > 468.1 and 644.3 > 396.3 for BUP-Gluc, and 590.3 > 414.3 and 590.3 > 396.2 for NBUP-Gluc. Linearity was 0.1–50 ng/mL for BUP and BUP-Gluc, and 0.5–50 ng/mL for NBUP and NBUP-Gluc. Intra-day, inter-day, and total assay imprecision (%RSD) were <16.8%, and analytical recoveries were 88.6–108.7%. Extraction efficiencies ranged from 71.1 to 87.1%, and process efficiencies 48.7 to 127.7%. All compounds showed ion enhancement, except BUP-Gluc that demonstrated ion suppression: variation between 10 different blank plasma specimens was <9.1%. In six umbilical cord plasma specimens from opioid-dependent pregnant women receiving 14–24 mg/day BUP, NBUP-Gluc was the predominant metabolite (29.8 ± 7.6 ng/mL), with BUP-Gluc (4.6 ± 4.8 ng/mL), NBUP (1.5 ± 0.8 ng/mL) and BUP (0.4 ± 0.2 ng/mL). Although BUP biomarkers can be quantified in umbilical cord plasma in low ng/mL concentrations, the significance of these data as predictors of neonatal outcomes is currently unknown.