High-sensitivity analysis of buprenorphine, norbuprenorphine, buprenorphine glucuronide, and norbuprenorphine glucuronide in plasma and urine by liquid chromatography–mass spectrometry

In the current study, buprenorphine (BUP) and its major metabolite, nor-buprenorphine (NBUP), were determined in hair samples from former heroin users following Suboxone® treatment. Hair samples from 36 subjects were analyzed. The drugs of interest were isolated from hair by solid-liquid extraction with methanol and were determined by liquid chromatography-mass spectrometry, using an electrospray ionization interface. The analytical parameters of the method (such as linearity, limits of quantification, recovery, accuracy, and precision) were determined. The inter-quartile range of BUP levels was from 11.4 to 37.4 pg/mg (mean value 56.6 pg/mg) for the proximal hair segment, from 5.8 to 43.3 pg/mg for the middle hair segment (mean value 25.3 pg/mg), while a range from 4.3 to 33.9 pg/mg (mean value 105.2 pg/mg) for the distant to the root hair segment was determined. For NBUP the corresponding inter-quartile range was from 27.0 to 147.6 for the proximal segment (mean value 95.4 pg/mg), from 21.5 to 164.7 pg/mg for the middle segment (mean value 102.0 pg/mg) and from 20.4 to 103.6 pg/mg for the distant segment (mean value 156.8 pg/mg). The mean BUP/NBUP concentration ratio was 0.5. The daily dose of Suboxone® correlated significantly with BUP and NBUP levels in hair (p = 0.001 and p = 0.023) as well as with the BUP/NBUP ratio (p = 0.010). No significant correlation was found between the levels of BUP and NBUP and the duration of Suboxone® administration. The developed and validated method was successfully used for the determination of BUP and NBUP in hair samples collected from former heroin users under Suboxone® treatment.

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A rapid and sensitive LC-MS/MS method was developed and validated for the simultaneous determination of buprenorphine and its three metabolites (buprenorphine glucuronide, norbuprenorphine and norbuprenorphine glucuronide) as well as naloxone and its metabolite naloxone glucuronide in the rat plasma. A hydrophilic interaction chromatography column and a mobile phase containing acetonitrile and ammonium formate buffer (pH 3.5) were used for the chromatographic separation. Mass spectrometric detection was achieved by an electrospray ionization source in the positive mode coupled to a triple quadrupole mass analyzer. The calibration curves for the six analytes displayed good linearity over the concentration range 1.0 or 5.0-1000 ng/mL. The intra and inter-day precision (CV) ranged from 2.68 to 16.4% and from 9.02 to 14.5%, respectively. The intra- and inter-day accuracy (bias) ranged from -14.2 to 15.2% and from -9.00 to 4.80%, respectively. The extraction recoveries for all the analytes ranged from 55 to 86.9%. The LC-MS/MS method was successfully applied to a pharmacokinetic study of buprenorphine-naloxone combination in rats.