Determination of buprenorphine, norbuprenorphine, naloxone, and their glucuronides in urine by liquid chromatography-tandem mass spectrometry.

A liquid chromatography-tandem mass spectrometry method for the simultaneous quantification of buprenorphine (BUP), norbuprenorphine (NBUP), naloxone (NAL), and their glucuronide conjugates BUP-G, NBUP-G, and NAL-G in urine samples was developed. The method, omitting a hydrolysis step, involved non-polar solid-phase extraction, liquid chromatography on a C18 column, electrospray positive ionization, and mass analysis by multiple reaction monitoring. Quantification was based on the corresponding deuterium-labelled internal standards for each of the six analytes. The limit of quantification was 0.5 µg/L for BUP and NAL, 1 µg/L for NAL-G, and 3 µg/L for NBUP, BUP-G, and NBUP-G. Using the developed method, 72 urine samples from buprenorphine-dependent patients were analysed to cover the concentration ranges encountered in a clinical setting. The median (maximum) concentration was 4.2 µg/L (102 µg/L) for BUP, 74.7 µg/L (580 µg/L) for NBUP, 0.9 µg/L (85.5 µg/L) for NAL, 159.5 µg/L (1370 µg/L) for BUP-G, 307.5 µg/L (1970 µg/L) for NBUP-G, and 79.6 µg/L (2310 µg/L) for NAL-G.