The aim of this study was to develop and validate a method for the determination of buprenorphine (BUP), norbuprenorphine (NBUP) and naloxone (NAL) in fingernails and urine samples collected from former heroin users under suboxone substitution therapy. The analytes were extracted by solid-liquid or solid-phase extraction and were analyzed by liquid chromatography-mass spectrometry. The validation of the analytical methods developed included linearity, recovery, accuracy, precision, ion suppression, sensitivity of interfaces and limits of determination and quantification. The validated methods were applied to samples from 46 individuals. The majority of the urine samples were positive for all analytes (93.5% for BUP, 95.7% for NBUP and 84.8% for NAL). In nails, a higher detection rate was observed for NBUP and BUP (89.1%), compared with NAL (10.9%). The median values of the NBUP/BUP and the NAL/BUP ratio were 2.5 and 0.3 in urine and 0.8 and 0.3 in nails, respectively. A statistically significant correlation was found between the BUP, NBUP and total BUP (BUP and NBUP) concentrations in urine and those in nails. A weak correlation was observed between the daily dose (mg/day) and total BUP (P = 0.069), or NBUP (P = 0.072) concentrations in urine. In contrast, a strong correlation was found between the total amount of BUP administered during the last 12 months and total BUP (P = 0.038), or NBUP (P = 0.023) concentrations in urine. Moreover urine BUP, NBUP and total BUP concentrations correlated significantly. Our study demonstrated successfully the application of the developed method for the determination of the three analytes in urine and nails.

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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