Quantitative Analysis of Buprenorphine and Norbuprenorphine in Urine using Liquid Chromatography Tandem Mass Spectrometry

Screening for drugs of abuse: which matrix, oral fluid or urine?

Urine is recognized as the prime matrix for drug test screening with well-established methods and testing protocols. Its major limitation is with regard to the inconvenience of sample collection and lack of integrity due to adulteration, dilution, drug spiking or sample exchange. The question is whether oral fluid, with its apparent better sample integrity, can replace urine for drug screening. This review examines the sample integrity problems and the advantages and limitations of oral fluid and urine in drug screening programmes. The variety of sample collection devices for oral fluid is shown to be a problem with recovery and detection for some drugs. This is examined in relation to the pharmacokinetics of drug metabolism and excretion in this matrix. Buccal contamination with drugs in oral fluid may also cause problems with interpretation. The clinical advantages of oral fluid analysis compared with urine testing are highlighted. Parent drugs are often found in oral fluid where only their metabolites may be found in urine, for example the benzodiazepines. 6-Monoacetylmorphine, an indicative marker of heroin, has a high prevalence in oral fluid from users of this drug but its detection in urine is limited due to its short half-life. Advances in analytical techniques, particularly chromatography linked to tandem mass spectrometry, are helping to promote oral fluid analysis. However, the lack of concordance studies examining both urine and oral fluid drug levels and kinetics in the clinical setting is of some concern.

Combined liquid chromatography-coulometric detection and microextraction by packed sorbent for the plasma analysis of long acting opioids in heroin addicted patients

The sublingual combination of buprenorphine and naloxone (Suboxone(®)) and Methadone Maintenance Therapy have been found effective in treating heroin addiction. A new analytical method suitable for the simultaneous determination of buprenorphine, norbuprenorphine, methadone and naloxone in human plasma by means of liquid chromatography with coulometric detection has been developed. The chromatographic separation was achieved with a phosphate buffer-acetonitrile mixture as the mobile phase on a cyano column. The monitoring cell of the coulometric detector was set at an oxidation potential of +0.600 V. A rapid clean-up procedure of the biological samples using a microextraction by packed sorbent technique has been implemented, employing a C8 sorbent inserted into a syringe needle. The extraction yield values were satisfactory for all analytes (>85%). The calibration curves were linear over a range of 0.25-20.0 ng mL(-1) for buprenorphine and norbuprenorphine, 3.0-1000.0 ng mL(-1) for methadone and 0.13-10.0 ng mL(-1) for naloxone. The sensitivity was also high with limits of detection of 0.08 ng mL(-1) for both buprenorphine and norbuprenorphine, 0.9 ng mL(-1) for methadone and 0.04 ng mL(-1) for naloxone. The intraday and interday precision data were always satisfactory. The method was successfully applied to plasma samples obtained from former heroin addicts treated with opioid replacement therapy.

Issues pertaining to the analysis of buprenorphine and its metabolites by gas chromatography-mass spectrometry

"Substitution therapy" and the use of buprenorphine (B) as an agent for treating heroin addiction continue to gain acceptance and have recently been implemented in Taiwan. Mature and widely utilized gas chromatography-mass spectrometry (GC-MS) technology can complement the low cost and highly sensitive immunoassay (IA) approach to facilitate the implementation of analytical tasks supporting compliance monitoring and pharmacokinetic/pharmacogenetic studies. Issues critical to GC-MS analysis of B and norbuprenorphine (NB) (free and as glucuronides), including extraction, hydrolysis, derivatization, and quantitation approaches were studied, followed by comparing the resulting data against those derived from IA and two types of liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods. Commercial solid-phase extraction devices, highly effective for recovering all metabolites, may not be suitable for the analysis of free B and NB; acetyl-derivatization products exhibit the most favorable chromatographic, ion intensity, and cross-contribution characteristics for GC-MS analysis. Evaluation of IA, GC-MS, and LC-MS/MS data obtained in three laboratories has proven the 2-aliquot GC-MS protocol effective for the determination of free B and NB and their glucuronides.

Development and validation of a liquid chromatography-tandem mass spectrometry assay for the simultaneous quantification of buprenorphine, norbuprenorphine, and metabolites in human urine

A liquid chromatography-tandem mass spectrometry method for the simultaneous quantification of buprenorphine (BUP), norbuprenorphine (NBUP), buprenorphine glucuronide (BUP-Gluc), and norbuprenorphine glucuronide (NBUP-Gluc) in human urine was developed and fully validated. Extensive endogenous and exogenous interferences were evaluated and limits of quantification were identified empirically. Analytical ranges were 5-1,000 ng/mL for BUP and BUP-Gluc and 25-1,000 ng/mL for NBUP and NBUP-Gluc. Intra-assay and interassay imprecision were less than 17% and recovery was 93-116%. Analytes were stable at room temperature, at 4 degrees C, and for three freeze-thaw cycles. This accurate and precise assay has sufficient sensitivity and specificity for urine analysis of specimens collected from individuals treated with BUP for opioid dependence.

Simultaneous determination of methadone, buprenorphine and norbuprenorphine in biological fluids for therapeutic drug monitoring purposes

Methadone and buprenorphine are two of the drugs most frequently used for abstinence from illicit opioids and in the treatment of pain. A sensitive and selective high-performance liquid chromatographic method with diode array detection for the simultaneous determination of methadone, buprenorphine and norbuprenorphine has been developed. Separation of the three analytes was obtained by using a reversed-phase column (C8, 250mmx4.6mm i.d., 5microm) and a mobile phase composed of 40% phosphate buffer containing triethylamine, 50% methanol and 10% acetonitrile (final apparent pH 6.0). Loxapine was used as the internal standard. An accurate pre-treatment procedure of biological samples was developed, using solid-phase extraction with C8 cartridges (100mg, 1mL) and needing small amounts of plasma or urine (300microL). The calibration curves were linear over a working range of 10.0-1500.0ng/mL for methadone and of 5.0-500.0ng/mL for buprenorphine and norbuprenorphine in both matrices. The limit of quantitation (LOQ) and the limit of detection (LOD) were 1.0 and 0.4ng/mL for methadone and 0.5 and 0.2ng/mL for both buprenorphine and norbuprenorphine, respectively. The method was successfully applied to the analysis of plasma and urine samples from patients undergoing treatment with these drugs. Precision and accuracy results were satisfactory and no interference from endogenous or exogenous compounds was found. The method is suitable for the simultaneous determination of methadone and buprenorphine in human plasma and urine for therapeutic drug monitoring purposes.