Quantitative determination of R/S-methadone in human serum using ultra-high performance supercritical fluid chromatography-tandem mass spectrometry: A method for routine use

Methadone has two enantiomers, which exhibit differences in pharmacological effects, with R-methadone being the active and S-methadone the inactive enantiomer. A robust, simple and rapid method for chiral separation of the two enantiomers in serum samples using ultra-high performance supercritical fluid chromatography-tandem mass spectrometry (UHPSFC-MSMS) has been developed and validated. Enantiomeric separation was achieved using a Chiralpak IH-3 column with a mobile phase consisting of CO2 and 30mM ammonium acetate in methanol/water (98/2, v/v). Runtime was 4 minutes. Sample preparation was semi-automated using a Hamilton ML Star robot with protein precipitation, and phospholipid removal was carried out using a Waters OSTRO™ 96-well plate. The calibration range was 50.0-1,500 nM for each enantiomer. The between-assay relative standard deviations were in the range of 1.2-3.6%. Matrix effects ranged from 99% to 115% corrected with internal standard. The method has been implemented in our laboratory and has proven to be a robust and reliable method for determining the ratio of R/S-methadone in authentic patient samples.

Conductive vial electromembrane extraction of opioids from oral fluid

The use of oral fluid as sample matrix has gained significance in the analysis of drugs of abuse due to its non-invasive nature. In this study, the 13 opioids morphine, oxycodone, codeine, O-desmethyl tramadol, ethylmorphine, tramadol, pethidine, ketobemidone, buprenorphine, fentanyl, cyclopropylfentanyl, etonitazepyne, and methadone were extracted from oral fluid using electromembrane extraction based on conductive vials prior to analysis with ultra-high performance liquid chromatography-tandem mass spectrometry. Oral fluid was collected using Quantisal collection kits. By applying voltage, target analytes were extracted from oral fluid samples diluted with 0.1% formic acid, across a liquid membrane and into a 300 μL 0.1% (v/v) formic acid solution. The liquid membrane comprised 8 μL membrane solvent immobilized in the pores of a flat porous polypropylene membrane. The membrane solvent was a mixture of 6-methylcoumarin, thymol, and 2-nitrophenyloctyl ether. The composition of the membrane solvent was found to be the most important parameter to achieve simultaneous extraction of all target opioids, which had predicted log P values in the range from 0.7 to 5.0. The method was validated in accordance to the guidelines by the European Medical Agency with satisfactory results. Intra- and inter-day precision and bias were within guideline limits of ± 15% for 12 of 13 compounds. Extraction recoveries ranged from 39 to 104% (CV ≤ 23%). Internal standard normalized matrix effects were in the range from 88 to 103% (CV ≤ 5%). Quantitative results of authentic oral fluid samples were in accordance with a routine screening method, and external quality control samples for both hydrophilic and lipophilic compounds were within acceptable limits.

Determination of amphetamine enantiomers in urine by conductive vial electromembrane extraction and ultra-high performance supercritical fluid chromatography tandem mass spectrometry

Separation and quantification of amphetamine enantiomers is commonly used to distinguish between consumption of prescription amphetamine (mostly S-amphetamine) and illicit forms of the drug (racemate). In this study, electromembrane extraction with prototype conductive vials was combined with ultra-high performance supercritical fluid chromatography (UHPSFC-MS/MS) to quantify R- and S-amphetamine in urine. Amphetamine was extracted from 100 μL urine, diluted with 25 μL internal standard solution and 175 μL 130 mM formic acid, across a supported liquid membrane (SLM) consisting of 9 μL of a 1:1(v/v) mixture of 2-nitrophenyloctyl ether (NPOE) and bis(2-ethylhexyl)phosphite (DEHPi) into an acceptor phase containing 300 μL 130 mM formic acid. The extraction was facilitated by the application of 30 V for 15 min. Enantiomeric separation was achieved using UHPSFC-MS/MS with a chiral stationary phase. The calibration range was 50-10 000 ng/mL for each enantiomer. The between-assay CV was ≤5%, within-assay CV ≤1.5% and bias within ±2%. Recoveries were 83-90% (CV ≤6%), and internal standard corrected matrix effects were 99-105 (CV≤2%). The matrix effects ranged from 96 to 98% (CV≤8%) when not corrected by the internal standard. The EME method was compared to a chiral routine method that employed liquid-liquid extraction (LLE) for sample preparation. Assay results were in agreement with the routine method, and the mean deviation between methods was 3%, ranging from -21% to 31%. Finally, sample preparation greenness was assessed using the AGREEprep tool, which resulted in a greenness score of 0.54 for conductive vial EME, opposed to 0.47 for semi-automated 96-well LLE.

Serum or Plasma for Quantification of Direct Oral Anticoagulants?

BACKGROUND

Direct oral anticoagulants are increasingly replacing vitamin K antagonists for prevention of stroke in patients with atrial fibrillation, partly owing to the lack of a need for routine monitoring. Therapeutic drug monitoring may still be warranted under certain circumstances. It is generally assumed that serum and plasma can be interchangeably used for this purpose. The aim of this study was to investigate possible differences between the serum, citrate-plasma, and ethylenediaminetetraacetic acid (EDTA)-plasma concentrations of apixaban and rivaroxaban in a larger patient group and their relation to factor X measurements.

METHODS

Plasma and serum samples were drawn during the same venipuncture from patients treated with apixaban or rivaroxaban. Drug levels were measured using ultrahigh-performance liquid chromatography combined with tandem mass spectrometry. Three sample matrices were obtained from 8 healthy volunteers for measurement of factor X antigen and activity.

RESULTS

Mean concentrations of apixaban and rivaroxaban were 16.8% and 36.6% higher in serum than in citrate-plasma, respectively (both P < 0.001). The corresponding differences in serum versus EDTA-plasma were 4.5% for apixaban and 13.1% for rivaroxaban (both P < 0.001). Factor X antigen measurements in citrate-plasma, EDTA-plasma, serum with clot activator, and serum without additives yielded comparable results, and factor X activity was significantly higher in serum than in plasma.

CONCLUSIONS

Apixaban and rivaroxaban concentrations were significantly higher in serum than in plasma. The difference was more pronounced with rivaroxaban and was larger between serum and citrate-plasma than between serum and EDTA-plasma. Higher factor X activity in serum may explain the observed concentration differences. The choice of matrix is, thus, important when interpreting therapeutic drug monitoring results and in research involving analyses of direct oral anticoagulants. The authors recommend citrate-plasma as the preferred matrix.

Stability of Direct Oral Anticoagulants and Antiarrhythmic Drugs in Serum Collected in Standard (Nongel) Serum Tubes Versus Tubes Containing Gel Separators

BACKGROUND

Separation gels are often used in collection tubes, but adsorption of drugs onto the gel may cause falsely low concentrations in therapeutic drug monitoring. In this study, the stability of apixaban, edoxaban, rivaroxaban, flecainide, amiodarone, and desethylamiodarone was assessed in tubes, with and without gel separators.

METHODS

Drug-free blood was spiked and stored for up to 7 days in nongel tubes and gel tubes from 2 manufacturers (Vacuette and Vacutainer). The samples were analyzed in triplicates using ultra-high-pressure liquid chromatography-tandem mass spectrometry.

RESULTS

At ambient temperature conditions, the serum concentrations of apixaban, edoxaban, and rivaroxaban in a tube with acrylic-based gel had already decreased at baseline, whereas it took 6 hours to observe the same result in a tube with olefin-based gel. At 4°C, the reduction in serum concentration was considerably slower. For flecainide, the gel tube concentrations were stable at ambient temperature for 3 days, but decreased after 7 days in acrylic-based gel tubes. Amiodarone and desethylamiodarone stored in gel tubes at 4°C showed decrease in concentrations after 24 hours and 6 hours, respectively.

CONCLUSIONS

Acrylic-based gel tubes should not be used for any of the tested drugs. Although olefin-based gel tubes may be used for anticoagulants and flecainide, it is advisable to prefer nongel tubes as a general precaution.

Determination of psychoactive drugs in serum using conductive vial electromembrane extraction combined with UHPLC-MS/MS

Conductive vial electromembrane extraction (EME) with prototype equipment was applied for the first time to extract lipophilic basic drugs from serum. With this equipment, traditional platinum electrodes were replaced with sample and acceptor vials made from a conductive polymer, making the electrodes fully integrated and disposable. EME was combined with UHPLC-MS/MS, and a method to determine selected psychoactive drugs (alimemazine, amitriptyline, atomoxetine, clomipramine, doxepin, duloxetine, fluvoxamine, levomepromazine, nortriptyline and trimipramine) and metabolites (desmethyl clomipramine and desmethyl doxepin) in serum was developed, optimized, and validated. Extractions were carried out with 50 V for 15 min from serum samples (100 µL) diluted 1:3 with formic acid (0.1% v/v), using 2-nitrophenyl octyl ether as the supported liquid membrane (SLM), and formic acid (0.1% v/v, 300 µL) as acceptor phase. Using conductive vial EME, the extraction of lipophilic drugs reached exhaustive or near-exhaustive conditions, with recoveries in the range 75-117%. The method demonstrated excellent accuracy and precision, with bias within ± 6%, and intra- and inter-day CVs ranging 0.9 - 6% and 2 - 6%, respectively. In addition, acceptor phases were completely free of glycerophosphocholines. EME-UHPLC-MS/MS was successfully applied in determination of psychoactive drugs in 30 patient samples, and the results were in agreement with the current hospital routine method at St. Olav University Hospital (Trondheim, Norway). Obtaining comparable results to well-established routine methods is highly important for future implementation of EME into routine laboratories. These results thus serve as motivation for further advancing the EME technology. Until now, EME has been carried out with laboratory-build equipment, and the introduction of commercially available standardized equipment is expected to have a positive impact on future research activity.

Association between low body weight and cytochrome P-450 enzyme activity in patients with anorexia nervosa

Very little is known to which extent severe underweight could affect cytochrome P‐450 (CYP) enzyme activity. In this study, 24 patients with anorexia nervosa at two occasions ingested single oral doses of five test drugs known to be metabolized by CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4, respectively. A mixed model analysis was used to evaluate the effect of changes in body mass index (BMI) on the metabolic activities of these enzymes. The primary end point was the change in drug/metabolite ratio of each of the test drugs per kg/m² change in BMI. With increasing BMI, the metabolic activity of CYP3A4 decreased (change in the CYP3A4 drug/metabolite ratio per unit change in BMI = 0.056; 95% confidence interval [CI] 0.011 to 0.102; P = .017). For CYP1A2, increasing BMI increased the metabolic activity with borderline significance (change in the CYP1A2 drug/metabolite ratio per unit change in BMI = –0.107; CI –0.220 to 0.005; P = .059). For CYP2C9, CYP2C19, and CYP2D6, no significant changes were seen. The clinical impact of these findings for drug treatment in patients with anorexia nervosa and other severely underweight patients needs to be further studied by examining the pharmacokinetics of specific drugs. This might be particularly relevant for drugs metabolized by CYP1A2 and/or CYP3A4.

EtG and EtS in Autopsy Blood Samples With and Without Putrefaction Using UPLC-MS-MS

Analytical challenges related to postmortem specimens are well known. The degree of putrefaction of the corpse will influence the quality of the blood samples, and both the efficiency of sample preparation and the subsequent chromatographic performance can be affected. An ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS-MS) method was developed and validated for the determination of ethyl glucuronide (EtG) and ethyl sulfate (EtS) in postmortem whole blood. Sample preparation prior to UPLC-MS-MS analysis consisted of protein precipitation and filtration through a phospholipid removal plate. Chromatography was achieved using an HSS T3 column and gradient elution with formic acid in water in combination with methanol. The injection volume was 0.5 µL. Negative electrospray ionization was performed in the multiple reaction monitoring mode. Two transitions were monitored for the analytes and one for the internal standards. The between-assay relative standard deviations were in the range of 1.7-7.0% and the limits of quantification were 0.025 and 0.009 mg/L for EtG and EtS, respectively. Recovery was 51-55% and matrix effects ranged from 98% to 106% (corrected with internal standard). Blood samples from nine autopsy cases with various extents of putrefaction were analyzed. The sample preparation efficiently removed the phospholipids from the blood specimens. The samples were clean and the analytical quality of the chromatographic performance was satisfactory for both analytes irrespective of the degree of putrefaction.

A validated method for simultaneous determination of codeine, codeine-6-glucuronide, norcodeine, morphine, morphine-3-glucuronide and morphine-6-glucuronide in post-mortem blood, vitreous fluid, muscle, fat and brain tissue by LC-MS

The toxicodynamics and, to a lesser degree, toxicokinetics of the widely used opiate codeine remain a matter of controversy. To address this issue, analytical methods capable of providing reliable quantification of codeine metabolites alongside codeine concentrations are required. This article presents a validated method for simultaneous determination of codeine, codeine metabolites codeine-6-glucuronide (C6G), norcodeine and morphine, and morphine metabolites morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) in post-mortem whole blood, vitreous fluid, muscle, fat and brain tissue by high-performance liquid chromatography mass spectrometry. Samples were prepared by solid-phase extraction. The validated ranges were 1.5-300 ng/mL for codeine, norcodeine and morphine, and 23-4,600 ng/mL for C6G, M3G and M6G, with exceptions for norcodeine in muscle (3-300 ng/mL), morphine in muscle, fat and brain (3-300 ng/mL) and M6G in fat (46-4,600 ng/mL). Within-run and between-run accuracy (88.1-114.1%) and precision (CV 0.6-12.7%), matrix effects (CV 0.3-13.5%) and recovery (57.8-94.1%) were validated at two concentration levels; 3 and 150 ng/mL for codeine, norcodeine and morphine, and 46 and 2,300 ng/mL for C6G, M3G and M6G. Freeze-thaw and long-term stability (6 months at -80°C) was assessed, showing no significant changes in analyte concentrations (-12 to +8%). The method was applied in two authentic forensic autopsy cases implicating codeine in both therapeutic and presumably lethal concentration levels.

EtG/EtS in Urine from sexual assault victims determined by UPLC-MS-MS

In cases of sexual assault, victims often present too late for the detection of ethanol in biological samples. An ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS-MS) method was developed and validated for the determination of ethyl glucuronide (EtG) and ethyl sulfate (EtS) in urine. Sample preparation prior to UPLC-MS-MS analysis was a simple sample dilution. The calibration ranges were 0.2-20 mg/L, and between-assay relative standard deviations were in the range of 0.7-7.0% at concentrations of 0.3, 3.0 and 7.0 mg/L. Urine samples were analyzed from 59 female patients presenting to the Sexual Assault Centre at St. Olav University Hospital in Trondheim, Norway between November 2010 and October 2011. EtG and EtS results were fully concordant, and positive in 45 of the 48 cases with self-reported alcohol intake. In contrast, ethanol was detectable in only 20 of these cases, corresponding to sensitivities of 94 and 42%, respectively. Of the patients reporting no alcohol intake, none had positive EtG/EtS findings. These data show that analysis of EtG and EtS greatly increases the detection window of alcohol ingestion in cases of sexual assault, and may shed additional light on the involvement of ethanol in such cases. The victims' self-reported intake of alcohol seems to be reliable in this study, according to the EtG/EtS findings.

Challenges to antagonist blockade during sustained-release naltrexone treatment

AIMS

Naltrexone is a competitive opioid antagonist that effectively blocks the action of heroin and other opioid agonists. Sustained-release naltrexone formulations are now available that provide long-acting opioid blockade. This study investigates the use of heroin and other opioids among opioid-dependent patients receiving treatment with long-acting naltrexone implants, their subjective experience of drug 'high' after opioid use, and factors associated with opioid use.

METHODS

Participants (n = 60) were opioid-dependent patients receiving treatment with naltrexone implants. Outcome data on substance use, drug 'high', depression and criminal activity were collected over a 6-month period. Blood samples were taken to monitor naltrexone plasma levels, and hair samples to verify self-reported opioid use.

FINDINGS

More than half [n = 34 or 56%; 95% confidence interval (CI) 44-68%)] the patients challenged the blockade with illicit opioids during the 6-month treatment period; 44% (n = 26; 95% CI 32-56%) were abstinent from opioids. Mean opioid use was reduced from 18 [standard deviation (SD)13] days during the month preceding treatment to 6 days (SD 11) after 6 months. Of the respondents questioned on opioid 'high' (n = 31), nine patients (30%; 95% CI 16-47%) reported partial drug 'high' following illicit opioid use, and three (12%; 95% CI 3-26%) reported full 'high'. Opioid use was associated with use of non-opioid drugs and criminal behaviour.

CONCLUSIONS

Challenging naltrexone blockade with heroin on at least one occasion is common among sustained-release naltrexone patients, but only a minority of patients use opioids regularly. Challenges represent a warning sign for poor outcomes and often occur in the context of polydrug use and social adjustment problems.

Retention in naltrexone implant treatment for opioid dependence

BACKGROUND

Naltrexone's usefulness in the treatment of opioid dependence stems from its ability to block the action of heroin and other opioids. However, many patients are ambivalent towards naltrexone and often drop out of treatment with orally administered naltrexone. Sustained release naltrexone seems promising in reducing opioid use, but the extent to which patients remain in treatment beyond the first dosage of naltrexone is not clear.

METHODS

Patients (n=61) receving treatment with sustained release naltrexone implants were offered a second naltrexone implant after 6 months. Patients who remained in treatment were compared to those who did not, on drug use, mental health, and social problems before and during naltrexone implant treatment. Information was obtained on other treatments sought by patients who discontinued naltrexone. Blood samples were used to verify naltrexone release, and hair samples to confirm opioid intake.

RESULTS

Of the patients who received the first naltrexone implant, 51% (n=31) remained in naltrexone implant treatment. Among those who discontinued treatment, 21% expressed a wish to reimplant but failed to attend for reimplantation and 28% declined reimplantation: 6 non-retained patients initiated maintenance or residential treatment. Remaining in naltrexone treatment was related to pre-study length of employment, illicit drug use, and concern for family problems. Higher levels of substance misuse and criminal activity during naltrexone treatment were negatively related to subsequent retention.

CONCLUSION

Rates of retention among opioid-dependent patients receiving naltrexone implant treatment are encouraging and support this as a feasible long-term treatment option.

Determination of ethylglucuronide in oral fluid by ultra-performance liquid chromatography- tandem mass spectrometry

An ultra-performance liquid chromatography-tandem mass spectrometry method has been developed and validated for the determination of ethylglucuronide (EtG) in oral fluid. Sample clean-up was achieved by solid-phase extraction with a Hyper-SEP SAX column. Negative ionization was performed in the multiple reaction monitoring mode. Two transitions were monitored for the analyte and one for the internal standard EtG-d(5). The calibration range was 4.4-222 ng/mL. The recovery of the analyte ranged from 86 to 99%, and the between-assay precisions ranged from 5 to 9% RSD. The limit of quantification was found to be 4.4 ng/mL. The concentration of EtG in oral fluid collected 2-14 h after a moderate alcohol intake varied from 13.3 to 57.7 ng/mL.

Naltrexone implants after in-patient treatment for opioid dependence: randomised controlled trial

BACKGROUND

Naltrexone has considerable potential in helping to prevent relapse in heroin dependency. A longer-lasting formulation for naltrexone treatment is desirable to further reduce non-adherence and relapse during treatment of opiate dependence.

AIMS

To evaluate the safety and effectiveness of a 6-month naltrexone implant in reducing opioid use after in-patient treatment.

METHOD

A group of 56 abstinence-oriented patients who completed in-patient treatment for opioid dependence were randomly and openly assigned to receive either a 6-month naltrexone implant or their usual aftercare. Drug use and other outcomes were assessed at 6-month follow-up.

RESULTS

Patients receiving naltrexone had on average 45 days less heroin use and 60 days less opioid use than controls in the 180-day period (both P<0.05). Blood tests showed naltrexone levels above 1 ng/ml for the duration of 6 months. Two patients died, neither of whom had received an implant.

CONCLUSIONS

Naltrexone implant treatment safely and significantly reduces opioid use in a motivated population of patients.

Drug screening of hair by liquid chromatography-tandem mass spectrometry

Hair has become an important matrix for drug analysis, complementary to blood and urine as a matrix. A prolonged detection window makes hair analysis suitable for the detection of exposure to illegal and medicinal drugs for periods up to 12 months. In the present study, a liquid chromatography-tandem mass spectrometry (LC-MS-MS) method for drug screening in hair was developed and validated. To 20 mg of hair, 0.45 mL of acetonitrile/25 mM formic acid (5:95 v/v) and 50 microL of deuterated internal standards were added, and the sample was incubated in a water bath at 37 degrees C for 18 h. LC separation was achieved with a Zorbax SB-Phenyl column (2.1 x 100 mm, 3.5-microm particle). Mass detection was performed by positive ion mode electrospray LC-MS-MS and included the following drugs/metabolites: nicotine, cotinine, morphine, 6-monoacetylmorphine, codeine, amphetamine, methamphetamine, 3,4-methylenedioxymeth-amphetamine, cocaine, benzoylecgonine, 7-aminonitrazepam, 7-aminoclonazepam, 7-aminoflunitrazepam, oxazepam, diazepam, alprazolam, zopiclone, zolpidem, carisoprodol, meprobamate, buprenorphine, and methadone. Within- and between-assay relative standard deviations varied from 2.0% to 12% and 2.7% to 15%, respectively. The accuracies were in the range of -24% to 16%, and recoveries ranged from 25% to 100%. The LC-MS-MS method proved to be simple and robust for the determination of drugs in hair. It has been used for authentic samples in our laboratory in the past year.

[Determination of buprenorphine in urine]

Buprenorphine is one of the drugs used for treatment of opioid-dependent patients enrolled in rehabilitation programs in Norway. Buprenorphine is metabolized in the liver by cytochrome P450 to the active metabolite norbuprenorphine, and further to buprenorphine-glucuronide and norbuprenorphine-glucuronide. The Division of Forensic Toxicology and Drug Abuse at the Norwegian Institute of Public Health has during the past 5 years received an increasing number of urine samples for buprenorphine analysis. All urine samples with question of buprenorphine have since August 2005 been analysed with a new method, which analyses the glucuronides of buprenorphine and norbuprenorphine in urine. This method is fast and simple and saves time and resources in our routine laboratory.

Rapid Quantification of Buprenorphine-Glucuronide and Norbuprenorphine-Glucuronide in Human Urine by LC-MS-MS

A liquid chromatography-tandem mass spectrometry (LC-MS-MS) method was developed and validated for the determination of buprenorphine-glucuronide (BUP-G) and norbuprenorphine-glucuronide (NBUP-G) in human urine. The method included a dilution step followed by filtration through a Mini-Uniprep Filter and direct injection onto the LC column. The analytes were quantified in multiple reactions monitoring mode using one transition ion. Norbuprenorpine-d(3) (NBUP-d(3)) was used as the internal standard. The concentration ranges were 6-161 ng/mL for BUP-G and 12-295 ng/mL for NBUP-G. Recoveries determined after filtration for the analytes were 75%. The between-day precision of the method was in the range of 4.8-11%. The limits of quantification were found to be 4.6 ng/mL for BUP-G and 11.8 ng/mL for NBUP-G. Approximately 1000 samples from law enforcement, prison inmates, probation services, and hospitals were analyzed by the presented method. The ratios of drug glucuronides versus creatinine were calculated for a selection of samples (n = 151), where there was information on treatment with buprenorphine between 16 and 20 mg/day. The majority (86%) of the samples had a ratio of BUP-G/creatinine below 570 microg/g, and 76% of the samples had NBUP-G/creatinine lower than 1060 microg/g. The LC-MS-MS method proved to be robust and specific for the determination of BUP-G and NBUP-G in urine.

Determination of Benzodiazepines in Human Urine using Solid-Phase Extraction and High-Performance Liquid Chromatography-Electrospray Ionization Tandem Mass Spectrometry

A liquid chromatography-tandem mass spectrometry (LC-MS-MS) method has been developed and validated for the determination of benzodiazepines, on the market in Norway, and/or their metabolites in human urine. The following compounds were included: 7-aminonitrazepam, 7-aminoclonazepam, 7-aminoflunitrazepam, alprazolam, alpha-hydroxyalprazolam, oxazepam, 3-OH-diazepam, and n-desmethyldiazepam. The method includes hydrolysis of urine samples (0.5 mL) with beta-glucuronidase at 60 degrees C for 2 h before solid-phase extraction with a polymer-based mixed-mode column. The analytes were quantified in multiple reaction monitoring mode using two transitions. Deuterated analogues were used as internal standards for all analytes except 7-aminonitrazepam and alpha-hydroxyalprazolam, which were quantified using 7-aminoclonazepam-d(4) and alprazolam-d(5), respectively. The concentration range was 0.1-8.0 microM for 7-aminonitrazepam, 7-aminoclonazepam, 7-aminoflunitrazepam, alprazolam, and alpha-hydroxyalprazolam and 0.5-40 microM for the other compounds. The average recovery for the different analytes ranged from 56% to 83%. The between-day precision of the method was in the range of 3-12%. The limits of quantification were found to be between 0.002 and 0.01 microM for the different compounds. Comparison with other analytical methods was performed for method validation, using approximately 500 samples provided by the routine laboratory at the Norwegian Institute of Public Health. The LC-MS-MS method has proven to be robust and specific for the determination of benzodiazepines in urine. It has been routinely used for approximately 1800 samples in the past 7 months.

Incorporation of the food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) into fur and correlation with intestinal tumourigenesis in Min/+ mice

The purpose of this work was to correlate the amount of the food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) determined in mouse fur with the number of intestinal tumours induced by PhIP, to further evaluate incorporation of PhIP into hair as a putative exposure biomarker for food mutagens. We have previously shown that PhIP increases intestinal tumourigenesis in C57BL/6J-Min/+ (Multiple Intestinal Neoplasia) mice. Fur was sampled from mice exposed according to various PhIP protocols, and the amount of PhIP in the fur was quantitated by high performance liquid chromatography - mass spectrometry (HPLC-MS). A quantitative incorporation of PhIP in the fur was demonstrated after a single subcutaneous injection of PhIP, and between one and eight PhIP exposures either via direct subcutaneous injections or through breast milk from PhIP-injected dams. However, after higher exposures, the amount of PhIP in the fur appeared to reach saturation. After low exposures to PhIP, the number of intestinal tumours correlated with the amount of PhIP in the fur of individual mice, whereas after higher exposures, the number of tumours was relatively higher than the amounts of incorporated PhIP in the fur. Other factors, e.g. amounts of reactive PhIP metabolites formed, are also determining the number of intestinal tumours. The demonstrated quantitative incorporation of PhIP into mice fur and the correlation with number of intestinal tumours at the lower exposures, indicate that determination of PhIP in human hair may be a suitable biomarker for exposure to dietary PhIP, which is found in human hair in 10-3 lower amounts than in these mice.

Biomarkers of exposure to heterocyclic amines: approaches to improve the exposure assessment

Various methods of exposure assessment, such as questionnaires, sometimes combined with pictures of cooked meat, have been employed in investigations on the relationship between heterocyclic amines (HA) and health effects. However, as the content of heterocyclic amines vary greatly with cooking conditions, it is difficult to obtain an accurate estimate of the exposure. To improve the exposure assessment, the use of biomarkers has been investigated. The metabolism of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is well characterised. In humans, the major part of the dose is excreted in urine within 24-48 h following a meal. A few percent is excreted as parent compounds, whereas the major part is metabolites. Urinary level of parent HA reflects only recent exposure. However, the pattern of excreted metabolites might indicate the capacity to activate or detoxify HAs. The excretion of glucuronide conjugates of N-hydroxy-PhIP and N-hydroxy-MeIQx could be a marker for the N-hydroxylation capacity and the dose of the proximate metabolites. Recently, we proposed 5-OH-PhIP as a marker for the ultimate reactive metabolite of PhIP, since it is formed from this compound as a by-product along with the formation of PhIP-DNA adducts. In a search for biomarkers reflecting exposure over some time, blood protein adducts with a longer lifespan have been investigated, and PhIP adducts of serum albumin and haemoglobin from meat-consuming humans were recently reported. Many compounds, like drugs, nicotine and narcotics, bind to melanin in hair and give information on exposure for longer time periods. In mice, PhIP is irreversibly incorporated in a dose-dependent manner into hair, and in humans exposed to an ordinary diet, it was found to vary from <50 to 5000 pg PhIP/g hair. The incorporation is also dependent on the content of eumelanin. The use of PhIP in hair as a biomarker of exposure is promising, but needs validation, using other methods of exposure assessment.

Characterization of metabolites of benz(j)aceanthrylene in faeces, urine and bile from rat

1. The excretion of benz[j]aceanthrylene (B[j]A) and the biotransformation products found in faeces, urine and bile of rat exposed to [3H]-labelled B[j]A have been studied. 2. About 95% of the administered radioactivity was excreted within 7 days, 79% via faeces and 16% via urine, and most of the radioactivity in urine and faeces was excreted within 2 days. 3. The B[j]A metabolites excreted between days 1 and 2, including those excreted in bile during the first 5.5 h in a separate experiment, were further characterized by HPLC, UV and electrospray/atmospheric pressure chemical ionization mass spectrometry. 4. In faeces, bile and urine, hydroxylated B[j]A metabolites predominated. The major metabolites in faeces were B[j]A-1,2-dihydrodiol-8-hydroxy and B[j]A-1,2-dihydrodiol-10-hydroxy. These metabolites were found as conjugated metabolites in the bile. The glucuronide conjugate of B[j]A-1,2-dihydrodiol-10-hydroxy was also a major metabolite in urine. Two sulphate conjugates of oxidized B[j]A were detected in bile, a sulphate conjugate of a B[j]A-dihydrodiol-phenol and B[j]A-1,2-dihydrodiol-10-sulphate. Trans-B[j]A-1,2-dihydrodiol was detected in urine, faeces and bile. 5. These findings support the hypothesis that epoxidation at the cyclopenta ring is an important biotransformation pathway for B[j]A in vivo. In addition to the characterized metabolites, a large fraction of polar compounds, possibly glutathione conjugates, was also excreted in urine and bile.