Competitive dopamine receptor antagonists increase the equiactive cocaine concentration during self-administration.

Competitive dopamine receptor antagonists increase the rate of cocaine self-administration. As the rate of self-administration at a particular unit dose is determined by the satiety threshold and the elimination half-life (t(½)) of cocaine, we investigated whether dopamine receptor antagonists altered these parameters in rats. The plasma cocaine concentration at the time of each self-administration was constant during a session demonstrating that this satiety threshold concentration represents an equiactive cocaine concentration. The plasma cocaine concentration at the time of self-administration was increased by SCH23390, consistent with pharmacological theory. In rats trained to reliably self-administer cocaine, SCH23390 had no effect on the plasma steady-state cocaine concentration produced by constant infusions of cocaine. Therefore, this antagonist had no effect on cocaine t(½) at a dose that accelerated cocaine self-administration. A constant cocaine infusion at a rate that maintained steady state concentrations above the satiety threshold stopped self-administration. SCH23390, or the D2 dopamine receptor antagonist (-)eticlopride, reinstated self-administration in the presence of the constant cocaine infusion. This is consistent with SCH23390 and eticlopride raising the satiety threshold above the steady state level produced by the constant cocaine infusion. It is concluded that the antagonist-induced acceleration of cocaine self-administration is the result of a pharmacokinetic/pharmacodynamic interaction whereby the rate of cocaine elimination is faster at the higher concentrations, as dictated by first-order kinetics, so that cocaine levels decline more rapidly to the elevated satiety threshold. This results in the decreased interinjection intervals.

Interpretation of Pain Management Testing Results Using Case Examples.

BACKGROUND: Because of the increasing volume of opiate-related overdoses, clinical testing of urine for drugs and related compounds in pain management clinics has become increasingly important. Interpreting findings of drugs present in urine specimens requires knowledge of pharmacokinetics, metabolism, drug purity, and cutoff concentrations used to report a positive result. CONTENT: This case-based mini-review provides examples of how to interpret immunoassay and quantitative confirmatory urine drug-testing results. Particular emphasis is placed on interpretation of opiate and benzodiazepine results, as these drugs have complicated metabolic profiles. SUMMARY: Both determining patient medication compliance and identifying the presence of additional drugs provides important information to the treating physician involved in managing pain. Mass spectrometry-based methods are required to identify specific drugs present and can provide important quantitative data for interpreting opiate medication compliance.

A sensitive assay for urinary cocaine metabolite benzoylecgonine shows more positive results and longer half-lives than those using traditional cut-offs.

Cocaine is a common drug of abuse. To detect its use, a screening detection concentration for the cocaine metabolite benzoylecgonine is commonly set at 150 ng/mL and its confirmatory cut-off is set at 100 ng/mL. Studies have suggested that these cut-offs may be set too high, allowing some patients with this substance abuse problem to be missed or improperly monitored. With the advent of liquid chromatography-tandem mass spectrometry (LC-MS/MS) technology it is possible to reliably detect and quantify lower concentrations of its metabolite benzoylecgonine as part of a larger drug panel. One purpose of the study was to establish if there was a significant increase in detection of cocaine use with a ten-fold more sensitive cut-off. A very sensitive dilute and shoot assay for benzoylecgonine was developed with a lower limit of quantitation of 5 ng/mL. Validation of the 5 ng/mL cut-off was achieved by plotting all the positive cocaine observations as a frequency distribution on a logarithmic scale. The number of positive results with measurable concentrations below the typical industry 100 ng/mL cut-off level but above the high sensitivity 5 ng/mL cut-off level was observed to be 51.9% of the observed positives. The lower cut-off also allowed a re-evaluation of the window of detection after cessation of use. It was observed to be between 17 and 22 days. © 2016 Precision Diagnostics, LLC. Drug Testing and Analysis published by John Wiley & Sons, Ltd.

Reference intervals: an update.

Reference intervals serve as the basis of laboratory testing and aid the physician in differentiating between the healthy and diseased patient. Standard methods for determining the reference interval are to define and obtain a healthy population of at least 120 individuals and use nonparametric estimates of the 95% reference interval. This method is less accurate if the group size is significantly less and does not allow for exclusion of outliers. In order to overcome these limitations many authors in the current literature report reference intervals after arbitrary truncation of the data or use inappropriate parametric calculations. We argue that the use of outlier removal and robust estimators, with or without transformation to normality, address the shortcomings of the standard method and eliminate the need for employing less valid methods.To test these methods of analysis well-defined test groups are required. In a few studies physician-determined health status is provided for each subject along with commonly measured analytes. The NHANES and Fernald studies provide such groups. With such data it is possible to show the range of effects on the reference interval width by including a known non-healthy subgroup. With the NHANES data the effect ranged from negligible to a 30% increase in reference interval width. We found that use of outlier detection with the robust estimator yielded reference intervals that were closer to those of the true healthy group.Another issue is one of demographics. That is, whether or not one should derive separate reference intervals for different demographic groups, e.g., males and females. The standard mathematical test for deriving separate reference intervals is due to Harris and Boyd. Using the NHANES data we examined 33 analytes for each of three ethnic groups (separated by genders). We used the Harris and Boyd procedure and observed that it was necessary to derive separate reference intervals for approximately 30% of the comparisons. The most notable analytes were glucose and gamma GT.The methods used by most laboratories have similar precision, identical units, are linearly related (often on a 1:1 basis) and correlate well with each other. As a result the only difference is the method bias. By using the reference interval width, this bias is eliminated. We argue that the log ratio of the reference interval widths is a good estimate of the variability between groups.

Urine drug screening in the medical setting.

BACKGROUND: The term drug screen is a misnomer since it implies screening for all drugs, which is not possible. Current practice is to limit the testing to the examination of serum for several drugs such as ethanol, acetaminophen, salicylate, and of urine for several specific drugs or classes of drugs. In the emergency setting the screen should be performed in less than one hour. Controversies continue to exist regarding the value of urine drug testing in the medical setting. The reasons for these include the drugs involved, the sample, the methods utilized to perform the tests, and the level of understanding of the physician using the data, all of which are closely related to the other. METHODS: Current automated methods provide rapid results demanded in emergency situations, but are often designed for, or adapted from, workplace testing and are not necessarily optimized for clinical applications. Furthermore, the use of these methods without consideration of the frequency in which the drugs are found in a given area is not cost-effective. The laboratory must understand the limitations of the assays used and provide this information to the physician. Additionally, the laboratory and the physicians using the data must cooperate to determine which drugs are appropriate and necessary to measure for their institution and clinical setting. In doing so it should be remembered that for many drugs, the sample, urine, contains the end product(s) of drug metabolism, not the parent drug. Furthermore, it is necessary to understand the pharmacokinetic parameters of the drug of interest when interpreting data. Finally, while testing for some drugs may not appear cost-effective, the prevention or reduction of morbidity and mortality may offset any laboratory costs. CONCLUSIONS: While the literature is replete with studies concerning new methods and a few regarding physician understanding, there are none that we could find that thoroughly, objectively, and fully addressed the issues of utility and cost-effectiveness.

Coenzyme Q10 changes are associated with metabolic syndrome.

BACKGROUND: The purpose of this study was to determine whether coenzyme Q10 (CoQ) concentrations and redox status are associated with components of the metabolic syndrome. METHODS: This is a cross-sectional survey of 223 adults (28-78 years), who were drawn from the ongoing Princeton Follow-up Study in greater Cincinnati. Individuals were assessed for measures of fatness, blood pressure, glucose, lipid profiles, C-reactive protein (CRP), reduced CoQ (ubiquinol), oxidized CoQ (ubiquinone), total CoQ and CoQ redox ratio (ubiquinol/ubiquinone). RESULTS: After adjusting for age, sex and race, we found that total CoQ, ubiquinol and CRP levels are significantly increased in metabolic syndrome. Comparison of minimal risk and high-risk metabolic syndrome groups indicates an increased CoQ redox ratio in the high risk group (p<0.05). Step-wise logistic regression analysis, using age, sex, race, (ln)CRP, total cholesterol, LDL, ubiquinol, ubiquinone and total CoQ as predictors, shows that only age (p=0.001), total CoQ adjusted for plasma lipids (p<0.0001) and (ln)CRP (p<0.005) were significant predictors of metabolic syndrome. CONCLUSIONS: The presence of metabolic syndrome components are associated with increased plasma total CoQ and ubiquinol concentrations after adjusting for age, sex and race. An increase in CoQ redox ratio may indicate a gender-specific adaptive response to oxidative stress in females, but not males.

Age-related changes in plasma coenzyme Q10 concentrations and redox state in apparently healthy children and adults.

BACKGROUND: Coenzyme Q10 (CoQ) is an endogenous enzyme cofactor, which may provide protective benefits as an antioxidant. Because age-related CoQ changes and deficiency states have been described, there is a need to establish normal ranges in healthy children. The objectives of this study are to determine if age-related differences in reduced CoQ (ubiquinol), oxidized CoQ (ubiquinone), and CoQ redox state exist in childhood, and to establish reference intervals for these analytes in healthy children. METHODS: Apparently healthy children (n=68) were selected from individuals with no history of current acute illness, medically diagnosed disease, or current medication treatment. Self-reported healthy adults (n=106) were selected from the ongoing Princeton Follow-up Study in greater Cincinnati. Participants were assessed for lipid profiles, ubiquinol concentration, ubiquinone concentration, total CoQ concentration, and CoQ redox ratio. RESULTS: Mean total CoQ and ubiquinol concentrations are similar in younger children (0.2-7.6 years) and adults (29-78 years); however, lipid-adjusted total CoQ concentrations are significantly increased in younger children. Also CoQ redox ratio is significantly increased in younger and older children compared with adults. CONCLUSIONS: Elevated CoQ and redox ratios in children may be an indication of oxidative stress effects, which are associated with early development of coronary heart disease.

Plasma coenzyme Q10 reference intervals, but not redox status, are affected by gender and race in self-reported healthy adults.

BACKGROUND: Abnormal concentrations of coenzyme Q(10) have been reported in many patient groups, including certain cardiovascular, neurological, hematological, neoplastic, renal, and metabolic diseases. However, controls in these studies are often limited in number, poorly screened, and inadequately evaluated statistically. The purpose of this study is to determine the reference intervals of plasma concentrations of ubiquinone-10, ubiquinol-10, and total coenzyme Q(10) for self-reported healthy adults. METHODS: Adults (n=148), who were participants in the Princeton Prevalence Follow-up Study, were identified as healthy by questionnaire. Lipid profiles, ubiquinone-10, ubiquinol-10, and total coenzyme Q(10) concentrations were measured in plasma. The method used to determine the reference intervals is a procedure incorporating outlier detection followed by robust point estimates of the appropriate quantiles. RESULTS: Significant differences between males and females were present for ubiquinol-10 and total coenzyme Q(10). Blacks had significantly higher Q(10) measures than whites in all cases except for the ubiquinol-10/total Q(10) fraction. CONCLUSIONS: The fraction of ubiquinol-10/total coenzyme Q(10) is a tightly regulated measure in self-reported healthy adults, and is independent of sex and racial differences. Different reference intervals for certain coenzyme Q(10) measures may need to be established based upon sex and racial characteristics.

Therapeutic monitoring of benzodiazepines in the management of pain: current limitations of point of care immunoassays suggest testing by mass spectrometry to assure accuracy and improve patient safety.

BACKGROUND: Concomitant use of opioids and benzodiazepines can result in significant untoward effects. Point of care (POC) urine testing devices are commonly used tools to monitor patient use of medications. These useful devices are relatively inexpensive and yield immediate results that can be acted upon at the time of the appointment, although numerous limitations have been identified for specific medications or medication classes. We established the diagnostic accuracy of a commonly used POC testing method for benzodiazepines. METHODS: One thousand patients, from a single interventional pain practice receiving opioid therapy provided urine specimens as part of the usual practice of monitoring consistency with prescribed medications. These de-identified urine specimens were tested using LC-MS/MS and the results were compared using the standard calculations for sensitivity, specificity, and predicted value. Five specimens were excluded from the study because the prescribed flurazepam could not be confirmed by LC-MS/MS (the LC-MS/MS instrumentation was not set to identify flurazepam), resulting in 995 specimens. RESULTS: Point of care assays yielded false negative results for patients prescribed benzodiazepines nearly 20% of the time (98 out of 498 patients). The point of care cup often failed to produce positive results for persons who were shown by LC-MS/MS to be taking lorazepam or clonazepam. Although only 26 out of 498 patients (5%) were prescribed ≥2 benzodiazepines, 73 out of 498 patients (15%) were found to be positive for that drug class. CONCLUSIONS: POC immunoassay for benzodiazepines could fail to provide accurate information regarding patient specific medication use. The false positive and false negative rates of the immunoassay were particularly high for clonazepam and lorazepam. Further testing of patient specimens using more accurate methods such as LC-MS/MS is necessary to provide definitive data that can assist in clinical decision making, and potentially protect these patients from untoward effects, morbidity and mortality.

Observations on the urine metabolic ratio of oxymorphone to oxycodone in pain patients.

The object of this study was to evaluate the metabolism of oxycodone to oxymorphone in a pain patient population using a quantitative liquid chromatography-tandem mass spectrometry analysis of 32,656 urine specimens obtained from pain patients between March 2008 and Feb 2010. The observed excretion was modeled using logarithmic transformation and approximated a Gaussian distribution. Oxycodone excretion into urine had a geometric mean of 1.93 mg/g of creatinine and oxymorphone had a value of 0.41 mg/g of creatinine. Increasing concentrations of oxycodone correlated with a smaller proportion of oxymorphone excretion suggesting saturation of oxycodone metabolism. Urine samples containing oxycodone without oxymorphone allowed an estimation of the proportion of poor metabolizers (2.4 ± 2.1%) in the population. A similar analysis of samples containing oxymorphone without oxycodone gave an estimate of the proportion of ultra-rapid metabolizers (1.8 ± 1.1%) in the population. Samples with concentrations of oxycodone above 10 mg/g of creatinine showed a sub-population of subjects with metabolic ratios roughly 100-fold less than the linear predictive model in this study. This study describes typical ranges for oxycodone and oxymorphone in urine, and showed that it is possible to identify fast or slow metabolizers who may be at risk for adverse events.

Evaluating the relationship between carisoprodol concentrations and meprobamate formation and inter-subject and intra-subject variability in urinary excretion data of pain patients.

Using urinary carisoprodol data from pain patients, our objectives were to determine the relationship between carisoprodol concentration and its conversion to meprobamate, and quantify the intra-subject and inter-subject variability in carisoprodol metabolism. Liquid chromatography-tandem mass spectrometry was used to quantitate carisoprodol and meprobamate concentrations in urine specimens. The log creatinine-corrected carisoprodol versus log creatinine-corrected meprobamate showed a marginal positive relationship (R(2) = 0.395), with a 29.1-fold variance between subjects at the mean carisoprodol concentration. The geometric mean carisoprodol and meprobamate urine concentrations were 0.519 ± 3.38 mg and 28.2 ± 2.34 mg analyte per gram creatinine, respectively. The log metabolic ratio (MR) versus log creatinine-corrected carisoprodol displayed a marginal positive correlation. A subpopulation of outliers with higher carisoprodol and lower meprobamate levels were considered poor metabolizers and represented 0.483% (n = 21) of the study population. Using a curve-fit mathematical model, we estimated 0.318% (n = 10) to be ultra-rapid metabolizers. The inter-subject population geometric standard deviation (SD) of the MR was 3.64. The intra-subject geometric median and mean SD of the MR were 1.60 (interquartile range: 1.28, 2.07) and 1.72 ± 1.60, respectively. Inter-subject variability was 2.27 times greater than the median intra-subject variability. With a better understanding of urine carisoprodol and meprobamate concentrations and variability, urine drug testing provides a useful monitoring reference for clinicians.

Evaluating the relationship of methadone concentrations and EDDP formation in chronic pain patients.

Methadone is used to treat moderate to severe pain in patients not responsive to non-narcotic analgesics and for maintenance treatment of opioid addiction. Methadone is primarily metabolized by N-demethylation to an inactive metabolite 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidene (EDDP) by CYP3A4 and CYP2B6. Establishing expected concentrations for metabolism of methadone to EDDP using urine excretion data may be useful for monitoring "medications" and toxicity. Urine specimens from chronic pain patients were collected during routine clinic visits. Methadone and EDDP were quantified by liquid chromatography-tandem mass spectrometry. Approximately 8,000 subjects who reported taking methadone had creatinine concentrations ≥20 mg/dL, and excreted concentrations of methadone and EDDP above ≥100 ng/mL were selected. The median methadone urine concentration was 3.03 mg/g cr. Ninety-five percent of the population had concentrations between 0.175 and 20.9 mg/g cr. EDDP was, on average, twice the methadone concentration. The wide variance in relationship of methadone to its metabolite was not concentration-dependent. Variability between subjects was larger than variability within subjects. As the urinary pH increased, the proportion of excreted EDDP increased, implying a preferred excretion of EDDP.

Observations on the metabolism of morphine to hydromorphone in pain patients.

Morphine is one of several opioids used to treat chronic pain. Because of its high abuse potential, urine drug tests can confirm "consistency with prescribed medications." Hydromorphone is a recently described minor metabolite of morphine, but few data exist on the characteristics of this metabolic pathway or the relationship of morphine and hydromorphone between and within subjects. Part I of this retrospective study shows that formation of hydromorphone from morphine is concentration-dependent and possibly saturated at high concentrations of morphine. In addition, the percentage of ultra-rapid metabolizers and poor metabolizers can be determined using the lower asymptote of a sigmoidal mathematical fit and are estimated to be 0.63 and 4.0%, respectively. Expected limits of morphine and hydromorphone (as a result of morphine metabolism) concentrations in the urine were established. Part II of this study used the metabolic ratio (hydromorphone-morphine) to determine the inter-patient and intra-patient variability in morphine metabolism to hydromorphone. Metabolic ratio values varied over a large range; 25-fold and 7-fold, respectively. The expected limits established in this study can assist in assessing the cause for possible variances in metabolism, such as drug interactions. The wide variability between and within subjects may explain unpredictable, adverse effects.

Relationship between the concentration of hydrocodone and its conversion to hydromorphone in chronic pain patients using urinary excretion data.

Hydrocodone in combination with acetaminophen is commonly used to control moderate pain and is metabolized by cytochrome P4502D6 to form the active metabolite, hydromorphone. The purpose of this study was to determine the metabolic relationship and variability between hydrocodone and its conversion to hydromorphone using urinary excretion data from chronic pain patients. Liquid chromatography-tandem mass spectrometry was used to quantitate hydrocodone and hydromorphone concentrations in urine specimens. The first visits of 25,200 subjects who took hydrocodone and not hydromorphone and had measurable concentrations were included in this study. The geometric mean (95% confidence index) of hydrocodone and hydromorphone urine concentrations were 1.39 (1.37-1.41) mg per gram of creatinine and 0.224 (0.221-0.227) mg per gram of creatinine, respectively. The log of creatinine-corrected hydromorphone versus the log of creatinine-corrected hydrocodone showed a positive relationship (R(2) = 0.20), with 60-fold variability between subjects. The plot of the log of the metabolic ratio ([hydromorphone] divided by [hydrocodone]) versus the log of creatinine-corrected hydrocodone had a coefficient of determination of R(2) = 0.42, with 125-fold variability between subjects. Ultra-rapid metabolizers represented 0.6% of the population, whereas 4% were poor metabolizers. Within-subject variability for the excretion of hydrocodone in urine was 23-fold, whereas between-subject variability was 134-fold. Hydrocodone and hydromorphone urine concentrations showed great variability within and between subjects.

Evaluation of high-resolution mass spectrometry for urine toxicology screening in a pain management setting.

To evaluate liquid chromatography-high-resolution mass spectrometry (LC-HR-MS) for urine toxicology screening, 29 analytes were quantitated in 152 urine specimens from patients with chronic pain using two unique mass spectrometry platforms. De-identified specimens were quantitated in April of 2011 by liquid chromatography-triple quadrupole mass spectrometry (LC-MS-MS) and by full-scan LC-HR-MS at Millennium Laboratories. Considering LC-MS-MS as the reference method, false positive results were identified in 19 specimens measured by LC-HR-MS. Application of relative retention times using deuterium labeled internal standards improved the rate of false positive detection to only five specimens, with four occurring for the same analyte. Ultra-high-resolution mass spectrometry (R = 100,000 at m/z 200) showed no improvement over high-resolution mass spectrometry (R = 10,000 at m/z 200) in the number of false positives detected. Quantitative results measured by LC-MS-MS and LC-HR-MS showed good agreement over four orders of dynamic range. This study demonstrates that LC-HR-MS is a suitable platform for toxicology screening for a pain management population and that quantitative accuracy and sensitivity are comparable to that achieved with LC-MS-MS. The specificity of LC-HR-MS is improved by the addition of deuterium labeled internal standards and the implementation of relative retention time matching.

Dilute and shoot: analysis of drugs of abuse using selected reaction monitoring for quantification and full scan product ion spectra for identification.

Our objective was to develop a "dilute and shoot" liquid chromatography-tandem mass spectrometry confirmatory procedure that uses full scan product ion spectra to identify drugs that are present above cutoff values as determined by isotope dilution relative to a deuterium-labeled internal standard. Deuterium-labeled internal standards are added to urine which is then diluted prior to analysis. Full scan product ion spectra were obtained in the data-dependent mode using a linear ion trap (ABI 4000 Qtrap). Identification was based on a purity fit of greater than 70. Ninety-seven urine specimens were analyzed by the method described, and results were compared to values obtained from a reference laboratory using selected reaction monitoring (SRM). The ion trap provided about 30-fold increase in signal-to-noise ratio as compared with the same instrument operated in a traditional full scan product ion mode. The assays were linear to at least 10 times the cutoff. Selecting appropriate triggers for obtaining full scan product ion spectra minimized space charging for specimens that contained high concentrations of drugs. There was 100% concordance between the full scan identification and the SRM results for identification of amphetamine, methamphetamine, benzoylecgonine, morphine, codeine, hydrocodone, and hydromorphone. The ability to "dilute and shoot" reduces the turnaround time for results. The data acquired with SRM and full scan product ion spectra provide accurate quantification and a high degree of specificity.

Anomalous observations of hydrocodone in patients on oxycodone.

BACKGROUND: Urine drug monitoring is used by physicians treating chronic pain patients with opioid therapy. Patients are tested in part to insure that they are not taking other drugs. Therefore, the finding of hydrocodone in a patient who is only prescribed oxycodone has clinical implications. Oxycodone preparations are known to have small amounts of hydrocodone as an impurity estimated to be < 0.1%. We established the concentration of unexpected hydrocodone in patients taking oxycodone. METHODS: Urine drug testing specimens from a population of 30,000 pain patients prescribed oxycodone in various formulations were quantitatively measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The frequency and concentration of hydrocodone as a function of oxycodone concentration were determined. RESULTS: There were 187 specimens with > 100,000 ng/ml of oxycodone. Of these, 72% were positive for hydrocodone. Of the 311 specimens with oxycodone concentrations > 50,000-100,000 ng/ml, 33% were positive for hydrocodone. Of the 1067 specimens with oxycodone > 20,000-50,000 ng/ml, 16% were positive for hydrocodone. Of the 8508 specimens with oxycodone > 1000-20,000 ng/ml, 16% were positive for hydrocodone. CONCLUSIONS: The high frequency of hydrocodone in samples containing high concentrations of oxycodone was ascribed to the manufacturing process of the oxycodone medications. However, a significant number of patients also took hydrocodone that was not listed on their prescribed medications. When oxycodone is > 100,000 ng/ml, hydrocodone should be <1500 ng/ml. When oxycodone is < 100,000 ng/ml then hydrocodone should be <500 ng/ml. Values greater than these indicate non-prescribed hydrocodone use. Clinicians and laboratories testing urine for drugs should be aware of the possibility of low concentrations of hydrocodone in the urine of patients taking high doses of oxycodone.

Ethyl glucuronide, ethyl sulfate, and ethanol in urine after intensive exposure to high ethanol content mouthwash.

To determine the degree of ethanol absorption and the resultant formation and urinary excretion of its conjugated metabolites following intensive use of high ethanol content mouthwash, 10 subjects gargled with Listerine(®) antiseptic 4 times daily for 3» days. First morning void urine specimens were collected on each of the four study days and post-gargle specimens were collected at 2, 4, and 6 h after the final gargle of the study. Urine ethanol, ethyl glucuronide (EtG), ethyl sulfate (EtS), and creatinine were measured. Ethanol was below the positive threshold of 20 mg/dL in all of the urine specimens. EtG was undetectable in all pre-study urine specimens, but two pre-study specimens had detectable EtS (6 and 82 ng/mL; 16 and 83 µg/g creatinine). Only one specimen contained detectable EtG (173 ng/mL; 117 µg/g creatinine). EtS was detected in the urine of seven study subjects, but was not detected in the single specimen that had detectable EtG. The maximum EtS concentrations were 104 ng/mL and 112 µg/g creatinine (in different subjects). Three subjects produced a total of eight (non-baseline) urinary EtS concentrations above 50 ng/mL or 50 µg/g creatinine and three EtS concentrations exceeding 100 ng/mL or 100 µg/g creatinine. In patients being monitored for ethanol use by urinary EtG and EtS concentrations, currently accepted EtG and EtS cutoffs of 500 ng/mL are adequate to distinguish between ethanol consumption and four times daily use of high ethanol content mouthwash.