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Owing to the lack of an internationally recognized tacrolimus reference material and reference method, current LC-MS and immunoassay test methods used to monitor tacrolimus concentrations in whole blood are not standardized. The aim of this study was to assess the need for tacrolimus assay standardization.

We sent a blinded 40-member whole-blood tacrolimus proficiency panel (0–30 μg/L) to 22 clinical laboratories in 14 countries to be tested by the following assays: Abbott ARCHITECT (n = 17), LC-MS (n = 9), and Siemens Dade Dimension (n = 5). Selected LC-MS laboratories (n = 4) also received a common calibrator set. We compared test results to a validated LC-MS method. Four samples from the proficiency panel were assigned reference values by using exact-matching isotope-dilution mass spectrometr at LGC.

The range of CVs observed with the tacrolimus proficiency panel was as follows: LC-MS 11.4%–18.7%, ARCHITECT 3.9%–9.5%, and Siemens Dade 5.0%–48.1%. The range of historical within-site QC CVs obtained with the use of 3 control concentrations were as follows: LC-MS low 3.8%–10.7%, medium 2.0%–9.3%, high 2.3%–9.0%; ARCHITECT low 2.5%–9.5%, medium 2.5%–8.6%, high 2.9%–18.6%; and Siemens/Dade Dimension low 8.7%–23.0%, medium 7.6%–13.2%, high 4.4%–10.4%. Assay bias observed between the 4 LC-MS sites was not corrected by implementation of a common calibrator set.

Tacrolimus assay standardization will be necessary to compare patient results between clinical laboratories. Improved assay accuracy is required to provide optimized drug dosing and consistent care across transplant centers globally.

3,4-Methylendioxymethamphetamine (MDMA) is excreted inhuman urine as unchanged drug and phase I and II metabolites. Previousurinary excretion studies after controlled oral MDMA administrationhave been performed only after conjugate cleavage. Therefore, weinvestigated intact MDMA glucuronide and sulfate metaboliteexcretion.

We used LC–high-resolution MS and GC-MS to reanalyze blind urinesamples from 10 participants receiving 1.0 or 1.6 mg/kg MDMAorally. We determined median C_max,t_max, first and last detection times, and totalurinary recovery; calculated ratios of sulfates and glucuronides; andperformed in vitro–in vivo correlations.

Phase II metabolites of 3,4-dihydroxymethamphetamine (DHMA),4-hydroxy-3-methoxymethamphetamine (HMMA),3,4-dihydroxyamphetamine (DHA), and4-hydroxy-3-methoxyamphetamine were identified, although onlyDHMA sulfates, HMMA sulfate, and HMMA glucuronide had substantialabundance. Good correlation was observed for HMMA measured after acidhydrolysis and the sum of unconjugated HMMA, HMMA glucuronide, and HMMAsulfate (R² = 0.87). More than 90% oftotal DHMA and HMMA were excreted as conjugates. The analyte with thelongest detection time was HMMA sulfate. Median HMMAsulfate/glucuronide and DHMA 3-sulfate/4-sulfate ratios for the first24 h were 2.0 and 5.3, respectively, in accordance with previousin vitro calculations from human liver microsomes and cytosolexperiments.

Human MDMA urinary metabolites are primarily sulfates and glucuronides,with sulfates present in higher concentrations than glucuronides. Thisnew knowledge may lead to improvements in urine MDMA and metaboliteanalysis in clinical and forensic toxicology, particularly for theperformance of direct urine analysis.

Oral fluid (OF) testing is increasingly important for drug treatment, workplace, and drugged-driving programs. There is interest in predicting plasma or whole-blood concentrations from OF concentrations; however, the relationship between these matrices is incompletely characterized because of few controlled drug-administration studies.

Ten male daily cannabis smokers received around-the-clock escalating 20-mg oral ⁹-tetrahydrocannabinol (THC, dronabinol) doses (40–120 mg/day) for 8 days. Plasma and OF samples were simultaneously collected before, during, and after dosing. OF THC, 11-hydroxy-THC and 11-nor-9-carboxy-THC (THCCOOH) were quantified by GC-MS at 0.5-μg/L, 0.5-μg/L, and 7.5-ng/L limits of quantification (LOQs), respectively. In plasma, the LOQs were 0.25 μg/L for THC and THCCOOH, and 0.5 μg/L for 11-hydroxy-THC.

Despite multiple oral THC administrations each day and increasing plasma THC concentrations, OF THC concentrations generally decreased over time, reflecting primarily previously self-administered smoked cannabis. The logarithms of the THC concentrations in oral fluid and plasma were not significantly correlated (r = –0.10; P = 0.065). The OF and plasma THCCOOH concentrations, albeit with 1000-fold higher concentrations in plasma, increased throughout dosing. The logarithms of OF and plasma THCCOOH concentrations were significantly correlated (r = 0.63; P < 0.001), although there was high interindividual variation. A high OF/plasma THC ratio and a high OF THC/THCCOOH ratio indicated recent cannabis smoking.

OF monitoring does not reliably detect oral dronabinol intake. The time courses of THC and THCCOOH concentrations in plasma and OF were different after repeated oral THC doses, and high interindividual variation was observed. For these reasons, OF cannabinoid concentrations cannot predict concurrent plasma concentrations.

⁹-Tetrahydrocannabinol (THC) is the most frequently observed illicit drug in investigations of accidents and driving under the influence of drugs. THC-glucuronide has been suggested as a marker of recent cannabis use, but there are no blood data following controlled THC administration to test this hypothesis. Furthermore, there are no studies directly examining whole-blood cannabinoid pharmacokinetics, although this matrix is often the only available specimen.

Participants (9 men, 1 woman) resided on a closed research unit and smoked one 6.8% THC cannabis cigarette ad libitum. We quantified THC, 11-hydroxy-THC (11-OH-THC), 11-nor-9-carboxy-THC (THCCOOH), cannabidiol (CBD), cannabinol (CBN), THC-glucuronide and THCCOOH-glucuronide directly in whole blood and plasma by liquid chromatography/tandem mass spectrometry within 24 h of collection to obviate stability issues.

Median whole blood (plasma) observed maximum concentrations (C_max) were 50 (76), 6.4 (10), 41 (67), 1.3 (2.0), 2.4 (3.6), 89 (190), and 0.7 (1.4) µg/L 0.25 h after starting smoking for THC, 11-OH- THC, THCCOOH, CBD, CBN, and THCCOOH-glucuronide, respectively, and 0.5 h for THC-glucuronide. At observed C_max, whole-blood (plasma) detection rates were 60% (80%), 80% (90%), and 50% (80%) for CBD, CBN, and THC-glucuronide, respectively. CBD and CBN were not detectable after 1 h in either matrix (LOQ 1.0 µg/L).

Human whole-blood cannabinoid data following cannabis smoking will assist whole blood and plasma cannabinoid interpretation, while furthering identification of recent cannabis intake.