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Phosphatidylethanol (PEth) is a non‐oxidative metabolite of alcohol (ethanol), which is a sensitive and specific indicator of historic ethanol consumption. Although PEth production from ethanol is catalysed by the ubiquitous enzyme phospholipase D, it resides mainly within the erythrocyte compartment of the blood. PEth analysis has been reported in different preparations of whole blood, representing one of the barriers of inter‐laboratory comparisons. We previously reported that expressing PEth concentrations in terms of blood erythrocyte content is more sensitive than whole blood volume, and haematocrit‐corrected liquid whole blood calculations of erythrocyte PEth and isolated erythrocyte PEth concentrations are comparable when assayed under identical analytical conditions. Acceptance of a clinical diagnostic assay by accreditation bodies requires proficiency testing with a third‐party analytical facility. To explore different blood preparations within the same inter‐laboratory program, 60 matched isolated erythrocyte or liquid whole blood specimens were tested at three laboratories. Laboratories measured PEth by liquid chromatography‐tandem mass spectrometry (LC‐MS/MS), two using isolated erythrocytes, while the third used liquid whole blood, which underwent haematocrit correction before comparison with isolated erythrocyte PEth concentrations. There was acceptable consensus (87%) among laboratories to detect PEth around a cut‐off of 35 μg/L of erythrocytes. Each laboratory correlated well with the group average PEth concentration (R > 0.98) for each specimen above the cut‐off. Differences were observed between laboratories in bias, which did not affect comparable sensitivity at the selected cut‐off. This work demonstrates the feasibility of an inter‐laboratory comparison for erythrocyte PEth analysis across different LC‐MS/MS methodologies and different blood preparations. [ABSTRACT FROM AUTHOR]

Phosphatidylethanol (PEth) forms in erythrocyte membranes after alcohol consumption, offering a persisting biomarker, that is measurable in whole blood, washed erythrocytes and dried blood spots. For a predominantly erythrocyte-restricted analyte, erythrocyte concentrations seem to have most validity in patients who are anemic through alcoholism or other pathologies, despite preparation increasing assay complexity. Differences in specimen preparation alter PEth concentrations for the same patient, meaning that criteria for interpreting PEth results should relate to specimen type, presenting a barrier to achieving harmonization. We therefore tested whether erythrocyte PEth might be validly calculated by hematocrit correction of a whole blood PEth measurement. PEth testing primarily serves to distinguish drinkers from non-drinkers. In choosing between specimen types, it is important to compare their utility in separating those two groups. We therefore processed 281 blood samples from 17 non-drinkers and 61 drinkers, to prepare matched whole blood and washed erythrocyte specimens. These were assayed by liquid chromatography–tandem mass spectrometry and compared in identifying alcohol consumption. The erythrocyte PEth concentration in the whole blood specimens was also calculated by correcting whole blood concentration by the specimen's hematocrit, as an alternative to prepare washed erythrocytes. The hematocrit-corrected erythrocyte concentrations were included in these comparisons. Predictably, this work found that sensitivity was consistently better at the lower cut-off of 8 µg/L than at 20 µg/L. Sensitivities were also higher for washed erythrocytes than whole blood, explained by the lower erythrocyte mass in the same volume of whole blood. Hematocrit-corrected whole blood PEth concentrations correlated with erythrocyte concentrations, except for the four highest values, which did not influence comparative sensitivity. Specificity was 100% for washed erythrocytes, whole blood and hematocrit-corrected whole blood at either cut-off because non-drinkers had undetectable PEth. We conclude that hematocrit correction of whole blood PEth concentrations theoretically provides an alternative to the preparation of washed erythrocytes. [ABSTRACT FROM AUTHOR]

Background The fixed dose combination of artemether-lumefantrine (AL) is the most widely used treatment for uncomplicated Plasmodium falciparum malaria. Relatively lower cure rates and lumefantrine levels have been reported in young children and in pregnant women during their second and third trimester. The aim of this study was to investigate the pharmacokinetic and pharmacodynamic properties of lumefantrine and the pharmacokinetic properties of its metabolite, desbutyl-lumefantrine, in order to inform optimal dosing regimens in all patient populations. Methods and findings A search in PubMed, Embase, ClinicalTrials.gov, Google Scholar, conference proceedings, and the WorldWide Antimalarial Resistance Network (WWARN) pharmacology database identified 31 relevant clinical studies published between 1 January 1990 and 31 December 2012, with 4,546 patients in whom lumefantrine concentrations were measured. Under the auspices of WWARN, relevant individual concentration-time data, clinical covariates, and outcome data from 4,122 patients were made available and pooled for the meta-analysis. The developed lumefantrine population pharmacokinetic model was used for dose optimisation through in silico simulations. Venous plasma lumefantrine concentrations 7 days after starting standard AL treatment were 24.2% and 13.4% lower in children weighing Conclusions Our findings suggest that revised AL dosing regimens for young children and pregnant women would improve drug exposure but would require longer or more complex schedules. These dosing regimens should be evaluated in prospective clinical studies to determine whether they would improve cure rates, demonstrate adequate safety, and thereby prolong the useful therapeutic life of this valuable antimalarial treatment., Author(s): Frank Kloprogge 1,2,3, Lesley Workman 4,5, Steffen Borrmann 6,7, Mamadou Tékété 7,8, Gilbert Lefèvre 9, Kamal Hamed 10, Patrice Piola 11, Johan Ursing 12,13,14, Poul Erik Kofoed 14,15, Andreas [...]

Aims: The aim of this study was to assess the pharmacokinetic properties of artemether, lumefantrine and their active metabolites in Plasmodium knowlesi malaria. Methods: Malaysian adults presenting with uncomplicated P. knowlesi infections received six doses of artemether (1.7 mg/kg) plus lumefantrine (10 mg/kg) over 3 days. Venous blood and dried blood spot (DBS) samples were taken at predetermined time‐points over 28 days. Plasma and DBS artemether, dihydroartemisinin, lumefantrine and desbutyl‐lumefantrine were measured using liquid chromatography‐mass spectrometry. Multi‐compartmental population pharmacokinetic models were developed using plasma with or without DBS drug concentrations. Results: Forty‐one participants (mean age 45 years, 66% males) were recruited. Artemether‐lumefantrine treatment was well tolerated and parasite clearance was prompt. Plasma and DBS lumefantrine concentrations were in close agreement and were used together in pharmacokinetic modelling, but only plasma concentrations of the other analytes were used because of poor correlation with DBS levels. The areas under the concentration–time curve (AUC0–∞) for artemether, dihydroartemisinin and lumefantrine (medians 1626, 1881 and 625 098 μg.h/L, respectively) were similar to those reported in previous pharmacokinetic studies in adults and children. There was evidence of auto‐induction of artemether metabolism (mean increase in clearance relative to bioavailability 25.2% for each subsequent dose). The lumefantrine terminal elimination half‐life (median 9.5 days) was longer than reported in healthy volunteers and adults with falciparum malaria. Conclusion: The disposition of artemether, dihydroartemisinin and lumefantrine in knowlesi malaria largely parallels that in other human malarias. DBS lumefantrine concentrations can be used in pharmacokinetic studies but DBS technology is currently unreliable for the other analytes. [ABSTRACT FROM AUTHOR]