Limited Sampling Strategies Supporting Individualized Dose Adjustment of Intravenous Busulfan in Children and Young Adults.

BACKGROUND: Therapeutic drug monitoring (TDM) for busulfan supports dose adjustment during conditioning for stem cell transplantation. The authors aimed to develop and validate limited sampling strategies (LSS) of 4-5 samples for a precise estimation of the area under concentration (AUC)-time curve of busulfan, in plasma as an alternative to an intensive sampling strategy (ISS) requiring 9-10 samples. METHODS: ISS TDM data from 297 patients (≤18 years of age) were used. AUCLSS was calculated using the trapezoidal rule and multiple linear regression (MLR). Unlike more complex modeling methods, MLR does not require sophisticated software or advanced training of personnel. MLR coefficients were estimated in the development subset containing randomly selected 50% of the records and were then used to calculate the AUCLSS of the remaining records (the validation subset). The agreement between dose adjustment recommendations (DAR) based on ISS and LSS, in the validation subset, was evaluated by a Bland-Altman analysis. A DAR deviating from an ISS-based reference by <15% was deemed acceptable. RESULTS: Twelve LSSs were acceptable. Sampling at 0, 120, 180, and 240 minutes after the start of the second infusion (LSS15) yielded the best performance, with DAR deviating from the reference by <10% for 95% of cases; the AUCLSS was determined as follows: AUCLSS = 74.7954 × C(0) + 81.8948 × C(120) + 38.1771 × C(180) + 138.1404 × C(240) + 54.1837. This LSS and LSS13 performed similarly well in an independent external validation. CONCLUSIONS: MLR-based estimates of AUCLSS provide DARs that deviate minimally from the reference. LSSs allow the reduction of patient discomfort, a ∼50% reduction of TDM-related workload for nursing staff and blood loss and a ∼25% reduction in laboratory workload. These benefits may encourage wider use of busulfan TDM, supporting safe and efficacious personalized dosing.

Comparison of everolimus QMS immunoassay on Architect ci4100 and liquid chromatography/mass spectrometry: lack of agreement in organ-transplanted patients.

BACKGROUND: Liquid chromatography with mass spectrometry (LC-MS/MS) is the method of choice for the determination of everolimus whole blood concentrations but is not always available. Therefore, immunoassays have been developed for clinical monitoring of everolimus. In previous studies, the Quantitative Microsphere System (QMS) immunoassay had a positive bias compared with LC-MS/MS, but was judged acceptable, although clinical agreement (eg, 95% limits of agreement) was not reported. The objective of this study was to assess whether the agreement between the QMS assay and an LC-MS/MS method was clinically acceptable for use interchangeably in therapeutic everolimus monitoring. METHODS: Whole blood samples from organ-transplanted patients on everolimus therapy were analyzed by both QMS (on Architect ci4100 analyzer) and LC-MS/MS. Paired results were compared using paired Student t test, Bland-Altman plots, and Deming regression analysis. The proportions of falsely supratherapeutic and subtherapeutic results on the QMS assay compared with the LC-MS/MS were calculated. RESULTS: Among 250 samples (169 patients), mean everolimus concentrations determined by LC-MS/MS and QMS assays were 4.8 ± 2.1 ng/mL and 6.3 ± 2.1 ng/mL, respectively (P < 0.001), with 95% lines of agreement between -2.1 and 5.2 ng/mL, a range corresponding to 152% of the mean concentration. When stratified by the type of transplant, a similar positive bias was found in each subgroup (all P < 0.014). Sixty-nine percent of the samples yielding supratherapeutic concentrations (>8 ng/mL) on the QMS assay were within the therapeutic range on the LC-MS/MS. CONCLUSIONS: The everolimus QMS immunoassay, using the Architect ci4100 analyzer, had a significant positive bias compared with LC-MS/MS, with a wide range between the limits of agreement. The lack of agreement may result in inadequate everolimus dose adjustments, suggesting that the QMS assay cannot be used interchangeably with the LC-MS/MS method for therapeutic everolimus monitoring in organ-transplanted patients.

An outbreak of severe coagulopathy in northern Israel among users of illicit synthetic cannabinoids adulterated with brodifacoum.

INTRODUCTION: Adulteration of illicit drugs is a well-known phenomenon that may expose consumers to unexpected adverse effects. We report a large outbreak of severe coagulopathy in northern Israel during nine months in 2021-2022 among users of synthetic cannabinoids adulterated with a long-acting anticoagulant, brodifacoum. METHODS: We performed a retrospective cohort study based on data extracted from the Israeli National Poison Information Center database and from electronic medical patient records at three participating hospitals. Confiscated drug samples and blood samples obtained at admission in a subgroup of patients were tested for the presence of long-acting anticoagulants. RESULTS: We identified 98 patients affected by the outbreak. All patients had a prolonged international normalized ratio on admission, and in 69%, the blood was non-coagulating. For patients treated in the three participating centers (n = 72), the presenting complaint was overt bleeding in 79% of patients, most commonly in the urinary (53%) and gastrointestinal tracts (50%). The most severe complications were intracranial bleeding (4%), hemothorax (3%), pericardial bleeding (1%), and four patients died. Brodifacoum was detected in all available blood samples (median concentration 207 µg/L, interquartile range 112-349 µg/L, range 45-1,118 µg/L), and the drug samples contained both brodifacoum and the synthetic cannabinoid ADB-BUTINACA. All patients were treated with high-dose phytomenadione (vitamin K1) and additionally by packed red blood cell transfusions, fresh frozen plasma, and/or 4-factor prothrombin complex concentrate when indicated. The most frequent phytomenadione (vitamin K1) dose regimen was initially 20 mg intravenously every eight hours, and at discharge, 20 mg orally three times daily. CONCLUSIONS: Outbreaks of severe coagulopathies in users of synthetic cannabinoids adulterated with a long-acting anticoagulant continue to erupt in different regions of the world. Rapid recognition of an outbreak requires a high index of suspicion when confronting young, otherwise healthy subjects with otherwise unexplained severe coagulopathy.