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Background 3-Hydroxypalmitoleoyl-carnitine (C16:1-OH) has recently been reported to be elevated in acylcarnitine profiles of patients with propionic acidemia (PA) or methylmalonic acidemia (MMA) during expanded newborn screening (NBS). High levels of C16:1-OH, combined with other hydroxylated long chain acylcarnitines are related to long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) and trifunctional protein (TFP) deficiency. Methods The acylcarnitine profile of two LCHADD patients was evaluated using liquid chromatography-tandem mass spectrometric method. A specific retention time was determined for each hydroxylated long chain acylcarnitine. The same method was applied to some neonatal dried blood spots (DBSs) from PA and MMA patients presenting abnormal C16:1-OH concentrations. Results The retention time of the peak corresponding to C16:1-OH in LCHADD patients differed from those in MMA and PA patients. Heptadecanoylcarnitine (C17) has been identified as the novel biomarker specific for PA and MMA patients through high resolution mass spectrometry (Orbitrap) experiments. We found that 21 out of 23 neonates (22 MMA, and 1PA) diagnosed through the Tuscany region NBS program exhibited significantly higher levels of C17 compared to controls. Twenty-three maternal deficiency (21 vitamin B12 deficiency, 1 homocystinuria and 1 gastrin deficiency) samples and 82 false positive for elevated propionylcarnitine (C3) were also analyzed. Conclusions We have characterized a novel biomarker able to detect propionate disorders during expanded newborn screening (NBS). The use of this new biomarker may improve the analytical performances of NBS programs especially in laboratories where second tier tests are not performed. [ABSTRACT FROM AUTHOR]

Carbamazepine (CBZ) is a first-line drug for the treatment of different forms of epilepsy and the first choice drug for trigeminal neuralgia. CBZ is metabolized in the liver by oxidation into carbamazepine-10,11-epoxide (CBZE), its major metabolite which is equipotent and known to contribute to the pharmacological activity of CBZ. The aim of the present study was to develop and validate a reliable, selective and sensitive liquid chromatography–tandem mass spectrometry method for the simultaneous quantification of CBZ and its active metabolite in dried blood spots (DBS). The extraction process was carried out from DBS using methanol–water–formic acid (80:20:0.1, v/v/v). Chromatographic elution was achieved by using a linear gradient with a mobile phase consisting of acetonitrile–water–0.1% formic acid at a flow rate of 0.50 mL/min. The method was linear over the range 1–40 mg/L and 0.25–20 mg/L for CBZ and CBZE, respectively. The limit of quantification was 0.75 mg/L and 0.25 mg/L for CBZ and CBZE. Intra-day and inter-day assay precisions were found to be lower than 5.13%, 6.46% and 11.76%, 4.72% with mean percentage accuracies of 102.1%, 97.5% and 99.2%, 97.8% for CBZ and CBZE. We successfully applied the method for determining DBS finger-prick samples in paediatric patients and confirmed the results with concentrations measured in matched plasma samples. This novel approach allows quantification of CBZ and its metabolite from only one 3.2 mm DBS disc by LC–MS/MS thus combining advantages of DBS technique and LC–MS/MS in clinical practice. [ABSTRACT FROM AUTHOR]

Abstract: Propranolol, a non-selective beta blocker drug, is used in young infants and newborns for treating several heart diseases; its pharmacokinetics has been extensively evaluated in adult patients using extrapolation to treat pediatric population. The purpose of the present study was to develop and validate a method to measure propranolol levels in dried blood spots. The analysis was performed by using liquid chromatography/tandem mass spectrometry operating in multiple reaction monitoring mode. The calibration curve in matrix was linear in the concentration range of 2.5–200μg/L with correlation coefficient r =0.9996. Intra-day and inter-day precisions and biases were less than 8.0% (n =10) and 11.5% (n =10) respectively. The recoveries ranged from 94 to 100% and the matrix effect did not result in a severe signal suppression. Propranolol on dried blood spot showed a good stability at three different temperatures for one month. This paper describes a micromethod for measuring propranolol levels on dried blood spot, which determines a great advantage in neonates or young infants during pharmacokinetic studies because of less invasive sampling and small blood volume required. [Copyright &y& Elsevier]

Abstract: Linezolid is a new drug from the oxazolidinone class of antibiotics used against mycobacteria and multi-drug resistant (MDR) Gram-positive bacterial infections, which may are also glycopeptide-resistant. The drug usage in pediatric age needs an accurate drug monitoring for effective patient management. The aim of this study was to evaluate the use of dried blood spot (DBS) specimens to determinate linezolid levels during treatment. Advantages of DBS include short collection time, low invasiveness, ease and low cost of sample collection, transport and storage. The analysis was performed in LC–MS/MS operating in positive ion mode and multiple reaction monitoring (MRM) mode. The calibration curve in matrix was linear in the concentration range of 1–100mg/L with correlation coefficient value of 0.9987. Intraday and interday coefficients of variation were within 3.6% and 13.0%, respectively. We also tested the thermal and temporal drug stability in dried blood spots at four different temperatures to evaluate the risks of sample delivery in different conditions. The short term stability studies showed that linezolid concentration remained stable for at least one month under all the conditions tested. This new assay has favorable characteristics being highly precise and accurate and allows a fast linezolid analysis with a total run time 22min long, in gradient analysis. Concentration data for plasma and DBS samples from patients after treatment were compared showing a good correlation. Correlation between DBS data and serum samples measured by HPLC–UV was satisfactory. The benefit for patients is the ability to monitor the treatment with a simple and convenient sample collection at home. [Copyright &y& Elsevier]

Abstract: Ertapenem (Invanz®) is a newly developed carbapenem β-lactam antimicrobial agent. The drug usage in pediatric age needs an accurate drug monitoring for effective patient management. The aim of this study was to evaluate the use of dried blood spot (DBS) specimens to measure ertapenem concentration during treatment. The analysis was performed by UPLC–MS/MS operating in multiple reaction monitoring (MRM) mode. The calibration curve in matrix was linear in the concentration range of 0.5–100mg/L with correlation coefficient value higher than 0.997. Performance parameters of this method like lower limit of detection (LLOD, 0.2mg/L), lower limit of quantification (LLOQ, 0.5mg/L), matrix effect (20%), intra- and inter-day imprecision (CV within than 15%) and accuracy (between 94 and 155%) of drug concentrations have been evaluated. The drug stability at different temperatures was tested for one month, to evaluate the risks of sample delivery at different climatic conditions. The reported method allows now ertapenem analysis and offers many advantages for patients including the possibility of collecting samples at home. This new assay is both precise and accurate and is especially suitable for therapeutic drug monitoring and pharmacokinetic studies in neonates in whom obtaining larger blood samples is not convenient or possible. [Copyright &y& Elsevier]