Volumetric Absorptive Microsampling: A New Sampling Tool for Therapeutic Drug Monitoring of Antiepileptic Drugs.

BACKGROUND: Volumetric absorptive microsampling (VAMS) is a novel sampling technique for the collection of fixed-volume capillary blood. In this study, a new analytical method was developed and used to quantify 14 different antiepileptic drugs (AEDs) and 2 active metabolites in samples collected by VAMS. These data were compared with concentration measurements in plasma. METHODS: The authors developed a selective and sensitive liquid chromatography-mass spectrometry (LC-MS/MS) assay to measure the concentrations of several AEDs in whole blood collected by VAMS, which were compared with a commercially available LC-MS/MS kit for AED monitoring in plasma. Drugs and internal standards were extracted from whole blood/plasma samples by a simple protein precipitation. RESULTS: An LC-MS/MS method analyzing VAMS samples was successfully developed and validated for the determination of various AED concentrations in whole blood according to EMA guidelines for bioanalytical method validation. Extraction recovery was between 91% and 110%. No matrix effect was found. The method was linear for all drugs with R ≥0.989 in all cases. Intra-assay and inter-assay reproducibility analyses demonstrated accuracy and precision within acceptance criteria. Carry over and interferences were negligible. No volumetric HCT% bias was found at 3 different HCT values (35%-55%) with recovery being consistently above 87%. Samples are very stable at temperatures ranging from -20°C to 37°C and for a 4-month period. Leftover EDTA samples from 133 patients were tested to determine concentration differences between plasma and whole blood sampled by VAMS. The resulting difference varied less than 15% apart from those drugs with a blood/plasma ratio (R) different from 1. CONCLUSIONS: The assay allows for highly sensitive and selective quantification of several AEDs in whole blood samples collected by VAMS. The developed method is accurate and precise and free from matrix effects and volumetric HCT% bias.

LC-MS/MS-Based Quantification of 9 Antiepileptic Drugs From a Dried Sample Spot Device.

BACKGROUND: Therapeutic drug monitoring (TDM) of antiepileptic drugs (AEDs) is commonly performed on plasma or serum. The use of dried plasma spots (DPSs) could represent a useful tool to facilitate sample shipment to reference laboratories. In this article, the authors describe the application of a commercially available UHPLC-MS/MS method for the determination of 9 commonly prescribed AEDs (levetiracetam, lacosamide, topiramate, ethosuximide, lamotrigine, rufinamide, zonisamide, primidone, and oxcarbazepine and its active metabolite 10-OH-monohydroxycarbazepine) to DPS collected on dried sample spot devices (DSSDs). METHOD: Fifty microliters of plasma were spotted on DSSD. After being air-dried at room temperature, they were extracted using an organic extraction solution containing the appropriate deuterated internal standards. The chromatographic separation was performed on a UHPLC reversed-phase C-18 column, and the analytes were quantified using a triple quadrupole mass spectrometer (LC-MS/MS). RESULTS: The assay was linear over the concentration ranges tested with a total runtime of 10.3 minutes. Recovery ranged from 93.7% to 106.8%. Intraday and interday precision for all quality control levels, including lower limit of quantification, ranged from 2.1% to 18.4% and 2.1% to 13.2%. Intraday and interday accuracy biases ranged from -11.7% to 14.3% and -9.2% to 8.0%. The absence of matrix effects was also tested and confirmed. Real samples derived from patients under therapy were also analyzed, and the comparison of results obtained from DSSD with those obtained from plasma showed that the 2 matrices were interchangeable. Stability tests performed on both quality controls, and real samples demonstrated that DSSDs can be easily stored and shipped at room temperature for 15 days. CONCLUSIONS: The application of the LC-MS/MS method allowed the authors to obtain a very specific, sensitive, and rapid (total runtime = 10.3 minutes) quantification of 9 AEDs starting from very low volumes of plasma samples. The main advantage of DPS over wet samples is room temperature storage and shipment, which lowers shipment costs and makes it suitable for routine TDM. Moreover, in comparison with other alternative matrices, DPS allows for the use of the same therapeutic ranges on which routine TDM is based. DPS on DSSD can thus be considered as a useful and cheap tool for the broader application of TDM.

A Liquid Chromatography-Mass Spectrometry Assay for Determination of Perampanel and Concomitant Antiepileptic Drugs in the Plasma of Patients With Epilepsy Compared With a Fluorescent HPLC Assay.

BACKGROUND: Perampanel is a novel noncompetitive selective antagonist at the postsynaptic ionotropic alpha-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid (AMPA) glutamate receptor, which is approved as an adjunctive agent for the treatment of partial-onset seizure with or without secondary generalization and for primary generalized tonic-clonic seizure in patients with epilepsy who are at least 12 years of age. Limited information is available about the clinical utility of therapeutic drug monitoring of perampanel and therapeutic ranges are so far not established. Therefore, perampanel titration should be performed especially in case of insufficient success of the drug. METHODS: The authors developed a selective and sensitive LC-MS/MS (liquid chromatography-mass spectrometry) assay to monitor perampanel concentrations in plasma, which was compared to a commercially available high-performance liquid chromatography kit with fluorescent detection. Perampanel and the internal standard were extracted from plasma samples by a simple protein precipitation. The method allows the simultaneous quantification of perampanel and several other antiepileptic drugs (AEDs). RESULTS: Data were evaluated according to EMA guidelines for bioanalytical method validation. Extraction recovery of perampanel from human plasma was consistently above 98%. No matrix effect was found. Analytical interferences by other AEDs were not observed. The method was linear in the range from 2.5 to 2800 ng/mL. Intra-assay and interassay reproducibility analyses demonstrated accuracy and precision within acceptance criteria. Data collected from 95 patients, given perampanel as their maintenance antiepileptic therapy, showed a very strong correlation between the 2 methods. CONCLUSIONS: The assay allows for highly sensitive and selective quantification of perampanel and concomitant AEDs in patient plasma samples and can be easily implemented in clinical settings. Our findings are in agreement with previously published data in patients comedicated with enzyme inducer AEDs, but seem to indicate a possible interaction in patients treated with the enzyme inhibitor drug valproic acid.

Evaluation of a Novel Immunoassay for Lacosamide Therapeutic Drug Monitoring: Comparison With a Liquid Chromatography-Mass Spectrometry Assay.

BACKGROUND: Monitoring serum levels of lacosamide, other than to establish individualized reference ranges may be helpful in several settings, including patients with liver and/or kidney failure or settings that may result in altered pharmacokinetic characteristics and to assess patients' compliance with therapy. In this study, the EurekaOne liquid chromatography-mass spectrometry (LC-MS/MS) method (in use method) and the ARK immunoassay method (new method) for lacosamide monitoring were compared. METHODS: Lacosamide concentrations were determined in 39 patient samples using (1) antiepileptic drug LC-MS/MS kit by EurekaOne on a Thermo Fisher Scientific TSQuantum Access Max system and (2) the lacosamide immunoassay by ARK Diagnostic Inc. (research use only kit), on a Abbott Architect System. RESULTS: Measured total imprecision of the new method is 6.29% at 6.59 µmol/L, 8.82% at 30.20 µmol/L, and 6.45% at 64.51 µmol/L. Passing-Bablok regression analysis showed a nonsignificant intercept of -0.03015 [95% confidence interval (CI), -1.2243 to 0.8593] and a slope of 1.05 (95% CI, 0.9973-1.1166), showing that the method does not deviate from linearity and absence of proportional systematic error. Bland-Altman analysis showed a systematic bias of -3.296% (95% CI, -5.81 to -0.78) with 95% of the LC-MS/MS-ARK mean % of differences ranging from -18.5 to 11.9. Despite this bias, data of the combined imprecision of the 2 methods show that the new method is still acceptable within the maximum allowable error of 15%. CONCLUSIONS: The performance of the new ARK method on the Architect system is acceptable and may be used routinely to measure serum lacosamide concentration in the clinic although the nature of the bias has to be carefully addressed.