Pharmacokinetic study on carbamazepine and gabapentin employing HemaXis DB, a novel device for convenient whole blood self-sampling, and the GERSTEL Dried Blood Spot Autosampler (DBS-A) coupled online to LC-MS/MS

Significance of the Topic

The accurate tracking of drug concentrations in blood over time is essential for pharmacokinetic profiling, dose optimization and therapeutic drug monitoring.
Innovations in dried blood spot (DBS) sampling and automated analysis reduce costs, simplify logistics and enable frequent self-sampling without medical personnel.

Objectives and Study Overview

This study evaluated a fully automated workflow combining HemaXis DB volumetric DBS collection and the GERSTEL Dried Blood Spot Autosampler (DBS-A) online with LC-MS/MS for carbamazepine, its active metabolite carbamazepine-10,11-epoxide, and gabapentin.
Single oral doses (200 mg carbamazepine retard, 300 mg gabapentin) were administered to a healthy volunteer, and capillary blood samples were self-collected at multiple time points.
Concentration-time profiles were generated and benchmarked against literature data to demonstrate method feasibility for pharmacokinetic studies.

Methodology and Instrumentation

• Sampling: HemaXis DB devices enabled accurate 5 µL (DB5) or 10 µL (DB10) whole blood collection via a microfluidic chip and protected polymer envelope.
• Automation: The GERSTEL DBS-A, featuring a MultiPurpose Sampler (MPS) and online SPExos SPE cleanup, handled DBS card insertion, solvent desorption and transfer to LC-MS/MS without manual intervention.
• Chromatography: Agilent Poroshell 120 EC-C18 column (3 × 50 mm, 2.7 µm) with gradient elution (mobile phases: ammonium formate buffer and acetonitrile), flow 0.5 mL/min at 30 °C.
• Mass Spectrometry: Agilent 6460 triple quadrupole operated in positive MRM mode; customized transitions for each analyte and deuterated internal standards.
• Method Performance: Calibration ranges 10–4000 ng/mL (quadratic or linear), LOQs 2–8 ng/mL, precision (RSD) 3–11%, no carry-over observed.

Main Results and Discussion

• Calibration and Sensitivity: Full-spot online desorption achieved single-digit ng/mL LOQs from only 5 µL blood; correlation coefficients R² > 0.99 across analytes.
• Precision and Accuracy: Repeat analyses (n=8) at low and high concentrations gave RSDs ≤ 7%, with sampling precision (duplicate or five-fold DBS) between 3.1% and 11.0%.
• Pharmacokinetic Profiles: Carbamazepine Cmax ~1800 ng/mL (13–33 h post-dose), metabolite Cmax ~80 ng/mL (33–48 h), gabapentin Cmax ~4500 ng/mL (2.5 h), in agreement with published plasma data.
• Operational Throughput: Automated sample-to-result workflow with 14 min runtime per carbamazepine assay and 18 min for gabapentin allows processing of 80–100 samples/day.

Benefits and Practical Application

• Cost Reduction: Eliminates refrigerated transport and centrifugation, lowering logistics and handling expenses.
• Self-Sampling: Patients can perform finger-prick DBS collection at home, enabling flexible sampling schedules and improved patient compliance.
• Data Quality: Full-spot analysis and internal standardization deliver robust quantitative results, suitable for clinical, QA/QC and anti-doping studies.
• Safety and Convenience: Polymer envelope secures biohazard containment; dried format simplifies storage and shipment.

Future Trends and Opportunities for Use

• Plasma-DST: Development of HemaXis DX devices for volumetric plasma sampling may further align DBS with conventional plasma-based pharmacokinetics.
• Expanded Analyte Panels: The automated DBS-A workflow can adapt to emerging biomarkers, therapeutic drugs and metabolites across clinical and forensic fields.
• High-Throughput Screening: Integration with 1000 bar SPE systems and multiplexed sampling racks promises further reductions in cycle time.
• Decentralized Trials: Remote patient monitoring and telemedicine benefits by enabling frequent sampling without clinic visits.

Conclusion

The integration of HemaXis DB self-sampling with the GERSTEL DBS-A online to LC-MS/MS offers a reliable, sensitive and high-throughput solution for pharmacokinetic studies.
The methods deliver single-digit ng/mL quantification from minimal blood volumes, allow patient-driven sampling, and reduce logistical burdens compared to venous blood assays.
Adoption of this automated workflow can streamline drug development, therapeutic monitoring and compliance testing across diverse applications.

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