Therapeutic Drug Monitoring of Lamotrigine, Lacosamide, and Levetiracetam in Dried Capillary Blood-Determination of Conversion Factors for Serum-Based Reference Ranges

Non-invasive therapeutic drug monitoring: LC-MS validation for lamotrigine quantification in dried blood spot and oral fluid/saliva

Epilepsy, affecting over 50 million people globally, presents a significant neurological challenge. Effective prevention of epileptic seizures relies on proper administration and monitoring of Anti-Seizure Medication (ASMs). Therapeutic Drug Monitoring (TDM) ensures optimal dosage adjustment, minimizing adverse effects and potential drug interactions. While traditional venous blood collection for TDM may be stressful, emerging alternative sampling methods, particularly Dried Blood Spot (DBS) or oral fluid offer less invasive way of sampling. This study aimed to develop and validate an analytical method for the determination of lamotrigine in such alternative samples. The sample, either DBS or oral fluid, was subjected to extraction, evaporation, and reconstitution in 15 % acetonitrile containing 0.1 % formic acid. A Kinetex C18 Polar column was used for liquid chromatographic separation and MS in ESI+ mode was used for detection and quantitation of lamotrigine using an isotopically labelled internal standard according to EMA guidelines. The calibration range of the developed method enables the determination of lamotrigine in the concentration range of 1-30 μg/mL in DBS and 0.5-20 μg/mL in oral fluid. Oral fluid and DBS samples from patients treated with lamotrigine analysed by the developed method were compared to plasma concentrations measured by the hospital's accredited laboratory. Preliminary results indicate a promising potential for these alternative matrices in clinical TDM applications. By offering a less invasive sampling approach, this method improves the accessibility and safety of pharmacotherapy for epilepsy patients. The results of this study lay the foundation for further clinical applications by implementing alternative matrix TDM, which may significantly advance personalized care in epilepsy management.

Therapeutic drug monitoring of levetiracetam - Is dried blood spot sampling suitable?

BACKGROUND

Therapeutic drug monitoring helps prevent seizures and minimize side effects in epilepsy patients. Phlebotomy is the gold standard for blood collection but can be difficult for children, pregnant women, and patients in remote areas. We previously validated dried blood spot (DBS) sampling for carbamazepine, lamotrigine, levetiracetam (LEV), and valproic acid. Uncertainties in LEV comparisons from the previous validation were further investigated in this study by increasing sample numbers and comparing results using both immunochemistry and LC-MS/MS methods. Additionally, capillary and venous DBS were compared, and the stability of samples during mail transport was assessed.

AIM

To compare LEV concentrations in capillary DBS and plasma, and to assess the stability of capillary DBS during transportation.

METHOD

Capillary and venous blood samples were collected from 40 LEV-treated patients. Concentrations were measured using immunochemistry and liquid chromatography tandem mass spectrometry methods. Comparisons between matrices and methods were analyzed with Passing-Bablok regression and Bland-Altman plots.

RESULTS

No proportional bias was found in regression analysis and Bland-Altman plots showed no bias between methods. For capillary DBS versus plasma concentrations, 92.1 % of values were within 20 % of the mean. No bias was detected between capillary and venous DBS, with deviations within acceptable limits. Sample stability was maintained during mail transport.

CONCLUSION

The concentrations obtained for LEV in capillary DBS versus plasma showed that therapeutic drug monitoring of LEV can be performed as at-home self-sampling with DBS mailed to the laboratory for analysis.

An LC-MS/MS Method for Quantification of Lamotrigine and Its Main Metabolite in Dried Blood Spots

BACKGROUND

The antiepileptic drug lamotrigine (LTG) shows high pharmacokinetic variability due to genotype influence and concomitant use of glucuronidation inducers and inhibitors, both of which may be frequently taken by elderly patients. Our goal was to develop a reliable quantification method for lamotrigine and its main glucuronide metabolite lamotrigine-N2-glucuronide (LTG-N2-GLU) in dried blood spots (DBS) to enable routine therapeutic drug monitoring and to identify altered metabolic activity for early detection of drug interactions possibly leading to suboptimal drug response.

RESULTS

The analytical method was validated in terms of selectivity, accuracy, precision, matrix effects, haematocrit, blood spot volume influence, and stability. It was applied to a clinical study, and the DBS results were compared to the concentrations determined in plasma samples. A good correlation was established for both analytes in DBS and plasma samples, taking into account the haematocrit and blood cell-to-plasma partition coefficients. It was demonstrated that the method is suitable for the determination of the metabolite-to-parent ratio to reveal the metabolic status of individual patients.

CONCLUSIONS

The clinical validation performed confirmed that the DBS technique is a reliable alternative for plasma lamotrigine and its glucuronide determination.

Titania-based fabric phase sorptive extraction approach for the determination of antiepileptic drugs, levetiracetam and lamotrigine in urine samples using high-performance liquid chromatography-photo diode array detection

A new fabric phase sorptive extraction (FPSE) based separation and enrichment method was developed for sensitive determination of two antiepileptic drug molecules, Levetiracetam (LEV) and Lamotrigine (LTG). The analysis of these drug molecules was performed with high-performance liquid chromatography equipped with photodiode array detector (HPLC-PDA) after FPSE. HPLC analysis was carried out by using phenyl hexyl column, under isocratic conditions with the mobile phase composed of pH 3.0 buffer-acetonitrile (77:23 v: v). All parameters affecting the separation and enrichment process were studied and optimized step by step. The linear working range of the developed method was calculated in the range of 10.0-1000.0 ng mL-1 for both the drug molecules (LEV and LTG). The limits of detection of the method (LODs) were calculated as 2.72 and 3.64 ng mL-1, respectively. The relative standard deviation (%RSD) values of the developed method as an indicator of precision were varied between 4.0 and 7.3. The accuracy of the optimized FPSE method was determined by the recovery tests utilizing spiked samples and results were assessed in the range from 94.6 to 106.3%. This is the first application of sol-gel Titania polycaprolactone-polydimethylsiloxane-polycaprolactone (Ti-PCAP-PDMS-PCAP) based FPSE membrane in the determination of antiepileptic drug molecules.