Background: Lamotrigine (LTG), topiramate (TPM), and oxcarbazepine (OXC) are
commonly used antiepileptic drugs. The bioactivity and toxicity of these drugs were related to their
blood concentrations which varied greatly among individuals and required to be monitored for dose
adjustment. However, the commercial method for monitoring of these drugs is not available in China.
Methods: A UHPLC-MS/MS method for simultaneous determination of LTG, TPM, OXC, and OXC
active metabolite (10,11-dihydro-10-hydroxycarbazepine, MHD) was developed and validated according
to the guidelines and applied in clinical practice.
Results: The separation was achieved by using methanol and water (both contain 0.1% formic acid)
at 0.4 mL/min under gradient elution within 3 min. For all analytes, the isotope internal standard was
used; the selectivity was good without significant carry over; LTG and TPM were linear between
0.06 to 12 mg/L while OXC and MHD were linear between 0.03 to 6 mg/L, the upper limit could be
10-fold higher because 10-fold dilution with water did not affect the results; the intra-day and interday
bias and imprecision were -13.11% to 5.42% and < 13.32%; the internal standard normalized recovery
and matrix factor were 90.95% to 111.94% and 95.57% to 109.91%; and all analytes were
stable under tested conditions. LTG and OXC-D4 shared two ion pairs m/z 257.1 > 212.0 and 257.1 >
184.0, and m/z 257.1 > 240.0 was suggested for OXC-D4 quantitation. Lamotrigine and lamotrigine-
13C3 shared three ion pairs m/z 259.0 > 214.0, 259.0 > 168.0 and 259.0 > 159.0, and m/z 259.0 >
144.9 was suggested for LTG-13C3 quantitation. CBZ had a slight influence on OXC analysis only at
0.225 mg/L (bias, 20.24%) but did not affect MHD analysis. Optimization of chromatography conditions
was useful to avoid the influence of isobaric mass transitions on analysis. This method has been
successfully applied in 208 patients with epilepsy for dose adjustment.
Conclusion: An accurate, robust, rapid, and simple method for simultaneous determination of LTG,
TPM, OXC, and MHD by UHPLC-MS/MS was developed, validated, and successfully applied in patients
with epilepsy for dose adjustment. The experiences during method development, validation,
and application might be helpful for other researchers.