Determination of plasma topiramate concentration using LC-MS/MS for pharmacokinetic and bioequivalence studies in healthy Korean volunteers

Pharmacokinetics and bioequivalence evaluation of two oral formulations of topiramate tablets in healthy Chinese male volunteers under fasting and fed conditions

Topiramate is an antiepileptic drug (AED) that is effective in treating various types of epilepsy. This study evaluated the bioequivalence and safety of two topiramate tablets in healthy Chinese subjects under fasting and fed conditions. We designed an open-label, randomized, single-dose, two-period, crossover trial protocol. Two independent trials were conducted, each including 26 volunteers. In the fed trial, subjects were randomly assigned to two groups (1:1 ratio) to receive either 100 mg of test formulation or reference formulation of topiramate. After a 21-day washout period, crossover administration was implemented. The fasting trial design was similar to that of the fed trial. Plasma concentrations of topiramate were determined using a validated method (high-performance liquid chromatography-tandem mass spectrometry, HPLC-MS/MS). Pharmacokinetic (PK) parameters such as maximum plasma drug concentration (Cmax), time to reach maximum concentration (Tmax), and the area under the plasma concentration-time curve from time 0 to 72 h (AUC0-72) were calculated using a non-compartment model to evaluate the bioequivalence of two formulations. The safety of volunteers was monitored during the entire study. In the fasting trial, 90% confidence intervals (CIs) of geometric mean ratios (GMRs) of the test to reference formulations were 101.26-112.94% for Cmax and 98.50-102.69% for AUC0-72, all within the recognized bioequivalence range of 80.00-125.00%. In the fed trial, 90% CIs of GMRs of the test to reference formulations were 92.08-101.54% for Cmax and 95.81-99.79% for AUC0-72, both were within the bioequivalence range of 80.00-125.00%. Research findings indicated that the two topiramate formulations were bioequivalent and had a favorable safety profile.

A Greener Stability-Indicating High-Performance Thin-Layer Chromatography Approach for the Estimation of Topiramate

Despite various reported analytical methods for topiramate (TPM) analysis, greener analytical approaches are scarce in literature. As a consequence, the objective of the current research is to design a normal-phase stability-indicating high-performance thin-layer chromatography (SI-HPTLC) methodology for TPM analysis in marketed tablet dosage forms that is rapid, sensitive, and greener. TPM was derivatized densitometrically and analyzed at 423 nm in visible mode with anisaldehyde-sulfuric acid as the derivatizing agent. The greener SI-HPTLC technique was linear in the 30-1200 ng band-1 range. In addition, the suggested SI-HPTLC methodology for TPM analysis was simple, rapid, cheaper, precise, robust, sensitive, and environmentally friendly. The greener SI-HPTLC method was able to detect TPM along with its degradation products under acid, base, and oxidative degradation conditions. However, no TPM degradation was recorded under thermal and photolytic stress conditions. TPM contents in commercial tablet dosage forms were recorded as 99.14%. Using 12 different principles of green analytical chemistry, the overall analytical GREEnness (AGREE) score for the greener SI-HPTLC method was calculated to be 0.76, confirming the proposed normal-phase SI-HPTLC method's good greener nature. Overall, these results demonstrated that the suggested SI-HPTLC technique for TPM measurement in pharmaceutical products was reliable and selective.

Topiramate-chitosan nanoparticles prevent morphine reinstatement with no memory impairment: Dopaminergic and glutamatergic molecular aspects in rats

Besides their clinical application, chronic misuse of opioids has often been associated to drug addiction due to their addictive properties, underlying neuroadaptations of AMPA glutamate-receptor-dependent synaptic plasticity. Topiramate (TPM), an AMPAR antagonist, has been used to treat psychostimulants addiction, despite its harmful effects on memory. This study aimed to evaluate the effects of a novel topiramate nanosystem on molecular changes related to morphine reinstatement. Rats were previously exposed to morphine in conditioned place preference (CPP) paradigm and treated with topiramate-chitosan nanoparticles (TPM-CS-NP) or non-encapsulated topiramate in solution (S-TPM) during CPP extinction; following memory performance evaluation, they were re-exposed to morphine reinstatement. While morphine-CPP extinction was comparable among all experimental groups, TPM-CS-NP treatment prevented morphine reinstatement, preserving memory performance, which was impaired by both morphine-conditioning and S-TPM treatment. In the NAc, morphine increased D1R, D2R, D3R, DAT, GluA1 and MOR immunoreactivity. It also increased D1R, DAT, GluA1 and MOR in the dorsal hippocampus. TPM-CS-NP treatment decreased D1R, D3R and GluA1 and increased DAT in the NAc, decreasing GluA1 and increasing D2 and DAT in the dorsal hippocampus. Taken together, we may infer that TPM-CS-NP treatment was able to prevent the morphine reinstatement without memory impairment. Therefore, TPM-CS-NP may be considered an innovative therapeutic tool due to its property to prevent opioid reinstatement because it acts modifying both dopaminergic and glutamatergic neurotransmission, which are commonly related to morphine addiction.

High performance liquid chromatography: A versatile tool for assaying antiepileptic drugs in biological matrices

Epilepsy is a recurrent long-term illness occurring in approximately 1.0% of the world's population. There are currently about 29 approved antiepileptic drugs for the management of epilepsy. Due to narrow therapeutic indices of most antiepileptic drugs, clinical pharmacokinetic characteristics and therapeutic drug monitoring of these drugs are imperative. The objectives of this review were to identify common chromatographic principles, requirements and/or conditions for high-performance liquid chromatography as applied to assay of antiepileptic drugs in biological matrices. The review was conducted using 66 peer reviewed articles (1990 to 2020) from 29 journals that were sought via PubMed, Science Direct and Google Scholar. In all, 29 antiepileptic drugs were assayed from 6 different biological matrices. Forty-three of the reviewed articles estimated the concentration of only one antiepileptic drug, whilst 23 articles focused on simultaneous determination of two or more antiepileptic drugs. Thirty-four, 20, and 14 articles reported using liquid-liquid extraction, protein precipitation, or solid phase extraction for sample clean up, respectively. The ratio of reversed-phase to normal phase, LC-UV to LC-MS and isocratic elution to gradient elution were 61:3, 43:7 and 55:11, respectively. With the exception of one article the reported recoveries ranged from 60.3% to 109.6%. It is noteworthy, that, the performance metrics of high-performance liquid chromatography are better compared to other assays of antiepileptic drugs in biological matrices. This review describes the relevant liquid chromatographic method conditions over the past 30 years for the analysis of this class of drugs, which provides a basis for further method development and optimization.

A novel LC-MS/MS method for the simultaneous quantification of topiramate and its main metabolites in human plasma

The aim of the present report was to develop and validate simple, sensitive and reliable LC-MS/MS method for quantification of topiramate (TPM) and its main metabolites: 2,3-desisopropylidene TPM, 4,5-desisopropylidene TPM, 10-OH TPM and 9-OH TPM in human plasma samples. The most abundant metabolite 2,3-desisopropylidene TPM was isolated from patients urine, characterized and afterwards used as an authentic standard for method development and validation. Sample preparation method employs 100μL of plasma sample and liquid-liquid extraction with a mixture of ethyl acetate and diethyl ether as extraction solvent. Chromatographic separation was achieved on a 1290 Infinity UHPLC coupled to 6460 Triple Quad Mass Spectrometer operated in negative MRM mode using Kinetex C18 column (50×2.1mm, 2.6μm) by gradient elution using water and methanol as a mobile phase and stable isotope labeled TPM as internal standard. The method showed to be selective, accurate, precise and linear over the concentration ranges of 0.10-20μg/mL for TPM, 0.01-2.0μg/mL for 2,3-desisopropylidene TPM, and 0.001-0.200μg/mL for 4,5-desisopropylidene TPM, 10-OH TPM and 9-OH TPM. The described method is the first fully validated method capable of simultaneous determination of TPM and its main metabolites in plasma over the selected analytical range. The suitability of the method was successfully demonstrated by the quantification of all analytes in plasma samples of patients with epilepsy and can be considered as reliable analytical tool for future investigations of the TPM metabolism.

Development and validation of dried blood spots technique for quantitative determination of topiramate using liquid chromatography-tandem mass spectrometry

An LC-MS/MS method for determination of the anti-epileptic drug topiramate (TPM) in dried blood spot (DBS) samples was developed and validated. DBS samples were prepared by spotting 30 μL of spiked whole blood onto FTA(TM) DMPK-C cards and drying for at least 3 h. Six-millimetre punched spots were then extracted by using a mixture of methanol and water (90:10, v/v) with deuterated internal standard (topiramate-d12). The extracted samples were injected into a liquid chromatograph equipped with a tandem mass spectrometric detector. Negative ions were monitored in the selected reaction monitoring mode and transitions m/z 338.2 → 78.1 and m/z 350.3 → 78.1 were used for the quantitative evaluation of TPM and internal standard, respectively. The results obtained from validation were statistically evaluated according to the requirements of the European Medicines Agency and US Food and Drug Administration regulatory guidelines. The linearity of the method was checked within a concentration range from 10 to 2000 ng/mL. The validation results indicate that the method is accurate, precise, sensitive, selective and reproducible.

Modern methods for analysis of antiepileptic drugs in the biological fluids for pharmacokinetics, bioequivalence and therapeutic drug monitoring

Epilepsy is a chronic disease occurring in approximately 1.0% of the world's population. About 30% of the epileptic patients treated with availably antiepileptic drugs (AEDs) continue to have seizures and are considered therapy-resistant or refractory patients. The ultimate goal for the use of AEDs is complete cessation of seizures without side effects. Because of a narrow therapeutic index of AEDs, a complete understanding of its clinical pharmacokinetics is essential for understanding of the pharmacodynamics of these drugs. These drug concentrations in biological fluids serve as surrogate markers and can be used to guide or target drug dosing. Because early studies demonstrated clinical and/or electroencephalographic correlations with serum concentrations of several AEDs, It has been almost 50 years since clinicians started using plasma concentrations of AEDs to optimize pharmacotherapy in patients with epilepsy. Therefore, validated analytical method for concentrations of AEDs in biological fluids is a necessity in order to explore pharmacokinetics, bioequivalence and TDM in various clinical situations. There are hundreds of published articles on the analysis of specific AEDs by a wide variety of analytical methods in biological samples have appears over the past decade. This review intends to provide an updated, concise overview on the modern method development for monitoring AEDs for pharmacokinetic studies, bioequivalence and therapeutic drug monitoring.

A simple, rapid and specific method for measurement of topiramate in human plasma by LC-MS/MS employing automated solid-phase extraction techniques: Application for bioequivalence study

A rapid liquid chromatography coupled with ESI tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantification of topiramate in heparinized human plasma. The plasma samples were prepared by solid-phase extraction (SPE) method without drying and then reconstitution. Topiramate and the topiramate d-12 internal standard (IS) were chromatographed on a Betasil C18 column at a flow rate of 0.5 mL/min. The total run time was 1.80 min. An ESI interface with negative ion mode was selected for ionization of analyte and IS. The mass transition [M-H] ions used for detection were m/z 338.10→78.20 for topiramate, m/z 350.40→90.10 for IS. The method was linear in the concentration range of 10-4200 ng/mL with r≥0.9992. Recovery of topiramate and IS ranged from 78.20 to 87.74%. The validated method has been successfully used to analyze human plasma samples for application in 100 mg fasted and fed pharmacokinetic studies.