A validated chiral LC method for the enantioselective analysis of Levetiracetam and its enantiomer R-α-ethyl-2-oxo-pyrrolidine acetamide on amylose-based stationary phase

Determination of levetiracetam by GC-MS and effects of storage conditions and gastric digestive systems on drug samples

Background: Epilepsy is a neurologic condition that is occurs globally and is associated with various degrees of seizures. Levetiracetam is an approved drug that is commonly used to treat seizures in juvenile epileptic patients. Accurate quantification of the drug's active compound and determining its stability in the stomach after oral administration are important tasks that must be performed. Results & methodology: Levetiracetam was extracted from drug samples and quantified by gas chromatography mass spectrometry using calibration standards. Stability of levetiracetam was studied under various storage conditions and in simulated gastric conditions. The calibration plot determined for levetiracetam showed good linearity with a coefficient of determination value of 0.9991. The limits of detection and quantification were found to be 0.004 and 0.014 μg·ml^-1, respectively. The structural integrity of levetiracetam did not change within a 4-h period under the simulated gastric conditions, and no significant degradation was observed for the different storage temperatures tested. Discussion & conclusion: An accurate and sensitive quantitative method was developed for the determination of levetiracetam in drug samples. The stability of the drug active compound was monitored under various storage and gastric conditions. The levetiracetam content determined in the drug samples were within ±10% of the value stated on the drug labels.

Levetiracetam

A comprehensive profile of levetiracetam is presented in this chapter which includes its description, formula, elemental analysis, appearance, uses and applications. Different earlier studies included for example methods of synthesis are described with its typical structural schemes. The profile also listed the drug's physical characteristics indicating its solubility, X-ray powder diffraction pattern, thermal methods of analysis as well as its spectroscopic characteristics. Different methods of analysis which includes compendial method of analysis, as well as reported method of analysis which include spectrophotometry, spectrofluorometry, electrochemical method, chromatographic method, and immunoassay method of analysis. The study was include drug stability, clinical pharmacology, e.g., mechanism of action, pharmacokinetic study. Around 70 references are recorded as a proof of this chapter.

Stir bar-sorptive extraction, solid phase extraction and liquid-liquid extraction for levetiracetam determination in human plasma: comparing recovery rates

<p>Levetiracetam (LEV), an antiepileptic drug (AED) with favorable pharmacokinetic profile, is increasingly being used in clinical practice, although information on its metabolism and disposition are still being generated. Therefore a simple, robust and fast liquid-liquid extraction (LLE) followed by high-performance liquid chromatography method is described that could be used for both pharmacokinetic and therapeutic drug monitoring (TDM) purposes. Moreover, recovery rates of LEV in plasma were compared among LLE, stir bar-sorptive extraction (SBSE), and solid-phase extraction (SPE). Solvent extraction with dichloromethane yielded a plasma residue free from usual interferences such as commonly co-prescribed AEDs, and recoveries around 90% (LLE), 60% (SPE) and 10% (SBSE). Separation was obtained using reverse phase Select B column with ultraviolet detection (235 nm). Mobile phase consisted of methanol:sodium acetate buffer 0.125 M pH 4.4 (20:80, v/v). The method was linear over a range of 2.8-220.0 µg mL^-1. The intra- and inter-assay precision and accuracy were studied at three concentrations; relative standard deviation was less than 10%. The limit of quantification was 2.8 µg mL^-1. This robust method was successfully applied to analyze plasma samples from patients with epilepsy and therefore might be used for pharmacokinetic and TDM purposes.</p>

Chiral chromatographic resolution of antiepileptic drugs and their metabolites: a challenge from the optimization to the application

A large number of the antiepileptic drugs (AEDs) presently available for clinical practice are chiral compounds while others, although achiral, may originate pharmacologically active chiral metabolites in vivo. The well-known implications of chirality in pharmacokinetics and pharmacodynamics demand the investigation of pharmacological properties for a racemic mixture and each enantiomer. To achieve these objectives, appropriate chiral analytical methods must be available. This article provides the first review of the current state of the art in chiral chromatographic methods available for quantifying enantiomers of AEDs in distinct matrices. Particular attention is paid to the methodological aspects and optimization strategies that successfully allow enantiomeric chromatographic separation of chiral AEDs and/or metabolites. Furthermore, the relevance of these methods in supporting the discovery and development of chiral AEDs is emphasized. In parallel and whenever available, the principal validation parameters are herein considered and related to the stage of drug discovery and development. In an attempt to optimize anticonvulsant activity and simultaneously diminish toxic effects, many pharmaceutical companies have started to manufacture single enantiomers. Therefore, chiral chromatographic techniques will be essential and the information herein compiled can be used as a framework for developing them.

Optimized and validated flow-injection spectrophotometric analysis of topiramate, piracetam and levetiracetam in pharmaceutical formulations

Application of a sensitive and rapid flow injection analysis (FIA) method for determination of topiramate, piracetam, and levetiracetam in pharmaceutical formulations has been investigated. The method is based on the reaction with ortho-phtalaldehyde and 2-mercaptoethanol in a basic buffer and measurement of absorbance at 295 nm under flow conditions. Variables affecting the determination such as sample injection volume, pH, ionic strength, reagent concentrations, flow rate of reagent and other FIA parameters were optimized to produce the most sensitive and reproducible results using a quarter-fraction factorial design, for five factors at two levels. Also, the method has been optimized and fully validated in terms of linearity and range, limit of detection and quantitation, precision, selectivity and accuracy. The method was successfully applied to the analysis of pharmaceutical preparations.

Drug monitoring: simultaneous analysis of lamotrigine, oxcarbazepine, 10-hydroxycarbazepine, and zonisamide by HPLC-UV and a rapid GC method using a nitrogen-phosphorus detector for levetiracetam

A high-performance liquid chromatography (HPLC) assay using UV detection is described for the simultaneous measurement of the newer generation anti-epileptic medications lamotrigine, oxcarbazepine (parent drug and active metabolite 10- hydroxycarbazepine), and zonisamide. Detection of all four compounds can be done at 230 nm; however, there is a potential interference with zonisamide in patients on clonazepam therapy. Therefore, the method uses dual wavelength detection: 230 nm for oxcarbazepine and 10-hydroxycarbazepine and 270 nm for lamotrigine and zonisamide. In addition, a simple gas chromatography method using a nitrogen-phosphorus detector is described for the measurement of levetiracetam, another of the recently approved anti-epileptic medications. For both methods, limits of quantitation, linearities, accuracies, and imprecisions cover the therapeutic range for drug monitoring of patients. A wide variety of clinical drugs, including other anti-epileptic drugs, do not interfere with these assays. These procedures would be of special interest to clinical laboratories, particularly due to the limited availability of immunoassays for newer generation anti-epileptic medications and that therapeutic uses of these drugs are expanding beyond epilepsy to other neurologic and psychiatric disorders.

Enantiomeric impurity determination of levetiracetam using capillary electrochromatography

CEC was used to develop a method for the enantiomeric excess determination of levetiracetam, an antiepileptic drug. Different types of calibration curve were evaluated for use in the range between 0.01 and 1 mg/mL when aniracetam was used as an internal standard. The method gave comparable results when only the areas of the impurity were used in the calibration curve. The predicted detection and quantification limits from the S/N were 1.1 and 3.6 microg/mL, respectively. However, experimental results showed that LOD and LOQ were underestimated. Repeatability of injection was demonstrated by the RSD values obtained for retention time, resolution, ratios of the areas impurity/internal standard, and areas of impurity and internal standard individually, which were below or equal to 9.30%. The between-days variability experiments indicated that it is better to make a calibration curve daily. The finally selected calibration curves were used to test the accuracy of the developed method on bulk samples and Keppra tablets containing 250 mg levetiracetam. Both selected calibration curves performed similarly. The one using the internal standard information gave overall recoveries between 88 and 118%, while the one using areas gave results between 84 and 118%.

Determination of levetiracetam in human plasma/serum/saliva by liquid chromatography-electrospray tandem mass spectrometry

BACKGROUND

Levetiracetam (Keppra) is a novel antiepileptic drug recently approved by the U.S. Food and Drug Administration as an add-on therapy in the treatment of partial onset seizures in patients. We developed and describe a simple and rapid high performance liquid chromatography-electrospray tandem mass spectrometry (HPLC-ESI-MS/MS) assay for the determination of levetiracetam in human matrix (plasma, serum, or saliva).

METHODS

An API-3000 or API-4000 triple-quadrupole mass spectrometer (Sciex, Concord, Canada) coupled with the IonSpray source and Shimadzu HPLC system (Shimadzu Scientific Instruments, Columbia, MD) was used employing ritonavir as internal standard (IS) for levetiracetam. One hundred microliters of serum (or plasma, saliva) was deproteinized by adding 150 microl of acetonitrile containing internal standard. After centrifugation, 100 microl of supernatant was diluted with 300 microl of water and 10 microl aliquot was injected onto a C-18 column. After a 2.5 min wash the valve was activated to initiate the isocratic elution program which eluted the levetiracetam and internal standard into the MS/MS system. Quantitation by MRM analysis was performed in the positive ion mode. Within-day and between-day imprecision were evaluated for levetiracetam using three levels of in-house controls. Reliability and accuracy of this method were assessed by comparison of targets with external QC material (ChromSystems), between laboratory comparisons and by recovery studies.

RESULTS

Within-day coefficients of variation (CVs) were <6.1% and between-day CVs were <8.2%. The average spiked recoveries of levetiracetam added to the drug-free human plasma samples were 108% at low concentration level and 103% at high concentration level.

CONCLUSIONS

The method was found both specific and sensitive for the rapid and accurate measurement of levetiracetam in human matrices and correlated well with the Quest/Chantilly tandem mass spectrometric method (r=0.983).

A validated chiral liquid chromatographic method for the enantiomeric separation of Rivastigmine hydrogen tartarate, a cholinesterase inhibitor

A new and accurate chiral liquid chromatographic method was developed for the enantiomeric resolution of Rivastigmine hydrogen tartarate, (-)S-N-ethyl-3-[(1-dimethyl-amino)ethyl]-N-methylphenyl-carbamate hydrogen tartarate, a cholinesterase inhibitor in bulk drugs. The enantiomers of Rivastigmine hydrogen tartarate were baseline resolved on a Chiralcel OD-H (250 mm x 4.6 mm, 5 microm) column using a mobile phase system containing hexane: isopropanol: trifluoroacetic acid (80:20:0.2, v/v/v). The resolution between the enantiomers was not less than four and interestingly distomer was eluted prior to eutomer in the developed method. The presence of trifluoroacetic acid in the mobile phase has played an important role in enhancing chromatographic efficiency and resolution between the enantiomers. The developed method was extensively validated and proved to be robust. The limit of detection and limit of quantification of (R)-enantiomer were found to be 500 and 1500 ng/ml, respectively for 10 microl injection volume. The percentage recovery of (R)-enantiomer was ranged from 95.2 to 104.3 in bulk drug samples of Rivastigmine hydrogen tartarate. Rivastigmine hydrogen tartarate sample solution and mobile phase were found to be stable for at least 48 h. The proposed method was found to be suitable and accurate for the quantitative determination of (R)-enantiomer in bulk drugs. Chiralcel OJ-H column can also be used as an alternative for the above purpose.