Two highly sensitive, rapid, simple, economic and validated spectrofluorimetric methods have been developed for determination of Topiramate and Levetiracetam in pharmaceutical tablets and in human plasma. Topiramate and Levetiracetam were determined separately by derivatization using 4-Chloro-7-nitrobenzofuran-2-oxo-1,3-diazole (NBD-Cl) and measured spectrofluorimetrically. The Relative fluorescence intensities were measured at λem/ex of 547/465 nm and 551/465 nm for Topiramate and Levetiracetam, respectively. While a binary mixture of Topiramate and Levetiracetam were determined by the fourth derivative synchronous fluorescence measurement after their reaction with NBD-Cl. In this method, the fourth derivative synchronous spectra were estimated as peak to peak measurement at 493-497 and 490.5-495 nm corresponding with zero-contribution of Levetiracetam and Topiramate, respectively. Linearity ranges for Topiramate and Levetiracetam in both methods were found to be 0.15-1.2 and 0.2-1.5 μg/mL, respectively. The different experimental parameters affecting the fluorescence of the two drugs were carefully studied and optimized. The proposed methods were validated in terms of linearity, accuracy, precision, limits of detection and quantification and other aspects of analytical validation. The proposed methods were successfully applied for the determination of the investigated drugs in human plasma samples obtained from healthy volunteers after single oral administration of the two drugs.
The method was proved to be linear in the range of 0.5-50 µg/ml for all drugs. It was successfully applied for clinical PK study of the AEDs in healthy volunteers following single administration. Also, this method was applied for simultaneous determination of the studied drugs in volunteers' plasma receiving synergistic binary combinations from the four AEDs when used as add-on therapy. The good precision and selectivity of the developed method allow it to be used for routine therapeutic drug monitoring of such drugs as a useful tool in epilepsy management.
Summary. Incidence of suicidal attempts presents an explanation for the high prevalence of quetiapine (QTI) in forensic cases. Thus, the interpretation of its concentrations in biological specimens is needed, but in forensic toxicology, potential postmortem changes such as instability of the target drugs should be taken in consideration. Highperformance liquid chromatography (HPLC) method has been developed for determination of QTI. This method was based on reversed phase (RP)-HPLC separation of QTI on a C-18 column (150 mm × 4.6 mm, 5 μm) with elution system of acetonitrile-methanol-0.025 M phosphate buffer (pH 2.5), containing 1 mL TEA in each 250 mL, in a ratio of 40:30:30%, v/v, at the flow rate of 1.2 mL min −1 using mirtazapine as internal standard (IS). The proposed method was applied to the determination of QTI in plasma in presence of coadministered drugs. The application of the proposed method was extended for long-term stability study of two different concentration levels of QTI in the whole blood.
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