A rapid liquid chromatographic method for the determination of lamotrigine in plasma

A rapid,sensitive and simple high-performance liquid chromatographic (HPLC) method for the determination of lamotrigine in plasma is described. The drug was extracted from 100 mu l of plasma with chloroform: isopropanol (95:5% v/v) in the presence of 100 mu l of phosphate buffer (10 mM). The extract was evaporated and the residue was reconstituted with mobile phase and injected onto the HPLC system. The drug and the internal standard (chloramphenicol) were eluted from a Symmetry C-18 stainless steel column at ambient temperature with a mobile phase consisting of 0.01 M potassium phosphate-acetonitrile-methanol (70:20:10% v/v/v), adjusted to pH 6.7, at a flow rate of 1.3 ml min(-1) and the detector was monitored at 214 nm. Quantitation was achieved by measurement of the peak-area ratio of the drug to the internal standard and the lower limit of detection for lamotrigine in plasma was 20 ng ml(-1). The intraday precision ranged from 3.34 to 6.12% coefficient of variation (CV) and the interday precision ranged from 2.15 to 8.34% CV. The absolute and relative recoveries of lamotrigine ranged from 86.93 to 90.71% and from 95.18 to 107.13%, respectively. The method was applied in studying the pharmacokinetics of lamotrigine administered orally to rabbits. This reliable micro-method would have application in pharmacokinetic studies of lamotrigine where only small sample sizes are available, e.g. paediatric patients. (C) 1998 Elsevier Science B.V. All rights reserved

Quantitative determination of clavulanic acid in plasma by HPLC: Application to a pharmacokinetic study

A rapid, simple, accurate, sensitive, and reproducible high performance liquid chromatographic (HPLC) method for quantification of clavulanic acid (CA) in human plasma using metronidazole as an internal standard has been developed and validated. Following derivatization with imidazole, plasma protein was precipitated using acetonitrile. The drug and the internal standard were eluted from a 4-mum stainless steel Novapak(R) C-18 column (150 x 3.9 mm(2) I.D.) at room temperature, with a mobile phase consisting of 4% methanol in 0.01 M potassium dihydrogen phosphate buffer (pH adjusted to 3.2), at a flow rate of 1.8 mL/min. The effluent was monitored using a UV detector set at 3 11 nm. Each analysis required no longer than 8 min. Quantitation was achieved by measurement of the peak height ratio of the drug to the internal standard, and the limit of quantification of CA in plasma was 100 ng/mL. The intraday coefficient of variation (C.V., %) ranged from 3.30% to 3.93% and interday C.V. ranged from 1.74% to 2.74% at three different concentrations. The mean relative recovery was 100.35% and the mean absolute recovery was 97.63%. A stability test shows that CA is stable in plasma for at least 4 weeks when stored at -70degreesC. The method was successfully applied in a bioavailability/bioequivalence study involving amoxicillin/CA combination (250/62.5 mg) administered orally to 24 healthy volunteers