Journal of Pharmaceutical and Biomedical Analysis 28 (2002) 181–186 Short Communication LC determination of praziquantel in human plasma Wibool Ridtitid *, Malinee Wongnawa, Werawath Mahatthanatrakul, Jarurat Punyo, Methi Sunbhanich Department of Pharmacology, Faculty of Science, Prince of Songkla Uniersity, Hat Yai, Songkla 90112, Thailand Received 3 August 2001; received in revised form 4 September 2001; accepted 8 September 2001 Abstract A simple high-performance liquid chromatographic (HPLC) method for the determination of praziquantel in human plasma was developed and validated. The present method was described by adding drop-wise 0.2 M Zinc sulfate and acetonitrile to plasma sample for deproteinization. This method used a reversed-phase Spherisorb ODS 2 column (5 m), 250 ×4.6 mm i.d. as a stationary phase with a mobile phase consisting of acetonitrile- methanol-water (36:10:54, v/v/v), a flow rate of 1.5 ml/min and UV detection wavelength of 217 nm. Diazepam was used as internal standard. The standard calibration curve was linear over the concentration range of 100 – 2000 ng/ml (r =0.999). The equation of a linear regression line was y =8.05E-04 +7.25E-04x with slope and intercept values of 0.0007 and 0.0008, respectively. The limit of detection was 12.25 ng/ml and the limit of quantification was set at 100 ng/ml. The intra- and inter-day assay coefficients of variation (CV) were 3.0 1.7 and 6.3 1.9%, respectively. The percentage of recovery was 102.1 5.6. Therefore, the HPLC method described here was simple, rapid and reproducible since it did not require extraction and evaporation processes in sample preparation, which will reduce time-consuming or expensive sample preparation. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Praziquantel; High-performance liquid chromatography; Reversed-phase HPLC www.elsevier.com/locate/jpba 1. Introduction Praziquantel, a pyrazinoisoquinoline derivative, has a wide range of activity against trematodes and cestodes, and is widely used in schistosomia- sis, as well as other fluke infections pathogenic to humans [1]. Praziquantel is readily absorbed after oral administration, even when taken with a meal, so that peak plasma levels in humans occur in 1–2 h. The drug is about 80% bound to plasma proteins. Its plasma half-life is 0.8 – 2 h, compared with 4–6 h for its metabolites. About 70% of an oral dose of praziquantel is recovered as metabo- lites in the urine within 24 h [2]. However, more than 80% of the dose is absorbed with 80% of an oral dose excreted as hydroxylated metabolites in urine within 4 days [1]. Advantages of this agent include high efficacy after oral administration, low toxicity and a single day therapeutic regimen. * Corresponding author. Tel./fax: +66-74-446678. E-mail address: rwibool@ratree.psu.ac.th (W. Ridtitid). 0731-7085/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved. PII:S0731-7085(01)00605-7