Determination of cefadroxil in rat plasma and urine using LC-MS/MS and its application to pharmacokinetic and urinary excretion studies

Abstract

A simple, rapid, and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed and validated for the determination of cefadroxil, a first-generation cephalosporin, in rat plasma and urine. Rat samples were deproteinized with methanol, and then injected into the LC-MS/MS system (electro-spray ionization, positive mode) for quantification. Drugs were separated on a Synergi™ 4 μm Polar-RP 80A column (150 mm × 2.0 mm, 4 μm) with a mixture of 0.1% formic acid and methanol (62:38, v/v) as the mobile phase at 0.2 mL/min. Detection was performed using multiple reaction-monitoring modes at m/z 364.1→208.1 (for cefadroxil) and m/z 368.1→174.2 (for cefaclor, the internal standard). Method was specific and linear over the concentration range of 10-10,000 ng/mL. Validation parameters for cefadroxil, including accuracy, precision, absolute matrix effect, and stability in rat plasma and urine, were acceptable according to the biological method validation guidelines of the FDA (2001) [16]. Cefadroxil levels in plasma up to 1440 min or 480 min and urine up to 96 h were quantifiable following oral and intravenous cefadroxil administrations to rats at a dose of 2mg/kg, each, suggesting that the method is appropriate for routine pharmacokinetic studies including urinary recovery in rats.

Keywords: AUC; AUC(∞); AUMC(∞); C(max); Cefadroxil; ESI; HPLC; LC–MS/MS; LOD; LOQ; MRM; MS/MS; Pharmacokinetics; Plasma; QC; RSD; Rat; SPE; T(max); Urine; area under the first moment–time curve from time zero to infinity; area under the plasma concentration curve; electro-spray ionization; high-performance liquid chromatography; limit of detection; limit of quantification; multiple reaction monitoring; peak plasma concentration; quality control; relative standard deviation; slope of the log-linear portion of the concentration time profile; solid-phase extraction; t(1/2); tandem mass spectrometry; terminal phase half-life; time to reach C(max); total area under the plasma concentration–time curve from time zero to infinity; λ.