A sensitive HPLC-UV method for quantifying vancomycin in biological matrices: Application to pharmacokinetic and biodistribution studies in rat plasma, skin and lymph nodes.

Vancomycin (VCN) is an antibiotic used in the treatment of methicillin-resistant Staphylococcus aureus (MRSA)-derived infections. As it has a relatively narrow therapeutic window, it is imperative to develop a sensitive and reliable analytical method for drug monitoring and pharmacokinetic purposes. In the present study, quick sample preparations and a sensitive high-performance liquid chromatography method using UV detection (HPLC-UV) have been developed and validated. The analytical method for detection and quantification of VCN in rat plasma, skin and lymph node samples was validated based on the Food and Drug Administration (FDA) and European Medicine Agency (EMEA) bioanalytical method validation guidelines. The optimised plasma sample preparation involved a simple protein precipitation step, with extraction recovery of 100.3 ± 0.92 %. VCN in all biological matrices was analysed in a HPLC-UV system (215 nm) using a Cortecs® C18 column (4.6 × 150 mm, 2.7 μm particle size) fitted with a guard cartridge set at 20 °C. Reverse phase HPLC under gradient conditions, with mobile phase consisting of 20 mM phosphate buffer containing 0.5 % v/v of triethylamine and a mixture of methanol - acetonitrile (70:30, v/v), and runtime of 12 min/sample was employed. The calibration standards used for plasma ranged between 0.1-50 μg/ml, while in the skin and lymph node matrices, standards ranged between 0.05-50 μg/ml with correlation coefficients (R2) of ≥ 0.9995 for all matrices. The method was selective, sensitive, accurate and precise for detecting and quantifying VCN in the biological matrices used. The validated method was successfully utilised in the detection of VCN in a pharmacokinetic and organ biodistribution study carried out in rats following oral and IV bolus administration of the drug. This validated bioanalytical method offers a wide range of potential applications in clinical therapeutic drug monitoring, pharmacokinetics and toxicology.