Successful management of discovered pH dependence in vancomycin recovery studies: novel HPLC method for microdialysis and plasma samples.

Vancomycin is a glycopeptide antibiotic approved for the treatment of serious infections or patients allergic to beta-lactams. A rapid HPLC assay using UV detection for the determination in microdialysate and human plasma was developed. After sample preparation, using methanol and trichloroacetic acid for plasma and water for microdialysate, 20 microL were injected and separated on a RP(18) column. Overall, the assay exhibited good precision and accuracy. The diffusion properties of vancomycin investigated in in vitro microdialysis experiments revealed an unfavourable concentration dependence avertable by keeping a constant pH using phosphate buffer as perfusate. The mean relative recoveries were 27.8% [coefficient of variation (CV) 11.1%] and 33.2% (CV 8.3%) for retrodialysis and recovery experiments, respectively. Following characterization of vancomycin in in vitro microdialysis, the developed setting is suitable for application in (pre-)clinical studies.