title: Determination of atypical nonlinear plasma−protein-binding behavior of tigecycline using an in vitro microdialysis technique.
abstract: Tigecycline, a novel glycylcycline antibiotic, shows atypical nonlinear plasma-protein-binding behavior using ultrafiltration and ultracentrifugation techniques. The mechanism of such counterintuitive behavior is currently unknown. Ultrafiltration and ultracentrifugation cause fractional change in protein concentration and therefore may influence plasma-protein binding. Microdialysis (MD), a novel technique, can sample unbound drugs without any change in fractional protein concentration. To determine whether the atypical nonlinear plasma-protein-binding behavior is not related to measurement technique, the plasma-protein binding of tigecycline was determined using MD. A sensitive liquid chromatography-mass spectrometry method was developed and validated for the bioanalysis of tigecycline in the dialysate. The probe recoveries and plasma-protein binding of tigecycline at four different concentration levels 0.1, 1, 10, and 100 μg/mL were determined. Similar to ultracentrifugation and ultrafiltration, MD also showed atypical nonlinear plasma-protein-binding behavior of tigecycline up to 10 μg/mL, but unbound fraction increased at 100 μg/mL indicating saturation of mechanism responsible for atypical nonlinear behavior. This study concludes that the atypical nonlinear binding behavior of tigecycline is not technique-dependent, rather it is a true behavior of tigecycline. Further investigations are necessary to elucidate the mechanism.
authors.affiliation: Department of Pharmaceutics, College of Pharmacy, University of Florida, Gainesville, Florida, 32610.
authors.forename: Jatinder Kaur
authors.initials: JK
authors.lastname: Mukker
authors.forename: Ravishankar Prasad
authors.initials: RP
authors.lastname: Singh
authors.forename: Hartmut
authors.initials: H
authors.lastname: Derendorf
mesh_terms: D000900:Anti-Bacterial Agents / Q000032:analysis / Q000378:metabolism*; D001798:Blood Proteins / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D004355:Drug Stability; D006801:Humans; D057230:Limit of Detection; D017551:Microdialysis; D008911:Minocycline / Q000031:analogs & derivatives* / Q000032:analysis / Q000378:metabolism; D009994:Osmolar Concentration; D011485:Protein Binding; D015203:Reproducibility of Results; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry; D000078304:Tigecycline
chemical_list: D000900:Anti-Bacterial Agents; D001798:Blood Proteins; D000078304:Tigecycline; D008911:Minocycline
keywords: atypical nonlinear plasma-protein binding; bioanalysis; liquid chromatography; mass spectrometry; microdialysis; protein binding; tigecycline