Rationale: In order to characterize the intracellular pharmacokinetic properties of tigecycline, we developed and fully validated a liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for quantification of tigecycline in human lung epithelial (BEAS-2B) cells and polymorphonuclear neutrophils (PMNs).
Methods: Tetracycline was used as an internal standard and chromatographic separation was achieved on a C18 Hypersil Gold aQ column using two mobile phases, a solution of water (containing 0.1% formic acid) and acetonitrile. The flow rate was 0.4 mL/min for 5.0 min. Tigecycline drug uptake was evaluated by incubating the BEAS-2B cells and the PMNs for up to 3 h at tigecycline concentrations of 1 mg/L.
Results: The assay was linear over the tested concentration range of 0.01-2 mg/L for tigecycline in BEAS-2B cells and PMNs (r2 >0.99). The inter- and inter-day precisions (RSD, %) were <10.02% and the accuracies (%) were within the range of 85-115%. The uptake study showed that after incubation with tigecycline (1 mg/L) for 3 h at 37°C, the intracellular peak concentration of BEAS-2B cells was 14.44 ± 7.12 mg/L at 1 h, and 41.43 ± 25.66 mg/L in PMNs at 20 min. The mean intracellular concentrations fluctuated in the range of 0.8-14.44 mg/L in BEAS-2B cells and 10.14-41.43 mg/L in PMNs for 1 mg/L tigecycline exposure.
Conclusions: Validated LC/MS/MS is a simple, rapid, and sensitive method for determining the intracellular concentration of tigecycline, and tigecycline has good penetrations both in human BEAS-2B cells and PMNs. The method can be efficiently used for future studies of the intracellular pharmacokinetics of tigecycline.
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