A validated HPLC method for zanamivir and its application to in vitro permeability study in CACO-2 culture model

A simple HPLC method was developed and validated for the quantification of zanamivir in permeability studies using Caco-2 cell culture model. Chromatographic resolution was achieved using 98% (v/v) ultrapure water and 2% (v/v) acetonitrile as mobile phase with flow rate of 0.5 ml/min on a BDS Hypersil Cyano column (length 250 mm; internal diameter 4.6 mm; particle size 5 μm) and UV detection at 230 nm. The method was linear for the quantification of zanamivir at concentration ranging from 0.1-10 μg/ml with coefficient of determination greater than 0.999. The recovery of zanamivir was in the range of 99.76-105.08%. The relative standard deviations of the within-day precision and between-day precision were lower than 10.32 and 14.33%, respectively. The permeability of zanamivir was independent of the transport direction and zanamivir concentrations, indicating a passive transport of zanamivir across Caco-2 cells. With the absence of Ca(2+) in transport medium, the permeability values of zanamivir increased 56.21 and 57.20 fold in the directions of apical to basolateral and basolateral to apical, respectively. On the basis of these results, zanamivir was found to be predominantly transported across Caco-2 monolayers via the passive paracellular pathway.