Analysis of an anti-inflammatory steroidal drug, difluprednate, in aqueous humor by combination of semi-micro HPLC and column switching method.

A specific and sensitive method for the determination for difluprednate (DFBA) and its metabolite (deacetylated DFBA, DFB) in aqueous humor was developed. DFBA and DFB were initially absorbed on a Pinkerton-type column, then analyzed by high-performance liquid chromatography using a semi-micro column after column switching. Under the optimized conditions, calibration curves for DFBA and DFB showed good linearity over the range of 1.0-50 and 0.5-50 ng/ml, respectively. We applied the method to the analysis of DFBA and DFB in rabbit aqueous humor, and found that DFBA in rabbit aqueous humor 1 h after instillation of 0.002% DFBA ophthalmic emulsion was not detected, but DFB was present at the concentration of 4.3+/-3.1 ng/ml.