Development of an Analytical UHPLC Method for the Estimation of Cyclosporine in SMEDDS and Protein Binding

Aim of present study was to develop a simple, precise and accurate LC-UV method for the cyclosporine A (CyA) estimation in microemulsion formulation and in vitro release samples in phosphate buffer pH 6.8. CyA was separated on Hibar® 250-4,6 LiChrospher® 100 RP-18e (5μm) column at 70oC with 1mL/min flow rate using acetonitrile:methanol:water (pH=3.5 with 0.5% orthophosphoric acid) :: 65:25:10 as mobile phase and methanol as diluent. The method successfully resolved the co eluting peaks obtained during in vitro release study samples with reproducible retention time of CyA. The drug content was also analyzed during thermodynamic stability testing of formulation and was found to be 98.13 ± 2.29%. The protein binding affinity of CyA was estimated to be 98.95 ± 0.1%. A validated method was used for quantification of free drug and bound drug using albumin as protein substrate. Protein binding affinity of drug was assessed using standard equilibrium dialysis method and protein binding characteristic was studied using Scatchard plot. The newly developed method is suitable for accurate estimating of CyA in self emulsifying microemulsions and hence proving its clinical potential.