Determination of drug-polymer binding constants by affinity capillary electrophoresis for aryl propionic acid derivatives and related compounds.

The binding constants (K(b)s) of 17 aryl propionic acid derivatives (APADs) and related compounds with polyvinylpyrrolidone (PVP K30) and vinylpyrrolidone-vinyl acetate copolymer (Kollidon VA64) in aqueous media were determined by affinity capillary electrophoreses (ACE). The K(b)s of APAD to polymers increase with octanol-water partition coefficients of the compounds. Kollidon VA64 is a stronger binder than PVP K30 to APAD compounds. The K(b)s are greater at pH 4 than at pH 9. Both hydrophobic interaction and hydrogen bonding may be involved. However, hydrophobic interaction appears to be dominant. The ACE method is simple and fast, which could be used to study drug-polymer interaction in aqueous media.