Protein binding of acetylsalicylic acid and salicylic acid in porcine and human serum.

As part of a pilot project establishing a porcine model for aspirin overdose, the percentage protein binding of acetylsalicylate (ASA) and salicylate (SA) in porcine and human sera was evaluated in vitro over a range of concentrations. Serum from 2 pigs and 4 humans were spiked with ASA concentrations of 0.5-100 mg/dL and SA concentrations of 1-120 mg/dL. Protein binding for each concentration of ASA and SA was determined using radiolabeled drug and ultrafiltration with the Centrifree micropartition system. The percentage protein binding for ASA in pig and human sera were similarly low (< 50%) for all concentrations evaluated. Percentage protein binding for SA for pig and human sera were high (approximately 90% and 80%) at low therapeutic concentrations, but then declined to approximately 30% at higher toxic concentrations (120 mg/dL). The protein binding of ASA and SA over a range of concentrations was similar for porcine and human sera.