In-vitro protein binding interaction between a metabolite of triflusal, 2-hydroxy-4-trifluoromethylbenzoic acid and other drugs.

2-Hydroxy-4-trifluoromethylbenzoic acid (HTB) is the main active metabolite of triflusal, an antiplatelet drug. The in-vitro binding of HTB to human serum was studied in the presence of different drugs. The results indicate that no statistically significant changes are observed in the HTB binding in the presence of caffeine, theophylline, glisentide, enalapril, cimetidine or warfarin. The free fraction of HTB increases significantly in the presence of the non-steroidal anti-inflammatory drugs studied: diclofenac, ibuprofen, indomethacin, naproxen, piroxicam and salicylic acid. At high concentrations, HTB displaces these anti-inflammatory drugs and also glisentide and warfarin from their protein binding sites.