DOI: 10.36347/sajp

Pages: 87-91

Ebastine (EBA), 4'-tert-butyl-4-(4-(diphenyl methoxy) piperidino) butyrophenone, is a second generation H1- antihistamine. The solubility of EBA is poor in aqueous solutions, but increases in acidic conditions. EBA is degraded in aqueous solutions. There are no reports about the degradation rate of EBA in acidic solutions. The aim of this study was to determine the degradation rate of EBA in an acidic solution and to stabilize EBA in the solution. The stability of EBA in a buffer solution at pH 1.2 with 1% methanol at 37, 50 and 60°C was examined. EBA in solution was determined by HPLC. α-, β- and γ-cyclodextrins (CDs) as stabilizers as well as the stability of the CDs in solution were examined. The degradation of EBA was considered to be a pseudo-first-order reaction. The apparent first-order rate constant of EBA in the pH 1.2 buffer solutions at 37°C was 14.9×10-3 hour-1. When α-, β- and γ- CDs were added, the rate constant decreased to 12.2×10-3, 0.83×10-3 and 7.20×10-3 hour-1 for α-, β- and γ- CDs, respectively. β- CD was found to have the strongest stabilizing effect. The activation energy for the degradation of EBA under this condition was 106.9 kJ/ mol. The addition of CDs increased the value, and CDs were slowly degraded in the pH 1.2 solution