Temperature Dependence of Bimolecular Reactions Associated with Molecular Mobility in Lyophilized Formulations

Purpose. We studied the temperature dependence of acetyltransfer between aspirin and sulfadiazine, a bimolecular reaction, inlyophilized formulations at temperatures near the glass transitiontemperature (Tg) and NMR relaxation-based critical mobilitytemperature (Tmc), to further understand the effect of molecularmobility on chemical degradation rates in solid pharmaceutical formulations.The temperature dependence of the hydrolysis rates of aspirin andcephalothin in lyophilized formulations was also studied as a model ofbimolecular reactions in which water is a reactant.