The theoretical onset were determined by DSC (Q-2000, TA Instruments, New Castle, DE, USA) as described elsewhere. The onset temperature of the heating rates were extrapolated to a heating rate of 0 °C min -1 . The extrapolated value corresponds to the respective onset temperature of the dissolution process for the three drug loadings of celecoxib in PVP. It should be noted that the determined temperatures correspond to water-free systems; and these will be lower for formulations that still contain small amounts of sorbed water due to the hygroscopicity of the polymer PVP.