The influence of cetomacrogol ointment processing on structure: A definitive screening design

Batch-to-batch variability is a challenge for the industrial scale production of ointments. Therefore the current investigation focussed on identifying and understanding critical process parameters (CPPs) for cetomacrogol ointment. This was evaluated using a definitive screening design (DSD) approach in which fourteen batches were produced under predefined and controlled conditions using the following variables: addition of SiO2 nanoparticles, mixing speed, cooling rate, heating temperature, container filling temperature and isothermal mixing at the filling temperature. Ointment structure was evaluated using a number of rheological parameters. One of these parameters, yield stress was found to be strongly influenced by filling temperature and mixing speed (p = 0.0065 and p = 0.0013 respectively). Both significantly affect ointment structure and they also have a significant interaction (p < 0.05). Understanding the ointment production process can help in defining a processing window to produce ointment of constant quality.