Abstract
The measurement of the uniformity of preparations is an important component of quality assessment. This study was conducted to evaluate the appropriate mixing time for external preparations using a planetary centrifugal mixer. Steroid ointment and white petrolatum (5 g each) were added to a 13-mL container and mixed using a planetary centrifugal mixer (NRE-120®, THINKY) at a rotation speed of 800 rpm and a revolution speed of 2000 rpm. We sampled 0.1 g of the mixture from three spots (the top, the middle, and the bottom portions) of the container, measured the steroid content, and evaluated the product uniformity of mixtures of ten different steroid ointments (Dermovate®, Antebate®, Myser®, Nerisona®, Methaderm®, Rinderon®-VG, Lidomex®, Almeta®, Kindavate®, and Locoid®) with white petrolatum (Propeto®). Our results showed that when the coefficient of variation (CV) is less than 15.2％, a mixing time of at least 60 seconds is required to achieve proper mixing to obtain the permissible limit of steroid ointment and white petrolatum, and the greater the difference of the yield point between steroid ointment and white petrolatum the easier mixing was. These results suggest that the spreadability of ointment affects the mixing efficiency of a planetary centrifugal mixer.
