Comparative static curing versus dynamic curing on tablet coating structures

Abstract

Curing is generally required to stabilize film coating from aqueous polymer dispersion. This post-coating drying step is traditionally carried out in static conditions, requiring the transfer of solid dosage forms to an oven. But, curing operation performed directly inside the coating equipment stands for an attractive industrial application. Recently, the use of various advanced physico-chemical characterization techniques i.e., X-ray micro-computed tomography, vibrational spectroscopies (near infrared and Raman) and X-ray microdiffraction, allowed new insights into the film-coating structures of dynamically cured tablets. Dynamic curing end-point was efficiently determined after 4h. The aim of the present work was to elucidate the influence of curing conditions on film-coating structures. Results demonstrated that 24h of static curing and 4h of dynamic curing, both performed at 60°C and ambient relative humidity, led to similar coating layers in terms of drug release properties, porosity, water content, structural rearrangement of polymer chains and crystalline distribution. Furthermore, X-ray microdiffraction measurements pointed out different crystalline coating compositions depending on sample storage time. An aging mechanism might have occur during storage, resulting in the crystallization and the upward migration of cetyl alcohol, coupled to the downward migration of crystalline sodium lauryl sulfate within the coating layer. Interestingly, this new study clearly provided further knowledge into film-coating structures after a curing step and confirmed that curing operation could be performed in dynamic conditions.

Characterization of Pharmaceutical Tablets by X-ray Tomography

“…However, for coated tablets, after compression the tablets are subjected to a coating process. The coating is carried out for example by spray coating followed by a drying process that can typically induce mechanical and thermal stress on the tablet potentially affecting the compaction and integrity of the tablet [ 198 , 199 ]. Therefore, the compression step is a crucial stage in tablet manufacturing as all the other characteristics of the tablet can be affected by this step.…”

“…Critical parameter of the coating layer is the coating thickness uniformity and their distribution. The thickness of the coating layer can typically vary from 5 to 100 m [ 198 ], and the uniformity of the coating layer is affected during the coating process [ 199 , 320 , 321 ]. The performance and the quality of the coating layer can also be determined by simulation and modelling tools such as discrete element method, and can be used to optimize the coating process [ 322 ].…”

“…The performance and the quality of the coating layer can also be determined by simulation and modelling tools such as discrete element method, and can be used to optimize the coating process [ 322 ]. The tablet coating involves spraying of the coating material in the liquid form by constantly mixing/rotating the container with the tablets, followed by a drying process [ 198 , 199 ]. Possible sources of defects include the formation of pores, cracks or clustering of the materials at a particular region [ 198 ].…”

Towards a Better Understanding of Verapamil Release from Kollicoat SR:IR Coated Pellets Using Non-Invasive Analytical Tools

“…The chemical composition of the polymeric membrane, its thickness and inner structure, but also the type of core material can have a major impact on the relative importance of the involved physico-chemical phenomena [ 19 , 28 , 29 ]. Different studies focus on the evaluation of the properties of the polymeric film coatings using a variety of in-, on- or off-line tools [ 30 , 31 , 32 ]. Polymeric film coatings can be either applied from organic solutions or aqueous dispersions [ 33 , 34 , 35 , 36 ].…”