Hot-melt coating of hydrosensitive products

PACHECO, CONSUELO; KHOUFECH A. ; PIÑA, JULIANA; SALEH, KHASHAYAR

Sheffield

Workshop; 6th International Granulation Workshop 2013; 2013

Sheffield University

The main objective of coating pharmaceutical dosage forms is to achieve superior aesthetic quality (e.g. colour, texture, and taste), physical and chemical protection, or to modify drug release characteristics [1]. Among the coatings geared towards attaining controlled release of active principles, enteric coatings are applicable in cases where release must occur at intestinal level. Different approaches have been used to fulfil this goal, although, so far, pH-dependent systems have found practical application [2]. Most commonly used pH-dependent coating polymers are methacrylic acid copolymers [2], being applied mostly from aqueous dispersions. The survival of a number of yeast powders (e.g. Saccharomyces Boulardii which is an anti-diarrhoeal agent) is challenged after oral administration, being less than one per cent of the live yeast administered orally recovered in faeces [3]. Therefore, enteric coatings emerge as an interesting alternative to protect them from gastric acidic conditions. It has been also proved that the viability of yeast cells drastically decreases when they are exposed to high relative humidity atmospheres, in combination with high temperatures [3]. Consequently, direct coating with an aqueous dispersion would lead to a loss of viable cells during the process. In the present work, a two layer coating system is proposed to improve the delivery of S. boulardii to the intestine: the first layer acting as a protection barrier against moisture and the second one imparting enteric properties. For the former, hot melt coating -consisting in the application of a molten material over the substrate to be coated, followed by a solidification step upon cooling- was applied. Three different materials were selected: stearic acid, polyethylene glycol and poly(ethylene oxide)-poly(propylene oxide) block copolymers. Coating of model particles -glass beads and sodium chloride particles- was carried out in a 1 L fluidized bed. The effect of different process parameters such as the difference between bed and liquid temperatures, excess fluidization velocity, and particle and droplet size on the agglomeration rate and coating efficiency was evaluated. Special emphasis was done to establish the relationship between the behaviour of liquid droplets at micro-level and the process performance.