Impact of the curing parameters on drug release from Eudragit RS and RL 30D coated pellets: Design of experiments

Polymethacrylate polymers are commonly used for the coating of prolonged-release pellets. Due to environmental and other concerns, aqueous latex dispersions are preferred over organic solutions. When using aqueous dispersions, a curing step is needed to ensure complete film formation. The aim of the present work was to investigate the impact of the curing process parameters on diclofenac sodium release from pellets coated with Eudragit RS and RL 30D. The design of experiments took three factors (temperature, time and relative air humidity) into consideration and was used to study the effect of these single factors as well as factor interactions on the amount of released diclofenac sodium and loss on drying of cured pellets. The results suggested that all parameters have an effect on the amount of released diclofenac sodium. A positive effect of time and temperature was observed on film formation at low to moderate relative air humidity (decreasing drug release). On the other hand, when using high relative humidity, an increase in curing time and temperature led to accelerated drug release. These phenomena were further studied and results suggested that long curing times in combination with high temperature and high humidity caused drug diffusion into the film coating.

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