Hot-melt sub- and outercoating combined with enteric aqueous coating to improve the stability of aspirin tablets

Aspirin is apt to hydrolyze. In order to improve its stability, a new method has been developed involving the application of hot-melt sub- and outercoating combined with enteric aqueous coating. The main aim was to investigate the influence of these factors on the stability of ASA and understand how they work. Satisfactory storage stability were obtained when the aspirin tablet core coated with Eudragit L30D55 film was combined with glycerin monostearate (GMS) as an outercoat. Hygroscopicity testing indicated that the moisture penetrating into the tablet may result in a significant change in the physical properties of the coating film observed by scanning electron microscopy. Investigation of the compatibility between the drug and film excipients shows that the talc and methacrylic acid had a significant catalytic effect on ASA. A hypothesis was proposed that the hydrolysis of ASA enteric coated tablets (ASA-ECT) was mostly concentrated in the internal film and the interfaces between the film and tablet core. In conclusion, hot-melt coating technology is an alternative to subcoating or outercoating. Also, GMS sub-coating was a better choice for forming a stable barrier between the tablet core and the polymer coating layer, and increases the structure and chemical stability.

Graphical AbstractAspirin enteric-coated tablets were successfully prepared to avoid drug migration and enhance the stability of ASA involving combination of a GMS hot-melt coat with a level of 2% (w/w) and an acrylic resin polymer coat of 6% (w/w). In addition, systematic investigations to the interaction between the film components and ASA and the corresponding hydrolysis mechanism in ASA enteric-coated tablets were performed. The in vitro dissolution of a double-coating system was also assessed, compared with a conventional single-coating.74