Study of the mechanism of cationic drug release increase coated with Surelease® after curing

This paper describes the investigation of the release mechanism of the cationic drug coated with Surelease® after curing compared with nonionic and anionic drug. The release rate of cured propafenone hydrochloride pellets coated with Surelease® was increased significantly compared with uncured ones. The changes in release rate after seal-coating proved the migration of drug into the polymer film. Based on a comparative study of ammonia permeation tests and the impact of ammonia on drug with different properties, it was shown that the change in release of the cationic drug after curing was related to the combination of cationic drug and ammonia in Surelease®. Also, the scanning electron microscopy results showed that curing and dissolution can both prevent polymer film coalescence. During coating, the evaporated ammonia combined with the cationic drug and the polymer film coalesced. However, the combined ammonia could be decomposed during curing and interrupt the coalescence of the polymer-coat, leading to increased release. In an optimized process, the ammonia in the Surelease® can be evaporated quickly and the ionization of the drug will be reduced. All these factors can contribute to the formation of the polymer film.