Enteric Coating Polymers Past and Present - A review

Tablet coating has evolved over the years and today, there are various types of coating for delayed release of a drug. Drugs can be enteric-coated to provide delayed release, protect the active pharmaceutical ingredients, minimize undesirable effects, and modify the pharmacokinetic properties of a drug, which will have clinical impacts. There are certain types of drugs that need to be enteric coated due to various reasons, such as it being a gastric irritant or it being acid liable. This article will review ethylcellulose and polymethacrylate, their role in an enteric coating, and their process coating parameters. Ethylcellulose can be used to provide a short delayed release; it can be modified by adding pH-dependent polymers such as sodium alginate and hydroxypropyl methylcellulose phthalate for a long delayed release. On the other hand, polymethacrylate can also be employed to enteric coat drugs without additional polymers. Polymethacrylate such as Eudragit comes in different grades with varying proportions of polymer ratio, allowing for targeted delayed drug release. These will impact which polymer to be employed. Upon choosing the coating material of choice, modeling can also be employed to predict in vitro and in vivo correlation as enteric-coated products can have unpredictable in vivo PK profiles. Today, the trend is moving away from the traditional coating and towards new polymers, and with digitalization, there is a focus to start using data from laboratory experiments to be integrated with computational modeling, artificial intelligence, and machine learning to accurately predict key process parameters and film properties for high-quality products.