A film coating is a thin polymer-based coating that is usually sprayed onto solid pharmaceutical dosage forms such as tablets, capsules, pills or granules. Thin film coating affects its appearance and pharmacokinetics, making it an important process in the manufacture of final drug products.
Film coatings are a common form of drug coating, often used for oral medications. Motivations for applying film coatings to dosage forms include cosmetic considerations (color, gloss, and branding), improving shelf life by providing a protective barrier between the drug and the surrounding environment, and making dosage forms easier to swallow. These types of thin film coatings are known as non-functional thin film coatings. They can also be used to delay or increase the delivery and absorption of a drug, or to delay release and absorption until the drug passes through the stomach. These types of thin film coatings are known as functional thin film coatings.
Conventional methods for applying film coatings to oral dosage forms include a spraying stage and a drying stage. The spray stage involves the application of polymers, plasticizers, colorants, opacifiers, solvents and carriers to the core layer of the oral dosage form. Once applied, the oral dosage form is dried by passing hot air over the dosage form, which usually also removes the solvent. The end result is a thin film coating with the desired plasticizer, color, opacifier and carrier.
non-functional coating
Non-functional film coatings involve changes to the aesthetics of oral dosage forms. Such changes can affect the oral dosage form's appearance, sensory properties, swallowing characteristics, and provide protection against harsh environmental conditions that may damage the active pharmaceutical ingredient. These changes were made to improve the compliance and efficacy of the oral dosage form. For example, the appearance can be changed by changing the color of the drug to make the product more attractive. Changing swallowing characteristics can make swallowing easier for those who have difficulty swallowing. Finally, adding a protective film against harsh environmental conditions such as humidity, oxidation or light can extend the shelf life of the final product.
functional coating
Functional thin-film coatings offer the same properties as non-functional thin-film coatings, but with additional properties that affect drug release. These changes alter the region of the gastrointestinal tract where the final drug product is released. See Extended Release Dosage and Enteric Coating.
Organic Solvent Based Coatings
Organic solvents used in film coatings are often used to incorporate protective coatings into oral dosage forms, which help to extend the shelf life of the final drug product. This type of thin film coating can be hazardous due to its potential toxicity in the final product and flammability during the thin film coating process. Therefore, proper safety measures and ventilation are required when applying the film.
water-based paint
Water-based thin film coating is currently the most commonly used thin film coating method. This type of thin film coating uses water instead of organic solvents to aid in the thin film coating process. The result is a safer way of coating thin films because it avoids the toxic and flammable properties of organic solvents. Water-based film coatings require the use of water-insoluble polymer blends with the addition of plasticizers. Despite their widespread popularity, aqueous film coatings are more time-consuming than organic solvent-based coatings due to the increased time required for water to evaporate completely.
Solvent Free Coating
Due to the benefit of not requiring a drying stage, solvent-free film coatings are often used to coat heat-sensitive pharmaceuticals. The end result of this thin film coating is an inert thin film coating that does not react with the active pharmaceutical ingredient. Some methods of producing solvent-free thin film coatings include injection molding coating, hot melt coating, and spray condensation. Each method has its own advantages and disadvantages, but their common theme is that very precise conditions are required to satisfactorily apply film coatings to oral dosage forms. Therefore, it is an inefficient type of thin-film coating, leading to its lack of widespread use.
杨光; 葛志宏 - 《表面技术》