Film coating is generally referred to as a process by which a thin, continuous, solid polymer layer is applied to the surface of a dosage form (typically tablets, capsules, and multiparticulates). The purpose of film coating includes esthetic enhancement, increased shelf life, taste masking, moderating the release profile of active pharmaceutical ingredient (API), trade-marking, and protection of intellectual property.
The thickness of the film is generally less than 100 μm. The composition of the film may include a mixture of excipients (polymers, plasticizers, colorants) as well as an API.
Film coatings avoid the need for the subcoating and smoothing operations needed for sugar coating. Similar coating pans that are used for sugar coating are used for film coating.
This article focuses on advantages and disadvantages of film coating.
1. The film process is simpler and, therefore, easier to automate
2. Enhances the elegance and glossy appearance of coated tablets.
3. Minimal weight increase (typically 2–3% of tablet core weight) as opposed to more than 50% with sugarcoating.
4. Increased ﬂexibility in formulations as a result of the availability of a wide range of coating materials and systems.
5. Moisture involvement can be avoided (if absolutely necessary) by using nonaqueous solvents.
6. Significant reduction in processing times with increased process efficiency and output.
7. Distinctive identification of tablet markings are easily obtainable.
8. Improves mechanical integrity and resistance to destruction by abrasion during transportation.
9. Ability to be applied to a wide range of pharmaceutical products (e.g., tablets, capsules, granules, nonpareils, powders, drug crystals).
1. Possible explosion as a result of the flammability of some of the organic solvents used as vehicles for the film-forming polymers.
2. Some of the solvents used in film coating processes are toxic and could constitute health hazard to the formulation scientist.
3. Some of the solvents and polymers used in film coating are relatively expensive.