#FilmCoated Tablets – Film-Coating Defects Flaw Cause Remedy
Wrinkling or blistering
Flaw: Film detaches from tablet surface, causing blister that can burst to form wrinkles.
Cause: Gases forming on tablet surface during coating; exacerbated by poor adhesion of film to tablet surface.
Remedy: Reduce drying air temperature.
Picking
Flaw: Areas of tablet surface are not covered by film coat.
Cause: Overwet tablets stick together and pull film off surface as they move apart.
Remedy: Decrease spraying rate. Increase drying temperature.
Pitting
Flaw: Holes appear on tablet surface.
Melting of lubricant on tablet surface. Most common with stearic acid.
Remedy: Decrease coating temperature to below melting point of lubricant. Substitute lubricant
Blooming
Flaw: Dulling of surface, normally after prolonged storage.
Migration of low-molecularweight components of film to tablet surface.
Remedy: Decrease temperature and length of drying process. Increase molecular weight of plasticizer.
Mottling
Flaw: Uneven color distribution in film.
Inadequate pigment dispersion. Color migration, a problem with dyes and lakes rather than pigments.
Remedy: Alter suspension preparation to ensure pigment aggregates are dispersed. Replace dyes with pigments.
Orange peel
Flaw: Film surface has a rough finish resembling orange peel. Film-coat droplets are too dry or too viscous to spread on tablet surface.
Remedy: Reduce solids content of coating suspension. Reduce drying temperature. Reduce viscosity of polymer.
Bridging
Flaw: Film forms a bridge over intagliations, leaving them indistinct. High internal stresses in film relieved by pulling the film off the Surface of the intagliation.
Remedy: Increase adhesion of coat to tablet by changing core formulation. Add plasticizer or increase plasticizer concentration. Alter geometry of intagliations.
Cracking, splitting, peeling
Flaw: The film cracks on the crown of the surface or splits on the tablet edge. Can be differentiated from picking by presence of loose film around the flaw.
High stresses in the film that cannot be relieved due to the strong Adhesion of the film to the tablet surface.
Remedy: Increase plasticizer concentration. Use stronger polymer.