Tablet Coating Flashcards
Describe polymer film (IR) coating
Wet process
Describe sugar coating
Wet process
Traditional + cheap
Describe compression coating
Dry process
Describe the type of film coating for immediate release
Side chain hydrophilic
Soluble in stomach = ionise at low pH
Describe the type of film coating for delayed release
Insoluble in stomach = acidic
Dissolve in small intestine
Describe the type of film coating for extended release
Insoluble in H2O = hydrophobic
Describe film coating method
Atomised coating formulation sprayed on to tablet
Tablets coated in a coating drum
Particles coated in fluidised bed coater = formulate sprayed below suspended particles
What are the advantages of film coating?
Protect dosage form
Range of coating excipients
Single-step process
Thin coatings = minimum weight
Retains tablet shape + surface features
What are the disadvantages of film coating?
High cost + footprint
Use of organic solvents may pose potential hazards
What are the advantages of sugar coating?
Inexpensive
Safe/accepted raw materials
What are the disadvantages of sugar coating?
Significant weight gain
Water-soluble coat = IR only
Multi-step process
Alters shape of tablets
Embossing not possible
Describe the sugar coating steps
Sealing = waterproof core = layers of polymer
Subcoating = apply 3-5 layers of sucrose syrup
Smoothing = apply 5-10 layers of sucrose syrup
Colouring = apply several coats of thin syrup with colourant
Polishing = apply wax for glossy appearance
Printing = print text or symbols in edible ink
Describe bridging (film-coating defect)
Film coating lost indented markings
Caused by film shrinkage upon drying
Describe orange peel effect (film-coating defect)
Uneven spreading
Caused by incorrect atomisation or spray rate
Describe core erosion (film-coating defect)
Disfigurement of tablet surface
Cause by over-exposure to formulation
Describe cracking (film-coating defect)
Fissure in film coating
Caused by insufficient mechanical strength, insufficient plasticiser + thermal expansion of tablet
Describe peeling (film-coating defect)
Film coating lifts off tablet surface
Caused by insufficient adhesion between film + tablet
Describe twinning (film-coating defect)
Tablets stick together along the edges
Caused by coating formulation that is too viscous or inefficient drying
How do you reduce twinning?
Circular/oval tablets reduce it
What type of process is compression coating?
Dry process
What is the problem with compression coating?
Expensive + complex
How can delayed drug release be achieved via compression coating?
Change the ratio of sodium alginate
Change coating thickness
What happens if you increase the amount of sodium alginate?
Longer the delay
What happens if you increase thickness of the coating?
Longer the delay
