Coating Flashcards
List some reasons for coating of solid dosage forms.
Stability and protection
Masking unpleasant taste/odour
Ease of swallowing
Identification
Modification of drug release
List 5 types of coating
Film
Sugar
Press
Hot melt
Electrostatic
Briefly describe film coating
Depositing a thin polymer film onto surface of dosage form
List 4 component in film coating formulation
Polymer
Plasticizer
Colorant/ opacifier
Vehicles
Describe the role of colorants and opacifiers
Aesthetic appeal
Identification
Describe the role of plasticizers
Film flexibility
Reduce cracking/ brittleness
Improve adhesion film to surface of dosage form
Describe the mechanisms of film formation in solutions
- Components dissolved
- Rapid evaporation of solvent
- Increase in conc of polymer and contraction in volume of coating liquid on surface.
- Polymer molecules become immobile
- Final loss of solvent due to diffusion of residual solvent
Describe the mechanisms of film formation in aqueous dispersions
- Particles dispersed in solvent
- Droplets adhere to substrate surface and lose water due to drying
- Particles form contacts and capillary forces initiate coalescence
- Residual water escapes slowly by diffusion through capillary channels
- Complete coalescence due to viscous flow, enhanced by drying
List factors affecting formation of droplets in the coater device
Spray nozzle - pneumatic/ hydraulic
Heat
Movement of the cores
Exhaust
State 2 types of coaters
Perforated pan
Fluid bed coater
Describe the sugar coating process
Successive application of sucrose solution in tablets
Sealing to protect tablet from over wetting
Sub-coating to form shape of tablets
Smoothing
Colouring
Polishing
State 3 common problems in sugar coating
Visual defects
Sugar inversions
Sticking of coated tablets
