Coating

Question 1

List some reasons for coating of solid dosage forms.

Answer 1

Stability and protection
Masking unpleasant taste/odour
Ease of swallowing
Identification
Modification of drug release

Question 2

List 5 types of coating

Answer 2

Film
Sugar
Press
Hot melt
Electrostatic

Question 3

Briefly describe film coating

Answer 3

Depositing a thin polymer film onto surface of dosage form

Question 4

List 4 component in film coating formulation

Answer 4

Polymer
Plasticizer
Colorant/ opacifier
Vehicles

Question 5

Describe the role of colorants and opacifiers

Answer 5

Aesthetic appeal
Identification

Question 6

Describe the role of plasticizers

Answer 6

Film flexibility
Reduce cracking/ brittleness
Improve adhesion film to surface of dosage form

Question 7

Describe the mechanisms of film formation in solutions

Answer 7

• 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

Question 8

Describe the mechanisms of film formation in aqueous dispersions

Answer 8

• 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

Question 9

List factors affecting formation of droplets in the coater device

Answer 9

Spray nozzle - pneumatic/ hydraulic
Heat
Movement of the cores
Exhaust

Question 10

State 2 types of coaters

Answer 10

Perforated pan
Fluid bed coater

Question 11

Describe the sugar coating process

Answer 11

Successive application of sucrose solution in tablets
Sealing to protect tablet from over wetting
Sub-coating to form shape of tablets
Smoothing
Colouring
Polishing

Question 12

State 3 common problems in sugar coating

Answer 12

Visual defects
Sugar inversions
Sticking of coated tablets