Like we see defects in tablet compression, tablet coating is also associated with some defects. In this article, we will see the defects that are possible for coated tablets during the manufacturing process and most of the defects are due to the low technical skills of the operator. These defects must be minimized as tablet coating is done to improve the stability of the core tablets.

Defects associated with tablet coating

• Blistering
• Chipping
• Sticking & picking
• Twining
• Cratering
• Blooming
• color variation
• Incomplete coating of the core
• Surface erosion
• Discoloration
• Blushing
• Roughness or orange peel
• Color variation

Surface erosion – it is a coating defect that can occur when tablets fall during coating due to high friability or excessive pan speed or low spray rate of the coating process. The possible remedies include increase the spray rate, reducing the pan speed, making the tablets less brittle and increasing the film strength.

Color Variation – The problem occurs due to low coating, or improper mixing of coating solution and the remedies include proper mixing of coating solution, use of lake dyes and reformulating with different additives and plasticizers is the best way to prevent color variation.

Chipping means the film gets chipped at the edges and this occurs due to decrease in fluidizing air or speed of the coating pan and can be overcome by use of correct baffles for coating, loading adequate number of tablets in coating pan and optimum drying should be done.

Picking occurs, when tablets stick and separates apart and during this a part of coating layer is pulled off and this can be overcome by reducing the Spray rate and increasing the inlet air temperature.