Defects in tablet coating

Defects in tablet coating

1. FILM DEFECTS IN TABLET COATING 1 Raksha Laxman Mhetre Modern College of Pharmacy (for Ladies), Pune-412105

2. 1. Blistering It is a film detached from the tablets surface. Causes: High temperatures during the drying process, spraying stage or at the end of the coating process. Remedies: Use mild drying conditions, Ensure moderate temperatures at other stages of the coating process. 2

3. 2 . Blooming   Fading or dulling of a tablet colour after a prolonged period of storage at a high temperature. Causes: Use of high amount of plasticizer Using plasticizer with a low molecular weight Remedies: Decrease the concentration of plasticizer Increase the molecular weight of the plasticizer in the polymer 3

4. 3. Blushing It is a haziness or appearance of white specks in the film. Causes: High coating temperature may causes precipitation of polymer on tablet coating. Remedies: Decrease the drying temperature to avoid precipitation of polymer. 4

5. 4. Bridging It is coating fills in the letter or logo on the tablet. Causes: Improper formulation Poor logo design High coating viscosity Remedies: Reduce the viscosity of coating solution Increase the plasticizer content 5

6. 5. Capping The upper and lower crown of the tablet separates horizontally from the main body. Causes: Due to air entrapment Concave punches produce capping Remedies: Use of flat punches Use of hygroscopic substance 6

7. 6. Chipping It is the defect where film becomes chipped and dented at the edges of the tablet. Cause: Excessive attrition during coating process Remedy: Increase hardness of the film 7

8. 7. Cracking Small fine cracks observed on the upper and lower central surface of tablets. Cause: Due to the use of high molecular weight polymers Remedies: Use low molecular weight polymers Adjust the plasticizer & pigment concentration 8

9. 9 . Mottling Unequal distribution of colour on a tablet, with light or dark spots. Cause: Coloured drug whose colour differs from the colour of excipients Remedy: Use appropriate colour 9

10. 10. Orange peel effect It refers to a coating texture that resembles the surface of an orange. Cause: Inadequate spreading of coating solution before drying Remedy: Thinning the solution with additional solvent 10

11. 11. Picking Small amount of material from the tablet is sticking to and being removed off from the tablet surface by a punch face. Causes: Excessive moisture in granules Improper lubrication Remedies: Properly d ry the granules Increase the lubrication 11

12. 12. Pitting It is a defect whereby pits occur in the surface of tablet core. Cause: Temperature of tablet core is greater than melting point of the materials used in tablet formulation. Remedy: Control drying temperature 12

13. 13. Sticking Tablet material adhering to die wall. Cause: Improperly dried or improperly lubricated granules Remedies: Dry the granules properly Increase or change the lubricant 13

14. 14. Twinning Two tablets stick together and it is most common in capsule shape tablets. Cause: High spray rate causes over wetting tablets . Remedies: Reducing spray rate Increasing pan speed 14