Several defects can occur during the coating process, affecting the tablet's appearance, performance, and patient acceptability.
A) Common Coating Defects
Capping: Partial or complete separation of the coating from the tablet.
Peeling: Large sections of coating detach, exposing the tablet.
Cracking: Visible cracks in the coating film, potentially affecting integrity.
Streaking: Uneven color distribution, resulting in visible streaks.
Mottling: Irregular coloration or blotches due to inconsistent spray or drying.
Pick-Up: Excess coating material adheres to non-tablet surfaces within the equipment.
Weight Variation: Inconsistent coating thickness leads to weight discrepancies.
Color Inconsistency: Variations in color intensity or hue across batches.
B) Causes of Coating Defects
Inadequate Mixing: Poor distribution of coating solution.
Incorrect Solvent Evaporation: Excess moisture or incomplete drying.
Temperature Fluctuations: Overheating or insufficient heating affecting polymer properties.
High Humidity: Moisture affecting the drying process and coating adhesion.
Improper Equipment Parameters: Incorrect spray rates, air flow, or rotation speed.
Tablet Surface Issues: Rough or uneven tablet surfaces hinder uniform coating.
Excessive Coating Thickness: Leads to cracking or capping.