tablet defects

• An ideal tablet should be free from any visual defect or functional defect.
• The advancements and innovations in tablet manufacture have not decreased the problems, often encountered in the production, instead have increased the problems, mainly because of the complexities of tablet presses; and/or the greater demands of quality.
• An industrial pharmacist usually encounters number of problems during manufacturing.
• Majority of visual defects are due to inadequate fines or inadequate moisture in the granules ready for compression or due to faulty machine setting.
• Functional defects are due to faulty formulation.
• Solving many of the manufacturing problems requires an in-depth knowledge of granulation processing and tablet presses, and is acquired only through an exhaustive study and a rich experience.
• The imperfections found in tablets are known as 'Visual Defects' and they are either related to imperfections in any one or more of the factors.
• Tablet processing problems can be due to the problem in the formulation or in the compression equipment, or both of them.
• The defects related to Tabletting Process are: Capping, Lamination, and Cracking.
• The defects related to Excipient are: Chipping, Sticking, Picking, and Binding.
• The defect related to more than one factor is known as Mottling.
• Increase viscosity of coating solution to decrease spray application rate.
• Picking is a defect where isolated areas of film are pulled away from the surface when the tablet sticks together and then break apart.
• The causes of Picking include inefficient drying and higher rate of application of coating solution.
• The remedy for Picking is to use optimum and efficient drying conditions or increase the inlet air temperature.
• Pitting is a defect where pits occur in the surface of a tablet core without any visible disruption of the film coating.
• The cause of Pitting is inappropriate drying (inlet air) temperature.
• The remedy for Pitting is to dispense with preheating procedures at the initiation of coating and modify the drying (inlet air) temperature such that the temperature of the tablet core is not greater than the melting point of the batch of additives used.
• Blushing is a defect best described as whitish specks or haziness in the film.
• The causes of Blushing include high coating temperature and use of sorbitol in formulation which causes largest fall in the thermal gelation temperature of the Hydroxy Propyl Cellulose, Hydroxy Propyl Methyl Cellulose, Methyl Cellulose and Cellulose ethers.
• The remedy for Blushing is to decrease the drying air temperature and avoid use of sorbitol with Hydroxy Propyl Cellulose, Hydroxy Propyl Methyl Cellulose, Methyl Cellulose and Cellulose ethers.
• Colour variation is a defect which involves variation in colour of the film.
• The causes of Colour Variation include improper mixing, uneven spray pattern, insufficient coating, migration of soluble dyes-plasticizers and other additives during drying.
• Infilling is a defect that renders the intagliations indistinctness.
• The causes of Infilling include bubble or foam formation because of air spraying of a polymer solution.
• The defect related to Machine is known as Double Impression.
• Orange peel/roughness is a surface defect resulting in the film being rough and nonglossy, appearing similar to that of an orange.
• The causes of orange peel/roughness include inadequate spreading of the coating solution before drying.
• Cracking/splitting is a defect in which the film either cracks across the crown of the tablet (cracking) or splits around the edges of the tablet (splitting), due to internal stress in the film exceeding tensile strength of the film.
• The causes of cracking/splitting include use of higher molecular weight polymers or polymeric blends, use of lower molecular weight polymers or polymeric blends, adjustment of plasticizer type and concentration, and improper application of the solution.
• Bridging occurs when the coating fills in the lettering or logo on the tablet and is typically caused by improper application of the solution, poor design of the tablet embossing, high coating viscosity, high percentage of solids in the solution, or improper atomization pressure.
• During drying, the film may shrink and pull away from the sharp corners of an intaglio or bisect, resulting in a bridging of the surface.
• Increasing the plasticizer content or changing the plasticizer can decrease the incidence of bridging.
• Tablets are the most common and frequently used among oral dosage forms due to its relative low cost and ease of administration.
• Defects in the tablets can arise during manufacturing processes, storage or transport.
• These visual defects can reduce the acceptability by the users and effectiveness of the product.
• The focus of this discussion was to establish ways to resolve common defects at the tablet press, and to identify the root cause of each and finally resolve the defect before it reaches the tablet press.
• A coloured drug is used along with colourless or white-coloured excipients.
• A dye migrates to the surface of granulation while drying.
• Improperly mixed dye, especially during 'Direct Compression', can cause problems.