Tablet coating defects

While performing the operation of Tablet coating various problems arises due to Human mistake which must be avoided by person involved in operation.

Black spots problem is observed in some organisations sometimes it has led to destruction of whole batch also. We must know the root cause to avoid the problem.

1. Black spots could come from machine due to improper cleaning.
2. Black Particles could be present in suspension of coating solution.
3. Excess of Titanium dioxide in coating solution will lead to black spots because density of Titanium dioxide is high than SS316 (Material of construction of coating pan). So, When the tablet containing high concentration of  Titanium dioxide is rubbed over coating pan the black spots will appear on tablet to avoid the problem. firstly, It should be avoided to use high concentration of Titanium dioxide in coating solution. If this can’t be avoided the coating pan must be precoated with solution before loading the tablets in pan and high RPM and excessive loading of tablets must be avoided on pan.

• Pressure of exhaust air should be larger than inlet air inefficiency to achieve this will cause Back-flow of solution which jams the tips of spray guns.
• High pan RPM is an human error which could lead to problems in batch. The Edges of tablets could rupture, Non uniform coating and problems like Twinning could appear in batch .
• Low spray rate is another problem which could lead to Non uniform weight gain.
• High distance of nozzle to bed If distance is more the solution will dry before it reaches the tablet bed due to exhaust air temperature and sufficient weight gain will not be there.
• Low nozzle to bed distance will lead to overwetted tablets.
• Low Bed/Exhaust temperature will lead to non uniform drying of tablet bed causing problems like Twinning.
• Nozzle to nozzle distance also plays critical role during coating less distance leads to overlapping of spray .