Coating adds weight to every tablet, so comparing the weight of coated tablets with the weight of core tablets would show an apparent gain that hides real tablet loss. Coating reconciliation therefore counts tablets. The theoretical count is the number of core tablets loaded, and the actual count is the coated weight divided by the average coated tablet weight.
The calculator gives both counts and the percentage yield.
96.0 kg of core tablets (400 mg each) are coated. The coated tablets weigh 98.0 kg and the average coated tablet weighs 412 mg, a gain of 3%.
A direct weight comparison would show 98.0 against 96.0 kg, an apparent 102% yield, which is misleading.
Common causes of tablet loss are pan wall build-up, tablets chipped or broken in the pan, fines and fragments carried out with the exhaust air, and tablets rejected at appearance inspection. If the loss is high, check the core hardness and friability first, since weak cores break in the pan, then check pan speed and spray settings.
Check that the same balance and the same unit were used for the core and the coated weights, and that the average coated weight was measured on a representative sample. Then examine the pan after discharge for build-up and broken tablets, and weigh the dust and fragments collected in the exhaust system. Rejects from the inspection step should be counted and recorded as tablets, not as weight. If the loss is concentrated in broken tablets, review the core friability and hardness records for the same batch, because weak cores are a common cause of coating loss.
Record the core tablet weight and the number of core tablets or the core weight loaded at the start of coating, and record the coated weight at discharge on the same balance or on a balance of the same class. The average coated tablet weight should come from a sample taken after the pan has been unloaded and mixed, because tablets at the pan wall and tablets at the centre of the bed do not always carry the same gain. Keep the units consistent throughout, and state whether the weights are in kilograms or grams before the tablet counts are calculated. When the result is reviewed, the reviewer should be able to repeat the three steps of the arithmetic from the recorded numbers alone.
The checks on this page relate to the documents below. Standards are revised from time to time, so confirm the current edition and follow your own approved procedures.
Coating adds weight to each tablet. A direct weight comparison would show an apparent gain that hides real tablet loss.
Pan wall build-up, fines and chipped fragments carried out with exhaust air, and tablets rejected during inspection.
It depends on the product and the core quality. Use the limit in your batch record.
Related tools and guides: Coating Pan Loading · Tablet Coating Defects · Batch Reconciliation Explained · Coating Material Calculator · Coating Weight Gain Troubleshooting · Blister Reconciliation
By Sajjad Ahmad. For reference and education only; verify limits against your SOPs and the current pharmacopoeia. See the methodology.