Quality by design concept not only demands machinery and process disigning for quality but also puts stress on designing chemistry of your product so as to build a far better quality product.
Quality by design concept requires that the quality of a pharmaceutical product should be inbuilt , and the designing of process , machinery , and formulation should yield the final product of best quality ,and its quality is not dependant on later inspection and controls , but it is getting produced as per you plan .
1.Planing the quality
2.Design the quality
Example 1
Design a machinery with auto sampler , which will provide you a samples of your final product automatically , from all level for all time intervals, which represents complete batch and process of a pharmaceutical dosage form , this provides better accuracy of control , than human inspections.
Quality by design concept requires that not only machinery but other aspects of your formulations are needed to be designed to get quality of final product.
This is a best idea Quality by design for pharmaceuticals manufactured.
You have the ability to design your formulation which should yield best quality final product.
You have to plan your quality of final product while you are designing your formulation.
Instead of putting stress on in process quality checking’s and inspections
This is what chemistry part of guidelines says.
Example 2
I will like to give an example how you can design a formulation to yield best quality.
Consider your final product is stable at PH 5.5, and a little fluctuation in final PH of your product gives you lot of problems .
While adjusting the final PH , your formula has given buffering agents quantities just sufficient to adjust the PH , and manufacturing person has assess to more than required quantity of buffering agent.
You have opportunity to design the quality here, by limiting the quantities of buffering agents.
Fix the quantity of the Buffering agent in the range of limit of +0.3 for final product
Now you have limited the access of manufacturing pharmacist to usage of buffering agent, he will use just sufficient quantity, and not quantity sufficient to adjust the PH of your final product.
This requires pilot as well as actual validations, and one it is set, your product will not have fluctuations in PH in wider range this will be always in the very small range of +0.3
This is true for other aspects of formulations too.
Setting limit on impurities in Raw material
Say a raw material is very critical for your pharmaceutical product.
You get this material which complies the pharmacopoeial limit for impurities.
But give lot of problems while in actual process.
You can design your limit of passing of this material test for impurities in the more strict range than that of pharmacopoeia.
You can develop your own method to analyze these impurities in the raw martial itself in better way so that you can ask your raw material manufacturer to make the material with your limit.
There are lots of tests which you can design to get best quality pharmaceutical product .
Guidelines on Pharmaceutical Manufacturing Pharma Quality Assurance Quality Management System 
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