Pre-mixing is one of the most important steps of the granulation and dry mixing process which are used for the manufacturing of tablets, capsules and dry powder suspension. In this article, we will learn what is the pre-mixing process, why we need the pre-mixing process and what is the order of mixing and which equipment are used for pre pre-mixing step.
What is the pre-mixing process?
As the name indicates pre-mixing is the mixing process which is performed before the kneading or wetting step of wet granulation or slugging step of the dry granulation process. The word pre-mixing is used to differentiate the two mixing types during the granulation process. In the granulation process basically mixing is performed in two stages one is before the kneading or slugging process and the second one is performed after the dry sieving of the granules or screening of the slugs which is known as final mixing or final blending.
So premixing is the process which is performed at the initial stage of the wet or dry granulation.
Purpose of the premixing process
The purpose of the premixing process is to ensure that all the excipients and API which are used for the kneading or slugging step are mixed uniformly. In simple words, pre-mixing process shows that the content uniformity of the blend ready for granulation is uniform and each dose will contain a uniform quantity of the excipients and active pharmaceutical ingredients.
As we discussed previously the pre-mixing step is performed before the kneading or slugging process so if we do not perform the premixing process mean if you do not uniformly mix our excipients or API properly before the kneading stage then there will be no uniformity of the active pharmaceutical ingredient and excipients in the final dose.
So we perform the pre-mixing step to ensure the uniformity of the materials for which we are going to perform the wet granulation process or dry granulation process.
How to perform
Different types of excipients and active pharmaceutical ingredients are used in different formulations and the order of mixing or the ingredients which are used during the premixing step vary depending upon the formulation.
For example, for some formulations, we may only mix the diluent and disintegrants in the pre-mixing step. For other formulation, we may mix diluent, disintegrant and colourant and for some other formulation we may mix the active pharmaceutical ingredient, diluent, and disintegrant or we can mix active pharmaceutical ingredient, diluent, disintegrant and colourant.It all depends on the formulation of which type of materials are to be mixed but the purpose is the same to get the uniformity before kneading or slugging process.
Equipment used for pre-mixing
Any type of low-shear or high-shear mixing equipment can be used for pre-mixing step during tablet, capsule or dry powder suspension manufacturing. Most commonly used are the double cone blender, rapid mixing granulator, ribbon mixer or plough mixer.
If we use a double cone blender then after pre mixing we transfer the mixed blend to the granulating equipment and if we use a plough mixer, ribbon mixer or rapid mixing granulator then the kneading step is performed in the same equipment after pre mixing.
Conclusion
Pre-mixing is the step performed during the wet or dry granulation process to ensure the uniformity of the excipients and active pharmaceutical ingredients. Pre-mixing is done prior to the wetting step or slugging process. The order of mixing and type of materials used for pre-mixing vary depending on the product and formulation. Without pre mixing step the content uniformity will be compromised.
Also Read