Importance of Mixing Time in Blend Uniformity

Importance of mixing time and effects of extended mixing time on blend uniformity and pharmaceutical product quality.

In pharmaceutical tablet manufacturing process more than one ingredients are mixed during blending in a dry powder blender. It always remains in one's mind that what will happen if we increase the mixing time than specified in the batch manufacturing records.

Mixing time during blending is an important factor that can affect the product quality. An increased mixing time can cause the segregation or de-mixing of the bland ingredients.

Importance of mixing time during blendingPowders have a tendency of segregation during mixing that can cause unequal distribution of pharmaceutical ingredients in dosage units. Following are possible reasons those are responsible for the de-mixing of the powders.

1. Particle Size: Difference in particle size of the blend ingredients may help to segregate the material.

2. The density of Materials: A considerable difference in density of materials being mixed may cause the segregation of the material having a higher density.

3. Interaction of Materials: Interaction between drug and the excipients may cause the de-mixing of the ingredients.

Above three factors work during the blending when vibration occurs. Due to vibration smaller particles of material moves under the bigger particles. This causes the separation of the bigger and smaller particles in the same material. During the extended mixing time, the material having the higher density moves towards the bottom of the blender or mixer. It may also cause the separation of different blend ingredients based on their density and shows the importance of mixing time.

Different particles of materials have interaction between them and it can be increased during the blending. Particles of two materials having more interaction may segregate causing the material non-uniformity in the blend.

Therefore, blending of the dry powders for solid dosage forms must be done carefully. The validation of the mixing time is very important and it should be followed strictly during the manufacturing process.