Content uniformity and blend uniformity are the two most important tests which are performed for solid dosage forms like tablets, capsules and sachets. Many professionals are not aware of the key differences and basic information about blend uniformity and content uniformity. In this article, you will learn all about blend uniformity and content uniformity.
Blend uniformity
Blend uniformity is also known as BU, and it is the in-process test which is performed for the powder/granules blend after final mixing to ensure that the mixing of the powder/granules blend is uniform and homogeneous.
Stage
Blend uniformity is performed for the powder or granules after the final blending step, meaning when all the excipients and APIs are mixed together, we take samples for blend uniformity. In simple words, BU is performed before compression, filling of capsules or sachets.
Purpose
Blend uniformity test gives us assurance that our mixing process was accurate and there is no segregation.
What To Check
During the blend uniformity test, we check that all APIs are equally and uniformly distributed in the final blend.
Sampling
For blend uniformity, the sampling plays an important role, so we take samples from the blender at different locations, and each sample must ensure the uniform distribution of API.
Factors Affecting Blend Uniformity
The following factors may affect blend uniformity
Blending Time
Blender Speed
Blender Occupancy
Segregation
Blending Time
If blending time is kept short, it will result in non-uniformity of the blend, so the optimal blending time is locked during validation to ensure uniform mixing.
Blender Speed
If the load in the blender is high but the mixing speed is too slow, it will not ensure uniform mixing, so blend uniformity will be affected.
Blender Occupancy
About 20 to 30% head space must be available in the blender during the mixing process to ensure uniformity, so if the blender is overloaded or underloaded, it will result in non-uniform distribution of API.
Segregation
Segregation may occur due to overmixing or variation in particle size of the mixed blend; this segregation results in disturbance of blend uniformity.
Content uniformity
Content uniformity is also known as CU, and it is the in-process test which is performed for the tablets, capsules or sachet after compression or filling, respectively, to ensure that each dose contains the claimed amount of APIs e.g 90 to 110%
Stage
CU is performed after compression and filling of capsules or sachet.
Purpose
The purpose of CU is to ensure dose uniformity.
What to Check?
CU is performed to check that each tablet and capsule/sachet contains the claimed amount of active pharmaceutical ingredient to perform its desired pharmacological action.
Samples
Different samples are taken at different time intervals during tablet compression, capsule filling or sachet filling.
Relationship between BU and CU
There is a direct relationship between blend uniformity and content uniformity, meaning that if blend uniformity is disturbed, the content uniformity results will also be affected.
The content uniformity results may also be affected even if blend uniformity results are acceptable, and this variation in CU results may occur due to segregation issues during compression or filling stages.
Factors Affecting Content Uniformity
The following factors may affect content uniformity
Poor BU
Poor Flow
Segregation during feeding
Poor BU
If blend uniformity is compromised, the content uniformity will also be affected.
Poor Flow
Poor flow of powder or granules from the hopper to the feeder or filling cavities may affect CU due to segregation.
Segregation during feeding
Content uniformity is also affected during the feeding process due to segregation resulting from non availability of force feeders.
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