Chrominfo: Difference between content uniformity and assay

The major difference between content uniformity and assay is that content uniformity is a quality control test in which the individual evaluation units are performed, while assay is a test in which numerous units are performed at the same time. Moreover, the evaluation process of uniformity of content tests is the same for all units.

Dosage forms are pharmaceutical products that deliver active pharmaceutical ingredients (API) to a particular part of the body in order to cure diseases. The physical forms of the dosage forms include solid, semisolid, liquid, and gaseous, while the routes of drug administration include oral, parenteral (injection), inhalation, sublingual, buccal, topical, and among others. Examples of dosage forms include tablets, capsules, caplets, granules, powders, pastes, aerosols, creams, linctus, gels, colloids, elixirs, suspensions, liniments, drops, emulsions, lotions, syrups, liquids, and solutions.

Table of Contents

Content uniformity test
Assay
Difference between content uniformity and assay
Similarities between assay and content uniformity
Why do we perform a content uniformity test

Pharmaceuticals should be in the form of safe, clinically effective formulations that are administered consistently and predictably. Therefore they should be evaluated by quality control tests which are mentioned in the pharmacopeias (USP/BP/IP) which also mentions their standard limits. The evaluation test consists of appearance, organoleptic properties, weight variation, hardness, content uniformity, friability, disintegration, and dissolution test. These tests must be done throughout the manufacturing and validated after each batch is completed in order for the product to meet quality standards (official or unofficial).

The content uniformity test and the assay are both are the quality control test used to determine whether a dosage form (tablet/capsule) batch is acceptable. These two tests are not independent, and their acceptance criteria are inconsistent.

Content uniformity test:

It is used to verify that the drug substance is evenly distributed in a production batch. This is done by determining the amount of the active ingredient in each of the dosage units. It gives criteria for the individual active ingredients measured, with no requirements for average and standard deviation. In which the number of dose units taken at random (10), and uniformity were accepted if individual values were found to be in the range of 85–115% of the calculated average.

Assay:

The purpose of the assay test is to verify that the average active content of a sample batch is close to its label claim. The assay limits for medicines are defined in the pharmacopeia monographs. The maximum allowable deviation from the label claim upon release should not exceed ± 5%.

Difference between content uniformity and assay:

Uniformity of content is used to ensures that each dosage form contains the same amount of drug or medication, whereas assay is used as an analytical process to qualitatively assess or quantitatively determine the presence, quantity, or functional activity of a sample. This is another major difference between assay and content uniformity.
Content uniformity is a type of qualitative test, whereas an assay can be both qualitative and quantitative.
In a content uniformity test, each unit is evaluated individually, whereas, in the assay, testing is done by combining the content of numerous units (tablets/capsules).
A content uniformity test is used to assess the uniformity of active ingredients, whereas an assay is used to characterize the main functional component of a sample.
In content uniformity, the pharmaceutical drugs are used as a sample, whereas in assay the pharmaceutical drugs, protein, DNA, RNA, antibodies, carbohydrates, and metal ions, etc. are used as a sample.

Similarities between assay and content uniformity:

Assay and content uniformity is the quality control test (analytical tests) which is used to determine the quality of a pharmaceutical product. They both are used the same procedure and their samples are the same (drug).