Weight variation or uniformity of weight is a quality control test for dosage forms that are performed to ensure that each dosage contains the appropriate amount of drug.
A tablet is one of the most common oral solid dosage forms of pharmaceuticals for oral administration, containing powder compacts that include both active ingredients (API) and excipients. Excipients are used in formulation to achieve a specific fill weight in a dosage form, improve drug release behavior, protect, support, or enhance stability, patient acceptability, or bioavailability. Depending on the number of medicinal substances and the intended route of drug administration, they vary in weight, shape, size, thickness, hardness, dissolution, solubility, and other releasing properties.
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When compared to other types of dosage forms, tablets are the most popular among physicians, patients, and manufacturers because they offer a wide range of applications and, advantages as well as good physical and chemical stability and ease of swallowing. However, if a minute error arises throughout the manufacturing process, the entire batch may be discarded, which is a major disadvantage in its formation. Thus, evaluation of tablets is extremely significant to avoid any errors throughout the production of tablets. The different types of tablets such as compressed, multiple-compressed sustained action, chewable, sublingual, buccal, sugarcoated, film-coated enteric-coated and gelatin-coated tablet, etc. are formulated as per the requirement.
Quality control is the process by which a manufacturer measures actual quality performance, compares it to pharmacopeia standards (USP/IP/BP), and determines the causes of deviation from the standard in order to produce a consistently high-quality product.
What is a weight variation test?
Weight variation test is also known as uniformity of weight, it is the official quality control test which is performed to ensure that each tablet dosage form has the accurate amount of drug. The consistency of weight is a process test parameter that ensures uniformity of dose units as per the label claim. The test is conducted by weighing 20 tablets individually on an analytical balance, computing the average weight, and comparing the individual weights of the tablet to the average.
How do you perform a weight variation test?
If the statistical distribution of the weight of the tablet is considered normal then all tablets should fall within the prescribed range of established tablet weights. Throughout the manufacturing process, the average weight and variation of individual tablet weight from the average are calculated and controlled to ensure that the tablets contain the desired amount of drug and that there is no more than acceptable variation among tablets within a batch.
The test procedure for weight variation:
- Required apparatus and materials are tablets/caplets/capsules, electronic or analytical balance, and weighing boat, etc.
- As per the USP, weigh the randomly selected 20 tablets individually and calculate the average weight.
- If no more than two tablets exceed the % limit and no tablets differ by more than twice the percentage limit, the tablet passes the USP test.
How to calculate weight variation test for tablets?
The weight variation test is calculated using the formula, weight variation = (IW - AW)/AW X 100% Where, IW is individual weight, and AW is average weight.
The following table lists the USP, BP, and IP limits for tablet weight variation.
These standards are exempted for coated tablets, but they must pass the content uniformity test.
What are the factors that affect weight variation?
The weight variation of the tablet is mostly influenced factors by the machine speed, head pressure, compression machine, particle size distribution, and the flow properties of the powder, and degree of segregation, these are the common cause of weight variation throughout compression.
Commonly asked questions on the evaluation of tablets are as follows.
What is the advantage of the weight variation test?
The major advantage is that it is an official in-process test that ensures that each dose contains the proper amount of drug.
What are the tests quality control tests for dosage forms?
The different evaluation tests are uses such as appearance, size and shape, organoleptic properties, unique identification marking, hardness, weight variation, friability, content uniformity, disintegration, and dissolution these are the test for tablets are used as per the official/non-official standards.
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