After the compression of tablets, it is very important to evaluate the tablets. In this article, we will talk about the physical evaluation of a tablet after post-compression. This article will help you a lot by providing information about the post-compression evaluation as well as the finished product quality control tests for tablets.
Physical Evaluation of a Tablet
There are many specifications through which the Physical evaluation of a tablet after post-compression can be defined or characterized. These physical parameters of tablet post-compression include shape, size, diameter of tablets, thickness, hardness, weight, disintegration time, and dissolution of tablets.The shape and the diameter totally depend upon the punches and die selected for the tablet compression. Generally, the tablets' shape is discoid but can be round, oval, oblong, triangular, or cylindrical. The upper and lower surfaces of the tablets can be flat, round, concave, or convex.
If there is small dose is required then the tablet may be scored in halves or quadrants to make easy the breaking of the tablets.
To identify the source as well as the meaning of the tablets, the top, as well as bottom surfaces, can be engraved or imprinted with a letter or symbols. These characteristics including the color of the tablets make them identical.
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What are Various Tests for The Evaluation of Tablets?
1) Tablet Hardness or Crushing Strength:
The hardness of the tablet indicates the ability of the tablet to resist breakage under storage conditions, transportation, and mechanical shocks during handling.There is a hardness tester that is used to measure the hardness of the tablet.
A) Monsanto Hardness Tester:
It is a small and portable hardness tester which is manufactured by Monsanto. This instrument is used to measure the force which is required to break the tablet and the force generated by coil springs of the Monsanto hardness tester, which is measured in kilograms.
B) Strong-Cobb Hardness Tester:
This hardness tester is also used to measure the force which is required to break the tablet. The manually operated air pump produces the force in this tester. When the pressure increased, the plunger is forced against the tablet which is placed on an anvil and the breaking point is indicated on the dial.
C) Pfizer Hardness Tester:
This hardness tester is operated on the same principle as ordinary pliers. The force which is required to break the tablet is recorded on the dial and measured in pounds of force or kilograms.
Nowadays, electrically operated equipment is used to measure the hardness or crushing strength of the tablet.
The hardness or crushing strength of the tablet is measured by doing the adjustments in the tablet machine.
If the tablet is too hard, it will not disintegrate in the specific period as per the standards, and also will not be able to meet the dissolution specifications.
In the same way, if the tablet is too soft, it will not withstand handling during the processing like coating, packaging, and shipping as well.
2) Friability:
The friability is related to the hardness of tablets which is determined by using the Roche friabilator. This instrument is designed to evaluate the ability of the tablet to withstand friction or wear off in handling, packaging, and shipping.At least ten tablets are weighed and placed in the apparatus. Then the friabilator operated at 25 rpm (revolution per minute) for four minutes or run up to 100 revolutions. Then again the tablet weighed and the loss of weight shows the ability of the tablet to withstand this type of situation.
The % friability is then calculated by using the following equation.
% Friability = Initial weight (Wi) – Final weight (Wf) / Initial weight (Wi) × 100
% Friability of tablets less than 1% is considered acceptable.
3) Tablet Thickness:
The thickness of the tablet can vary due to pressure applied to the tablets as well as the tablet compression speed and also due to the differences in the density of the granulation.The thickness of the tablet is very important because if the tablet will be thicker than the given standards then the required number of tablets will not be filled in the given bottle size.
The thickness of the tablet is measured by the thickness gauge or caliper which measures the thickness of the tablets in millimeters. The thickness of the tablet, plus or minus (±) 5% is allowed, It is totally depending upon the SOP (standard operating procedures).
4) Weight Variation Test:
Whenever any tablet is prepared that contains a specific amount of the drug, the weight of the tablet is measured continuously which helps to ensure that the tablet contains the proper amount of the drug.To measure this ten or twenty tablets randomly selected from each batch means throughout the compression process and weight individually to check for variations in weight.
The batch passes the weight variation test if not more than two tablets are out of the percentage limit and if no tablets deviate more than two times the percent limit.
According to IP the Specifications of Weight Variation of Tablets
| Average weight of tablets (mg) | Maximum % deviation allowed |
|---|---|
| 80 or less | ± 10 |
| From 80 to 250 | ± 7.5 |
| More than 250 | ± 5 |
5) Disintegration Test (DT):
The disintegration test is used to measure a group of tablets to disintegrate into particles in the given conditions within the specified time frame.The time that a tablet takes to disintegrate is measured in an apparatus called disintegration apparatus.
Usually, in compressed, uncoated tablets the testing fluid is water with a temperature maintained at 37°C is used.
The USP (United States Pharmacopoeia) device which tests the disintegration contains 6 glass tubes that are 3 inches long, open at the top, and a 10-mesh screen attached at the bottom end of the basket assembly.
For testing the disintegration time, one tablet is placed in each tube, and the basket assembly is placed in a 1-liter beaker of water or simulated gastric fluid or simulated intestinal fluid, at a temperature of 37°C, in such a way so that the tablet remains 2.5 cm below the surface of the liquid to their upward movement and descend or sink not closer than 2.5 cm from the bottom of the beaker.
A motor-driven device is used to move the basket assembly that contains the tablet up and down through a distance of 5 to 6 cm at a frequency of 28 to 32 cycles per minute.
In this test, a perforated plastic disc is used that is placed on the top of the tablets and is useful for tablets that float.
As per the USP standards, a tablet must be disintegrated, and all particles must pass through the 10-mesh screen in the specified time. The residue remains must be a soft mass.
The disintegration time for invested tablets should be as low as 5 minutes but many tablets have a maximum disintegration time of 30 minutes and the disintegration time for enteric-coated tablets is 1 hour or more, specified in the monograph.
6) Dissolution Test:
The rate of dissolution is directly related to the bioavailability as well as the efficacy of the tablets. The dissolution test is performed to know whether a tablet releases its drug contents when put in the environment of the gastrointestinal tract or not is the main concern of manufacturers. For this reason, the in vitro dissolution study is performed and used as an indirect measurement of drug availability.The objective of in vitro dissolution test is to release almost 100% drug from the tablet and the rate of release of the drug should be uniform.
a) Basket Type:
In this apparatus, a single tablet is put in the small wired mesh basket that is connected to a variable-speed motor. The basket is dipped in the dissolution medium that contained a 100 ml flask.The cylindrical flask with the hemispherical bottom is maintained at 37°C ±0.5°C by a bath with constant temperature and the motor is adjusted to a specific speed and fluid samples are withdrawn at intervals to measure the amount of drug in the solution and fill the flask with the same fluid to maintain the sink condition.
b) Paddle Type:
This is also basket-type apparatus but the main difference is that basket is replaced with a paddle that is formed from a blade and a shaft is for stirring.By taking an example of any tablet the dissolution test starts with a medium of 900 mg of 0.1N HCL at a speed of 50 rpm for 20 minutes. The amount that is acceptable in 20 minutes should not be less than 80% of the specified amount of the drug.
I hope you like my article Physical Evaluation of a Tablet After Post-Compression. I give up the information about the In-process quality control test for tablets after compression. If you have any questions or queries related to the article then feel free to ask in the comment section.
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