Tablet evaluation test

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Nahla Barakat, PhDKing Saud UniversityDept. of Pharmaceutics1431/1432

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The quantitative evaluation and assessment of a tablet‘s chemical, physical and bioavailability properties are important in the design of tablets and to monitor product quality.

These properties are important since chemical breakdown or interactions between tablet components may alter the physical tablet properties, and greatly affect the bioavailability of the tablet system.

There are various standards that have been set in the various pharmacopoeias regarding the quality of pharmaceutical tablets.

These include the diameter, size, shape, thickness, weight, hardness, disintegration and dissolution characters.

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General Appearance

The general appearance of a tablet, its identity and general elegance is essential for consumer acceptance, for control of lot-to-lot uniformity and tablet-to-tablet uniformity.

The control of general appearance involves the measurement of size, shape, color, presence or absence of odor, taste etc.

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Organoleptic properties Color is a vital means of identification for many pharmaceutical tablets and is also

usually important for consumer acceptance. The color of the product must be uniform within a single tablet, from tablet to tablet

and from lot to lot. Reflectance spectrophotometry, tristimulus colorimetric measurements and micro

reflectance photometer have been used to measure color uniformity and gloss on a tablet surface .

Odor may also be important for consumer acceptance of tablets and can provide an indication of the quality of tablets as the presence of an odor in a batch of tablets could indicate a stability problem, such as the characteristic odor of acetic acid in degrading aspirin tablets.

Taste is also important for consumer acceptance of certain tablets (e.g. chewable tablets) and many companies utilize taste panels to judge the preference of different flavors and flavor levels in the development of a product.

Taste preference is however subjective and the control of taste in the production of chewable tablets is usually based on the presence or absence of a specified taste.

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Size & ShapeIt can be dimensionally described & controlled.

The thickness of a tablet is only variables. Tablet thickness can be measured by

micrometer or by other device. Tablet thickness should be controlled within

a ± 5% variation of standard value.

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Weight Variation test (U.S.P.) Take 20 tablet and weighed individually.

Calculate average weight and compare the individual tablet weight to the average.

The tablet pass the U.S.P. test if no more that 2 tablets are outside the percentage limit and if no tablet differs by more than 2 times the percentage limit.

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Average weight Percent difference

  130mg or less

10 More than 130mg through 324mg

7.5

More than 324mg 5

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The content uniformity test is used to ensure that every tablet contains the amount of

drug substance intended with little variation among tablets within a batch.

the content uniformity test has been included in the monographs of all coated and uncoated tablets and all capsules intended for oral administration where the range of size of the dosage form available include 50mg or smaller sizes.

Tablet monographs with a content uniformity requirement do not have weight variation requirements.

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Content Uniformity Test: Randomly select 30 tablets. Ten of these assayed individually. The Tablet pass the test if 9 of the 10 tablets must contain

not less than 85% and not more than 115% of the labeled drug content and the 10th tablet may not contain less than 75% and more than 125% of the labeled content.

If these conditions are not met, remaining 20 tablet assayed individually and none may fall out side of the 85 to 115% range.

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Hardness (Fracture-resistance test): Tablets require a certain amount of strength or hardness.

Why?1. Withstand mechanical shocks of handling in

manufacture, packaging and shipping.2. Withstand reasonable abuse when in the hands of the consumer.  3. The relationship of hardness to tablet disintegration, dissolution .

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Tablet Hardness: the force required to break a tablet along its diameter by applying compression loading.

  Test Description:A tablet is placed between two anvils, force is applied to

the anvils, & the crushing strength that just causes the tablet to break is recorded (in kg).

Hence, Hardness is thus sometimes termed the tablet crushing strength.

    Tablet hardness should be between 5 – 8 kg

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Hardness Variation: It depends on: - compression force, - concentration and type of binding agent

If the tablet initially is too hard, it may not disintegrate

in the requisite period of time.If it is too soft, it may not withstand the

necessary multiple shocks occurring during handling, shipping, and dispensing.

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Friability (attrition-resistance test):  It's another measure of a tablet's strength.

 Why measure friability?

Tablets that tend to powder& fragment when handled:  1. lack elegance & consumer acceptance,  2. Create excessively dirty processes in areas of manufacturing as

coating & packaging.3.Can also add to a tablet's weight variation or content uniformity

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The laboratory friability tester is known as theRoche friabilator.  It subjects a number of tablets to the combined effects of

abrasion & shock by utilizing a plastic chamber that revolves at 25 rpm,

dropping the tablets with each revolution. A preweighed tablet sample is placed in the friabilator,

which is then operated for 100 revolutions.The tablets are reweighed.

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Tablets are then dusted and reweighed. Conventional compressed tablets that lose less than 1.0% of

their weight are generally considered acceptable. • % friability = (W0 – Wf / W0) x %.W0 = initial weight, Wf = final weight.

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Disintegration Test (U.S.P.):The U.S.P. device to test disintegration uses 6 glass tubes that are 3” long; open at the top and 10 mesh screen at the bottom end.

To test for disintegration time, one tablet is placed in each tube and the basket rack is positioned in a 1-L beaker of water, simulated gastric fluid or simulated intestinal fluid at 37 ± 0.5 C such that the tablet remain 2.5 cm below the surface of liquid on their upward movement and not closer than 2.5 cm from the bottom of the beaker in their downward movement.

Move the basket containing the tablets up and down through a distance of 5-6 cm at a frequency of 28 to 32 cycles per minute.

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Floating of the tablets can be prevented by placing perforated plastic discs on each tablet.

According to the test the tablet must disintegrate and all particles must pass through the 10 mesh screen in the time specified.

If any residue remains, it must have a soft mass.

Disintegration time: Uncoated tablet: 5-30 minutes

Coated tablet: 1-2 hours

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Dissolution is the process by which a solid solute enters a solution. In the pharmaceutical industry, it may be defined as the amount of drug substance that goes into solution per unit time under standardized conditions of liquid/solid interface, temperature and solvent composition.

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Dissolution is considered one of the most important quality control tests performed on pharmaceutical dosage forms and is now developing into a tool for predicting bioavailability, and in some cases, replacing clinical studies to determine bioequivalence. Dissolution behavior of drugs has a significant effect on their pharmacological activity. In fact, a direct relationship between in vitro dissolution rate of many drugs and their bioavailability has been demonstrated and is generally referred to as in vitro-in vivo correlation, IVIVC

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Apparatus-1 (Basket Type): A single tablet is placed in a small wire mesh basket attached to the bottom of the shaft connected to a variable speed motor. The basket is immersed in a dissolution medium (as specified in monograph) contained in a 1000 ml flask. The flask is cylindrical with a hemispherical bottom. The flask is maintained at 37±0.50C by a constant temperature bath. The motor is adjusted to turn at the specified speed and sample of the fluid are withdrawn at intervals to determine the amount of drug in solutions.

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Apparatus-2 (Paddle Type ): It is same as apparatus-1, except the basket is replaced by a paddle.

The dosage form is allowed to sink to the bottom of the flask before stirring.

For dissolution test U.S.P. specifies the dissolution test medium and volume, type of apparatus to be used, rpm of the shaft, time limit of the test and assay procedure for the API.

The test tolerance is expressed as a % of the labeled amount of drug dissolved in the time limit.

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PACKAGING: Blister Packs

 THERMOFORM BLISTERS – plastic base web– blister formed with aid of heating– low to high barrier – E.g. PVC

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COLD FORM BLISTER

– blister formed mechanically(no heat) – high barrier – E.g. Aluminium foil

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TROPICALSIDE BLISTER

– thermoform blister plus cold form tray– high barrier before use

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Thanks My Dear Students

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