Pharmaceutical Technology: TABLET FRIABILITY

Aim:

To test the friability of 10 same randomly selected tablets.

Introduction:

Friction and shock are the forces that most often cause tablets to chip, cap or break. The friability test is closely related to tablet hardness and is designed to evaluate the ability of the tablet to withstand abrasion in packaging, handling and shipping. It is usually measured by the use of the Roche friabilator. The tablet is tumbled in a rotating drum. A number of tablets are weighed and placed in the apparatus where they are exposed to rolling and repeated shocks as they fall 6 inches in each turn within the apparatus. With this equipment it is possible to measure in two modes: a specific time interval or a specified number of rotations. After four minutes of this treatment or 100 revolutions, the tablets are weighed and the weight compared with the initial weight. The loss due to abrasion is a measure of the tablet friability. The value is expressed as a percentage. A maximum weight lossof not more than 1% of the weight of the tablets being tested during the friability test is considered generally acceptable and any broken or smashed tablets are not picked up. Normally, when capping occurs, friability values are not calculated. A thick tablet may have less tendency to cap whereas thin tablets of large diameter often show extensive capping, thus indicating that tablets with greater thickness have reduced internal stress.

Experimental methods:

1. 10 tablets of Ettrocin are selected and weighed.

2. All tablets are put into the drum of the tablet abrasion and friability tester. The rate of rotation is set to 100 rpm, time to 10 minutes and the operation is started.

3. All the tablets are removed and freedom of dust or powder are ensured at the end of the operation.

4. Not more than 1% of the weight of the compressed tablet should lose.

Chemicals and apparatus:

Weighing boat, 10 tablets of Ettrocin, analytical balance,brush

Results and calculation:

	Total weight of 10 tablets (g)
Before friability test	6.5777
After friability test	6.5258

Percentage of weight loss after friability test

Total weight of 10 tablets (before) – total weight of 10 tablets (after)

= 6.5777g – 6.5258g

= 0.0519g

Weight loss/original total weight of the 10 tablets x 100%

= 0.0519g/6.5777g x 100%

= 0.79%

Discussion:

Based on the result of this experiment, the weight loss of the 10 tablets due to the mechanical abrasion does not exceed 1% which is still within the acceptable range. Once the percentage of weight loss of the tablets exceeds 1% if compared to the original one, the tablets are considered fail the friability test and thus show that the tablets are not in good quality. Undoubtedly, there should not be any broken tablets.

Some of the tablets produced by the industry are friable due to the application of mechanical action. The friability of the tablets are caused by a few reasons. One of them is due to insufficient or non effective binders used in tablet formation. The insufficient or non effective binders normally require high compression forces to hold the particles together. Lower compression forces may not be enough to bond particles together and causing friability failure. When a tablet is ejected it expands. If the expansion is too rapid, or too great the particles of the tablets may break apart. A common fix is to add a taper in the die to allow for a more gentle release to enhance the friability of the tablets. Besides that, entrapped air can cause the tablet to break apart. Slowing the press will extend dwell time and give the air more time to escape. Press speed and the amount of clearance between the upper punch tip and the die also contributes to the air release. For many powders increasing the venting by increasing the taper or increasing the tip/die clearance, slowing the machine down, and using pre-compression correctly all contribute to improved friability. Die wear rings can cause friability issues. Make certain dies are inspected and replaced when wear rings are detected. Polished punches and a formula with a well blended lubricant can contribute to the better friability of a tablet.

Some errors might be occurred throughout this experiment. After tumbling the tablets in the rolling drum, the dust or powder which stick on the surface of the tablets cannot be seen clearly by the naked eyes and thus they cannot be removed thoroughly which will affect the result of the experiment. Besides that, while rolling in the drum, some of the tablets stick on the surface of the rolling drum can cause inaccurate results since not all the tablets are subjected to the mechanical abrasion for the same frequency.

Conclusion:

The friability of the tablets can be tested using the rolling drum which is set to specific rotation speed and specific time. The percentage of the weight loss of tablets after testing should not be more than 1%. If it does happens, the tablets is considered fail and of poor quality.

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