Practical 6: Experiment 1 and 2

Procedures:

Experiment 1: Uniformity of diameter, thickness and hardness

1.      10 tablets were selected and tests for uniformity of diameter, thickness and hardness were tested using the Tablet Testing Instrument (PHARMATEST PTB 311).

2.       The deviation of individual unit from the mean diameter should not exceed ±5% for tablets with diameter of less than 12.5 and ±3% for diameter of 12.5mm or more.

Experiment 2: Tablet friability

1.      10 tablets 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 40 rpm, time to 10 minutes, and the operation is started.

3.      At the end of the operation, all the tablets are removed and the dust or powder is freed using a brush. The tablets are weighed. The percentage loss of weight is determined.

4.      Compressed tablets are not more than 1% of its weight.  

Results and calculations:

Experiment 1

Tablet	Thickness (mm)	Diameter (mm)	Deviation	Hardness
1	5.44	13.13	-0.01	150.17
2	5.37	13.12	-0.02	139.87
3	5.46	13.13	-0.01	145.37
4	5.40	13.19	+0.05	141.29
5	5.51	13.14	0	132.04
6	5.46	13.11	-0.03	126.89
7	5.44	13.12	-0.02	130.80
8	5.48	13.16	+0.02	177.90
9	5.38	13.14	0	137.38
10	5.51	13.10	-0.04	130.09
Average	5.45	13.14		141.18

Average diameter = 13.14mm

13.14mm x 3% =0.39mm

±3% of 13.14mm = 12.75mm - 13.53mm

Experiment 2

Before abrasion Weight (g)	After abrasion
	Weight (g)	Weight loss(g)	Weight loss(%)
6.8170	6.7963	0.0207	0.30

Compressed tablets lost 0.30% of their weight, which is not more than 1% of its weight. Hence, all the 10 tablets have passed the friability test. 

Discussion

One of the pharmacopoeial standards that should be followed by oral dosage forms is the test of uniformity of diameter. Based on the result obtained, the average diameter of tablet is 13.14mm. So, the deviation of individual unit from the mean diameter should not exceed 3% for tablets with diameter of more than 12.5mm. The result shows that all the tablets do not exceed the limit of standard percentage deviation, thus they are all acceptable. For the non-pharmacopoeial standards, we have tests for hardness and thickness of oral dosage forms. The tablet thickness depends on the diameter of the die, the amount of powder permitted to flow into the die and also the force exerted during compression process. Meanwhile, the hardness test measures the strength of pressure required to crush the tablet. Degree of hardness of tablets is determined by the strength of force applied during compression. Tablets should possess sufficient hardness to resist breaking during normal handling, packaging and transporting. At the same time they should also be soft enough to disintergrate after administered orally.

Physical instability in terms of friability is often related to various forces applied on tablets. Friction and shock are the most common forces that cause tablet to break or cap. Transportation and packaging of tablets often exposed tablets to these forces. In this experiment, the rotation of tablets in the tablet abrasion and friability tester subjects them to frictional forces. These frictions result in the tablets to being abraded, hence, loss some materials as well as weight

In this experiment, compressed tablets lost 0.30% of their weight, which is not more than 1% of its weight. Hence, these 10 tablets have passed the friability test. A thick tablet may have tendency to cap whereas thin tablets of large diameter often show extensive capping, thus indicating that tablets with greater thickness have reduced internal stress. (http://www.pharmainfo.net/tablet-evaluation-tests/mechanical-strength-tablets/friability) Hence, the 10 experimental tablets achieve appropriate thickness which gives them a higher friability. 

            Tablets which are too friable may cause undesirable effects, such as inaccurate dose, instability and wastage of money as well as resources. To prevent all these, friability test which is closely related to tablet hardness, is designed to evaluate the ability of the tablet to withstand abrasion in packaging, handling and transportation. During tablet manufacture, friability test should be correlated with actual stress experience. Packaged tablets also should subjected to cross-country shipping tests as well as to various drop tests.