Friability Testing of Tablets

The tablets manufactured by a firm needs to be sufficiently hard to bear the shocks experienced during their packing and transit. Measuring tablet hardness does not reliably indicates the tablet strength as too hard tablets also experience capping or lose their crown portions on attrition leading to chipping or fragmentation. Hence, friability testing of tablets is an important requirement. The friability test is performed on uncoated compressed tablets. Friability test is intended to measure the physical strength of the tablet. Measurement of tablet friability supplements other physical strength measurements, such as tablet breaking force.

In friability test the tablets are prone to abrasion hence enabling us to check for the tablet strength under application of force in different manner. Friability testing involves repeatedly dropping a sample of tablets over a fixed time, using a rotating drum with a baffle. The result is inspected for broken tablets, and the percentage of tablet mass lost through chipping. The difference in tablet mass lost (in percentage) accounts for the extent of friability of tablets manufactured.

Apparatus: The Tablet Friability apparatus is used for testing. This apparatus consists of a drum of transparent synthetic polymer with polished internal surfaces and is subject to minimum static build-up. One side of the drum is removable. It has a curved projection which extends from the middle of the drum to the outer wall, enabling the tumbling of the tablets at each turn of the drum. The drum is attached to the horizontal axis of a device. It rotates at 25 ± 1 rpm.  The other specifications are as follows:

Fig. Tablet Friability Apparatus

Sample Quantity: For tablets with a unit weight equal to or less than 650 mg, take a sample of whole tablets corresponding as near as possible to 6.5 g. For tablets with a unit weight of more than 650 mg, take a sample of 10 whole tablets.

Method: Accurately weigh the tablet sample, and place the tablets in the drum. Rotate the drum 100 times, and remove the tablets. Remove any loose dust from the tablets as before, and weigh them accurately. The test is run only once unless the results are difficult to interpret or if the weight loss is greater than the targeted value, in which case, the test is repeated twice and the mean of the three tests is determined.

Calculation:

Where,

Winitial is the weight of tablets before the test (in mg)

Wfinal is the weight of tablets after the test (in mg)

Acceptance Criteria: A maximum mean weight loss from the three samples of not more than 1.0% is considered acceptable for most products.

Special Consideration:

1. It should be ensured that with every turn of the drum the tablets roll or slide and fall onto the drum wall or onto each other.
2. The sample fails the test if obviously cracked, chipped or broken tablets are present in the sample.
3. Dedust tablets carefully prior to testing.
4. If tablet size or shape causes irregular tumbling, adjust the drum base so that the base forms an angle of about 10° with the horizontal and the tablets no longer bind together when lying next to each other, which prevents them from falling freely.
5. Effervescent tablets and chewable tablets may have different specifications as far as friability is concerned.
6. Appropriate humidity-controlled environment shall be provided for testing of hygroscopic tablets.

Drums with dual scooping projections, or an apparatus with more than one drum, for the running of multiple samples at one time, are also permitted.

The friability testing method is almost harmonized across all the pharmacopoeias viz. USP, EP, JP etc.

References:

1. The International Pharmacopoeia – Ninth Edition, 2019
2. USP <1216> Tablet Friability

Stay tuned for info on friability testing of granules and spheroids