Guidelines for Tablet Friability Determination as per United States Pharmacopeia

Why Friability test is Performed – In this article we are going into detail about the friability test, how it is performed as per guidelines, the number of samples to be taken for testing, and reasons for performing the friability test.

Introduction: Let us start with the word friability, it is nothing but the tendency of a solid substance to break into smaller pieces or crumble under mechanical stress or pressure, in terms of tablets it is the process of evaluating how easily the tablets break when exposed to mechanical stress like during packaging, handling, and transportation. This test determines the Physical strength of tablets.

Friability Apparatus Specifications

• The friability apparatus should have the following characteristics:
  – Drum Material:  The drum should be made up of transparent synthetic polymer with polished internal surfaces, that should not be prone to static buildup.
  – Internal Diameter of Drum: It should be between 283 mm and 291 mm.
  – Drum Depth: It must be Between 36 mm and 40 mm.
  – Curved Projection: Inside radius between 75.5 mm and 85.5 mm, extending from the middle of the drum to the outer wall.
  – Drum Rotation Speed: 25 ±1 rpm.
  – Drum Orientation: The drum is attached to a horizontal axis.

Friability Test Process: 

According to the guideline if the weight of the tablet is less than or equivalent to 650 mg, take sample tablets whose weight corresponding to 6.5g

– For tablets weighing ≤ 650 mg each, use a sample of whole tablets totaling 6.5 g.
– For tablets weighing > 650 mg each, use a sample of 10 whole tablets.
– before performing the friability test dedust the tablets carefully.

Now weigh the tablets before placing them in the drum and note this as initial weight W1 place the tablets in the drum and run the apparatus for 4 minutes i.e. 25 revolutions per minute. After the test completion, collect the tablets dedust and reweigh them, this is the final weight W2

W1 – W2 / W1 *100 gives percent friability (Initial weight W1 Minus Final weight W2 divide by initial weight multiplied by 100)

 Evaluation:
– Inspect the tablets for cracks, cleaves, or breaks. If any are present, the sample fails the test.
– If the weight loss exceeds the acceptable value, repeat the test twice more and calculate the mean weight loss from the three tests.
– A maximum mean weight loss of not more than 1.0% is acceptable.

Special Considerations

Irregular Tumbling:
– If the tablet size or shape causes irregular tumbling, adjust the drum base to form an angle of about 10° with the bench top to ensure the tablets tumble freely without binding together.

Effervescent and Chewable Tablets: For these the test specifications may vary

Hygroscopic Tablets:  Conduct tests in a humidity-controlled environment as they observe moisture and gain weight, if test performed under normal conditions.

Note:  Drums with dual scooping projections or apparatus with multiple drums can be used for running multiple samples at a time.