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4.30 FRIABILITY OF UNCOATED TABLETS

      This test is intended to determine, under defined conditions, the friability of uncoated tablets, the phenomenon whereby tablet surfaces are damaged and/or show evidence of lamination or breakage when subjected to mechanical shock or attrition.

Apparatus

      Use a drum with an internal diameter between 283 and 291 mm and a depth between 36 and 40 mm, made of a transparent synthetic polymer with polished internal surfaces and not subject to static build-up (Fig. 1). One side of the drum is removable. The tablets are tumbled at each turn of the drum by a curved projection with an inside radius between 75.5 and 85.5 mm that extends from the middle of the drum to the outer wall. The outer diameter of the central ring is between 24.5- 25.5 mm. The drum is attached to the horizontal axis of a device that rotates at 25±1 rpm. Thus, at each turn the tablets roll or slide and fall onto the drum wall or onto each other.

Procedure

      For tablets weighing up to 0.65 g each, take a sample of 20 tablets; for tablets weighing more than 0.65 g each, take 10 tablets. Place the tablets on a No. 1000 sieve and remove any loose dust with the aid of air pressure or a soft brush. 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. If no tablets are cracked, split or broken, weigh the tablets to the nearest milligram.

      In general, the test is run once. If the results are doubtful or if the weight loss is more than 1 per cent, repeat the test twice and determine the mean of the three tests. A maximum loss of 1 per cent of the weight of the tablets tested is considered to be acceptable for most products.

      For tablets having a diameter of 13 mm or more, problems of reproducibility may be encountered due to frequent irregular tumbling. In such cases, adjust the drum so that the tablets may fall freely and do not bind together when lying next to each other, adjusting the drum, so that the axis forms a 10º angle with the base, is usually satisfactory.

      Effervescent tablets and chewable tablets may have different specifications as far as friability is concerned. In the case of hygroscopic tablets, an appropriate humidity-controlled environment is required for testing.

      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.

Expression of the Results

      The friability is expressed as the loss of mass and it is calculated as percentage of the initial mass. Indicate the number of tablets used.