friability test

A friability test measures how much a tablet crumbles when knocked about — a stand-in for the bumps and tumbling tablets get during coating, packaging, and shipping. You weigh a group of tablets, tumble them, then weigh them again; the weight lost as dust and chips is the friability.

The standard apparatus is a rotating drum (the friabilator) with a baffle that lifts and drops tablets a fixed number of times, usually 100 rotations at 25 rpm. Tablets are dedusted and weighed before and after, and percentage weight loss is calculated. A common acceptance limit for uncoated tablets is not more than 1.0 percent, with any capping, cracking, or breaking of tablets counting as a failure regardless of the number.

Friability reflects a tablet's mechanical strength at its surface and edges, and it sits alongside hardness as a measure of robustness. The two can trade off — a very soft tablet may be high in friability, while overly hard tablets can become more brittle or slow to disintegrate — so formulators balance them rather than maximizing either alone.