Tablet Friability Test

A tablet can pass a hardness test and still fail friability. Hardness measures the force needed to crush a tablet. Friability measures how much material a tablet sheds when tumbled, which is closer to what happens in a coating pan, on a blister line and in a shipping carton. Breakage during coating, blistering and transport is exactly what the friability test is meant to predict.

That difference makes a failing result useful. It rarely means "press harder". It points to a binder, granule, lubricant or compression problem that a harder tablet can hide.

For a buyer, the result matters twice. It is a number on a batch record, and it is a clause in the contract that decides what happens when the number is bad.

USP <1216> tumbles about 6.5 g of tablets (or 10 tablets if heavier than 650 mg) in a drum for 100 rotations at 25 ±1 rpm, and weight loss of no more than 1.0% passes. The USP <1216> Tablet Friability harmonized chapter (official since August 1, 2023), the European Pharmacopoeia (Ph. Eur.) 2.9.7 method and the World Health Organization (WHO) International Pharmacopoeia use the same figures. The historical USP 32 text and BP 2012 method carry them too:

• Sample: for tablets of 650 mg or less, whole tablets as near as possible to 6.5 g. For heavier tablets, 10 tablets.
• Preparation: dedust the tablets before the run and after it.
• Drum: 283 to 291 mm in diameter and 36 to 40 mm deep, turning at 25 ±1 rpm for 100 rotations in total (about 4 minutes), not 100 per minute.
• Calculation: friability (%) = (W1 − W2) ÷ W1 × 100, where W1 is the starting weight and W2 the weight after tumbling and dedusting.
• Pass: run once. Weight loss of no more than 1.0% passes. If the loss is above 1.0% or the result is hard to read, repeat twice and take the mean of the three runs; the mean must be no more than 1.0%. Any obviously cracked, cleaved or broken tablet fails the sample.
• Adjustments: if tablets bind together, tilt the drum base about 10°. Hygroscopic tablets (those that absorb moisture) need a humidity-controlled room.

Check the current USP–NF wording before fixing a specification.

At 1.0%, a 6.5 g sample may lose 65 mg, and a 10-tablet sample of heavier tablets may lose 1% of its own mass. The table applies the USP sample-size rule above, with the allowance taken as 1.0% of sample mass.

One chipped corner against the 1.0% allowance

Three consequences follow:

• One 250 mg tablet that loses a 30 mg corner accounts for 30 ÷ 6,500 = 0.46% of the sample, almost half the allowance.
• One 650 mg tablet that loses 65 mg uses the entire allowance.
• Three runs of 0.6%, 0.9% and 1.3% average 0.93%. The mean passes even though one run exceeded the limit, and any visibly broken tablet still fails the sample whatever the weight loss.

A failure often means particles are poorly bonded at the tablet surface or edges. The usual culprits are the binder, granule quality, lubricant level and press settings. Raising hardness is not the cure, because past a point it slows disintegration and dissolution. The causes below, and the point about hardness, come from formulation experience, not a pharmacopoeial rule. One failing batch still needs an investigation to confirm which cause applies.

Fast-dissolving products make this trade-off sharper. A dispersible tablets guide explains why they are compressed at lower hardness.

The in-process checks listed in 21 CFR 211.110(a) name weight variation, disintegration and dissolution, not friability or hardness. Friability becomes a requirement because the buyer's specification and agreement say so.

Put the method, limit, retest rule, test stage, exceptions and records in the specification, and put out-of-specification handling in the quality agreement. FDA's quality agreement guidance says the agreement should state which party carries out each CGMP (current good manufacturing practice) activity. A pharmaceutical quality agreement covers the wider document.

Paste-ready lines:

1. Method: "Friability per USP <1216>: 25 ±1 rpm, 100 rotations; about 6.5 g if unit weight is 650 mg or less, otherwise 10 tablets; dedusted before and after." Pass: the batch record shows each parameter.
2. Limit: "Weight loss NMT (not more than) 1.0% on a single run, or on the mean of three runs if repeated. Any cracked, cleaved or broken tablet fails." Pass: the record shows the result and a visual check.
3. Retest rule: "A single run above 1.0% triggers three runs; each run and the mean are reported." This is recommended, because the mean alone can hide one bad run.
4. Stage: state whether friability is checked in-process at compression (with frequency), at release, or both. Pass: the frequency is a number, not "periodically".
5. Exceptions: name coated, chewable, effervescent and hygroscopic products, each with its own limit and conditions. Pass: each listed product type has its own written limit and test conditions. Fail: a coated or chewable product is covered only by the 1.0% default.
6. Records: friabilator (the tumbling-drum instrument) ID, balance ID, tablet count, and before and after weights. Pass: the batch record contains all five fields for every run.
7. Out of specification: who investigates, within how many days, and who decides lot disposition (the decision to release, rework or reject a batch). Pass: the clause names an owner, a day limit and a lot-disposition decision-maker.

Not automatically. The 1.0% limit applies to most products; USP says chewable and effervescent tablets may have different specifications, and Ph. Eur. 2.9.7 covers uncoated tablets only. For a coated product, it is recommended to agree in writing whether friability is tested on the cores before coating or on the finished tablet, and what limit applies.

We offer tablets within our oral-dose CDMO (contract development and manufacturing organization) services, from product development through commercial manufacturing. Our route runs from inquiry to feasibility review, commercial quotation, development or technical transfer, production and quality control, packaging and dispatch. Put your friability clause in the first inquiry so it is on the table from the start.

Send the strength, unit weight, coated or uncoated status and your clause through our contact form. See third party manufacturing pharma and pharmaceutical technology transfer for what to prepare.