Tablets & Capsules September 2013 …

1 IAs appeared in Tablets & Capsules September tablet defectsMatthew KnoppEditorTablet defects bedevil many manufacturers. This article outlinessome strategies that tablet production experts use to resolve themost common ones, including weight variation, black spots,capping, and sticking and the condition of the tablet press (settings, worncomponents) and changes to raw materials (particle sizeand shape, segregation, moisture). Changes in the envi-ronmental temperature and humidity can also have aneffect. At the press, weight variation can stem from anumber of causes, including improper feeder or compres-sion settings; worn punches, die pockets, or punchguides; and temperature changes during a May, about 90 people gathered in Cleveland to gaininsight on tablet defects from a panel of experts.

2 Led byMike Tousey of Techceuticals, the panel included JimMossop, project manager at Fette Compacting America;Ed Godek, manager of process technology at Glatt AirTechniques; Fabrianno Ferrini, product manager at IMAN orth America; Fred Murray, president of Korsch America;and Dale Natoli, president of Natoli most common defects include variations in weightand potency, black spots, capping, and sticking and pick-ing. Others include lamination, mottling, excessive friabil-ity, chipping, flashing, and variation in content weight control is the cornerstone of tabletproduction, and common causes of weight variationThe symposium, led by Mike Tousey, took place May 21-22 in Cleveland,OH. Panelists included Dale Natoli, Fabriano Ferrini, Jim Mossop, EdGodek, and Fred CSC PublishingTablet weight and the feeder assemblyWeights can vary if the paddle feeder overworks thepowder and changes its characteristics, Mossop said.

3 Hisrule of thumb is to operate the feeder and tail-over-die sothat 80 percent of the powder remains in the die, and 20percent is pushed back. So with 10-millimeter fill cam,you d fill 8 millimeters of powder, or something to thateffect. If the fill is too deep, you re pushing back too much,and it gets overworked. Headded that the condition ofthe scraper blade and tail-over-die are critical but oftenoverlooked. I had someoneask me, Oh, we need tochange them? These are important components and theyare not expensive. He said that he prefers scraper bladeswith a knife edge over those with a square edge for prod-ucts that have a tendency to stick to the die table that wear too quickly may be due to die-tablerun-out, Natoli said. The table is not always true, and it snot always a mirror finish.

4 You need to check those hori-zontal surfaces and identify the high spot. Set the feederscraper to that. In most cases, the clearance should inch, he said, and the scraper s springs should applylight, even pressure to the die table. Murray said a clearance is a good place to start. But if theproduct is prone to extrude under the feeder, it may haveto be higher. He also recommended verifying that thedies are set to the proper depth. High dies can destroythe scraper in the first 5 minutes of the batch. Conversely, dies set too low or a scraper set too high willallow powder to bypass the scraper and cause other prob-lems, including weight variation, he weight: The link to potency and blend characteristicsTousey asked participants whether tablet weight andtablet potency were intertwined, because in a uniformblend or granulation, any under- or over-weight tabletswould be inherently sub- and super-potent.

5 Yet only afew participants linked the two issues. One was anattendee whose company makes dietary supplements. We have to go with weight to meet label claim, shesaid. We don t test all those [ingredients] for contentuniformity, but we do test weights so we can say that wemeet it. That led to a discussion of blending and how segrega-tion affects content uniformity and/or potency. Youcould have a blend meet spec at plus or minus percentand not get the required potency, said Godek, who oftenworks with fluid bed processors. A lot of APIs and granu-lations are not under control, and many fines are super-potent. It comes down to how the process is run. Fluidbeds are also good air classifiers if you re not careful. Another participant agreed that data gathered from theblend don t always correlate to what happens on the described taking samples from a blending bin thatfailed uniformity testing, but ran 100 percent good whenput on the press.

6 To save the batch, the company demon-strated to the FDA its satisfactory performance on a sin-gle-station hydraulic press. They bought into it, he truth, Tousey said, there is little tablet press opera-tors can do to change a blend s characteristics, be it segre-gation, excessive fines, moisture content, or some otherproperty. You do what you can to save the batch byadjusting the press. There s no such thing as a perfectblend. Think of it like shuffling cards. He also saidblends can perform differentlydepending on how longthey ve predicted thattablet press operators won thave to worry about tablet weights thanks to better tech-nology. Weight adjustment will go by the wayside in theyears to come. You ll be able to detect API and makechanges on the fly. It s a few years out but it s going tocome.

7 Tablet weight and toolingNatoli said accurate weights require that the punches,especially the lower punches, are the correct workinglength. He defined that as the distance from the lowestpoint of the punch-face cup to the head flat and said itshould be within inch of specification. Thus,within a set of punches, the difference between the work-ing lengths of the longest and shortest punches should beno more than inch. He also recommended separat-ing the upper and lower punches and verifying the work-ing length of new punches added to an old set. As long asit s within tolerance, a new tool will be fine 95 percent ofthe time, he tablet diameters of 5 millimeters or less, Natolirecommended generating a tool-matching report andpairing the longest upper punch with the shortest lowerpunch. That s the best scenario for hardness, thickness,and weight control.

8 The dies, he said, don t contribute toweight also addressed the importance of the punchworking length. You have to understand how the punchworking length can impact the press force control sys-tem, which provides automatic tablet weight tool tolerances will affect the measured compressionforces and cause the control system to react to toollength variation instead of actual tablet weight variation. Black spotsThe term black spots (photo, page 14) covers manydifferent defects in tablet appearance. It could be asmudge not a spot, gray not black, or within the tabletnot on the surface. A better term, one attendee suggested,is dark visual defects (DVDs), and people used bothterms. The causes of DVDs are legion, Tousey said, but ifthey appear on the tablet surface, they likely came fromthe press, not the formulation.

9 Indeed, the design andcondition of the tooling and press dominated the discus-sion of data don t always correlate to what happens on the CSC PublishingNatoli said it s normal for powders, over time, toabrade the tooling and other areas they contact, but onlyrarely usually because of a poor choice of steel is thetooling itself the source of DVDs. More often, blackspots result when abrasive wear expands the clearancebetween the punch and die, entrapping particles. Thoseparticles accumulate on the die wall and turn dark fromthe heat of friction. At some point, the punch scrapes offa portion of the burnt material and it s deposited on cleaning and over-polishing the tooling by drag finisher or by hand can produce a similar result,Natoli said. You can round off corners, the lower relief,and the lower punch tip itself, he said, which allows par-ticles to wedge between the punch and die and createsblack spots.

10 When black spots appear, check the condi-tion of the punches and dies, he prevent heat-induced DVDs, some companiesinstall vortex coolers under the die table, Mossop the entire room is another option, but successwith that approach depends on the operators followingproper procedure. It s only good when the doors areclosed and you re not stopping and starting the machine, he punch-guide seals are another source of blackspots, and testing them for wear is easy, Tousey said. Ifthe punch falls out under its own weight, the punch sealis worn out. It should hold the punch by itself and act asa squeegee during operation. While the seals can becleaned, take care, Natoli said. The brushes for punchguides are not healthy for cleaning punch seals. Iwouldn t use them. Mossop agreed that the seals deserveattention.