Chipping Away at the Preventable Causes of High Friability
September 26, 2017
Imagine the perfect tablet. No chipping, crumbling or breaking, batch after batch. At Colorcon, we can help make that a reality with a little up-front planning and insight from the experts. As with any tablet core formulation, the properties of the API, excipient choices (including the film coating selection) and manufacturing processes all play a role in determining whether your batch may be prone to low or high friability issues. Let’s take a look at how we can mitigate friability issues and improve your batch outcomes.
First, let’s see what’s at the center of it all: The Core
Addressing tablet hardness and tablet disintegration is important. We have seen many cases of “extreme formulation,” compressing extremely hard and then needing to add superdisintegrant. High levels of superdisintegrants can lead to higher moisture uptake and higher raw material costs.
With our depth of experience at Colorcon, we recommend taking a more moderate approach, compressing to result in a consistently hard (but not too hard) tablet with reliable quick disintegration, that doesn’t require huge amounts of superdisintegrant, if any.
Good tablet hardness comes from choosing the right excipients, and a combination of MCC with Starch 1500® partially pregelatinized maize starch, creates a balance of hardness and disintegration.
It's also good practice to perform regular inspection and maintenance on punches and tooling. Worn punches can adversely affect the strength of the sensitive tablet edges, causing chipping.
Shape and design can also play a role in the strength and friability of the tablet. Rounder shapes will move evenly and be exposed to less stress during the coating process than elongated shapes with flat/sharp edges.
Next up: The Coating
Aside from making it “appealing,” film coating strengthens and protects the tablet. And if your core is friable from the beginning, you’re going to need some special protection. Your choice of film coating can literally make or break the finished product, so choose wisely.
Advances in film coating technology using polymers, like polyvinyl alcohol (PVA) or PVA-PEG copolymer, improve adhesion to cores — even those with waxy substrates. With the advantage of high productivity, the coating process time is significantly faster than traditional HPMC-based systems, so your core is exposed to the rigors of coating for less time while still resulting in a perfect finish.
So, connect with us early in the formulation process to help you choose the right coating for your product.
Finally, let’s examine: The Process
It’s not uncommon for coating challenges to reveal themselves only during scale-up; a coating that worked perfectly well during development becomes problematic during commercial scale up.
When moving into larger scale coating pans, it is important to remember that deeper tablet beds mean more tablets on top of each other, which puts greater and sometimes damaging stress on the product.
Some may think that the “simple fix” here is to reduce the pan load — putting in fewer tablets. However, many coating pans are optimized for a certain fill level, and the tablets won’t flow and mix correctly without enough fill. This can bring on a completely new set of problems including decreased process efficiency, poor coating uniformity, or picking and sticking of the tablets.
If all else fails (or it’s too late to change anything else), there are a few process adjustments you can use. When coating friable tablets, the initial protective layer should be applied as quickly as possible. That means you can spray faster for the first third of the process to get some coating protection on fast; then slow down the spray rate to “normal” to make sure you still get the coating uniformity you need.
At Colorcon, our goal is to help our customers make every tablet a perfect tablet, every time. Reducing friability and maintaining product quality are best achieved when we connect with you early and understand first-hand the challenges your formulation, coating and manufacturing process may present.
